Location: MSHCP > VOLUME 2 > MAMMALS
Aguanga kangaroo rat (Dipodomys merriami collinus)
State: None
Federal: None
The Aguanga kangaroo rat has a narrow distribution within the Plan Area, with known localities including Temecula Creek in the Aguanga area and Wilson Creek in the Sage area. The Aguanga kangaroo rat typically is found in Riversidean alluvial fan sage scrub, but may occur in Riversidean sage scrub, chaparral and grassland in uplands and tributaries in proximity to Riversidean alluvial fan sage scrub habitats. Conservation of Riversidean alluvial fan and upland sage scrub in Temecula and Wilson creeks is essential for conservation of this species in the Plan Area. Monitoring and adaptive management to maintain and enhance habitat in these areas also will be important for this species because of the small amount of remaining habitat. The Aguanga kangaroo rat is a Group 3 species because of its narrow distribution in the Plan Area and the need for population monitoring and adaptive management.
The Aguanga kangaroo rat is on the Additional Survey Needs and Procedures (Section 6.3.2) list and surveys for the species will be conducted as part of the project review process for all public and private projects within the mammal species survey area where suitable habitat is present (see Mammal Species Survey Area Map, Figure 6-5 of the MSHCP, Volume 1). Aguanga kangaroo rat localities found as a result of survey efforts shall be conserved in accordance with the procedures described within Section 6.3.2, MSHCP, Volume 1.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 5,484 acres (81 percent) of occupied or suitable habitat within the historic flood plains of Temecula Creek and Wilson Creek, and their tributaries.
Surveys for Aguanga kangaroo rat will be conducted as part of the project review process for public and private projects within the mammal species survey area where suitable habitat is present (see Mammal Species Survey Area Map, Figure 6-5 of the MSHCP, Volume 1). Aguanga kangaroo rats located as a result of survey efforts shall be conserved in accordance with the procedures described within Section 6.3.2 of the MSHCP, Volume 1.
Within the 5,484 acres of occupied and suitable habitat in the MSHCP Conservation Area, ensure that at least 75 percent (4,113 acres) of the total is occupied and that at least 20 percent of the occupied habitat (approximately 823 acres) supports a medium or higher population density (≥5 to 15 individuals per hectare; based on McKernan 1997 studies of the San Bernardino kangaroo rat) of the species as measured across any 8-year period (i.e., the approximate length of the weather cycle).
Within the MSHCP Conservation Area, Reserve Managers shall maintain or, if feasible, restore ecological processes within the historic floodplains of Temecula Creek and Wilson Creek, their tributaries, and other localities within the Criteria Area where the Aguanga kangaroo rat is detected in the future, given existing constraints and activities covered under the Plan. Maintenance and/or restoration of ecological processes within the MSHCP Conservation Area may include 1) allowing for natural dynamic fluvial processes of flooding, scouring and habitat regeneration, and possibly fire, to maintain healthy alluvial fan sage scrub habitat, 2) careful planning and design of existing and future authorized uses that may affect natural processes such as flood control, water conservation, and sand and gravel mining, 3) control of other uses and disturbances such as farming and discing for weed abatement, heavy grazing, off-road vehicles, and vandalism, and 4) control of invasive exotic species.
Few documented locations are available for the Aguanga kangaroo rat. The known locations are associated with Temecula and Tule creeks in the Aguanga Valley near the junction of Highway 79 and Highway 371 and a separate location along Wilson Creek south of Wilson Valley Road and northwest of Billy Goat Mountain in the Gonzalez Conservation Bank area. For the purpose of the conservation analysis, suitable habitat for the Aguanga kangaroo rat includes chaparral, Riversidean sage scrub, desert scrub, grassland, and Riversidean alluvial fan sage scrub within and adjacent to drainages in the southeastern portion of the Plan Area, including Temecula Creek, Tule Creek, Wilson Creek, Kolb Creek and Arroyo Seco. Based on these assumptions about habitat, the Plan Area supports approximately 6,800 acres of suitable habitat for the Aguanga kangaroo rat. Table 1 shows the conservation of suitable habitat for the Aguanga kangaroo rat. Overall, approximately 5,484 acres (81 percent) of suitable habitat in the Plan Area would be in the MSHCP Conservation Area. Most of the conserved habitat is along Temecula Creek in the Aguanga, Radec, and Butterfield valleys and along Wilson Creek between Wilson Valley Road and Vail Lake.
Little is known about the populations and distribution of the Aguanga kangaroo rat in the Plan Area. The Temecula Creek and Wilson Creek populations are separated by rugged upland terrain unlikely to be used by dispersing individuals, except for a possible habitat connection where the two creeks converge at Vail Lake. While the populations probably were connected historically at this location, whether suitable habitat physically connects the two populations at this point is unknown. The continuity and connectivity of the populations within the two creeks also is unknown. Within Temecula Creek, suitable habitat occurs in the Aguanga, Radec and Butterfield valleys, but the status of the habitat connections between the valleys where the creek narrows and is bordered by steep canyons is unknown. It may be assumed that the kangaroo rat could use these connections for dispersal, even if they are not suitable as live-in habitat, but their actual use as dispersal corridors is unknown. Likewise, within Wilson Creek the known populations occur along the creek south of Wilson Valley Road. The creek between this population and Vail Lake includes several potential obstacles to occupation and dispersal, including a narrow, steeply descending canyon between the occupied area and the Lancaster Valley and rural residential development and agriculture in the Lancaster Valley and the valley west of Sage Road to Vail Lake.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
AGUANGA KANGAROO RAT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 2,823 | 2,069 | 178 | 2,247 | 36 | 540 | 576 |
| Riversidean Sage Scrub | 1,475 | 1,396 | 1 | 1,397 | 7 | 71 | 78 |
| Desert Scrub | 281 | 281 | 0 | 281 | 0 | 0 | 0 |
| Riversidean Alluvial Fan Sage Scrub | 681 | 660 | 0 | 660 | 0 | 21 | 21 |
| Grassland | 1,548 | 894 | 5 | 899 | 4 | 645 | 649 |
| TOTAL | 6,808 | 5,300 78% |
184 3% |
5,484 81% |
47 <1% |
1,277 19% |
1,324 19% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
In summary, the MSHCP Conservation Area will include at least 5,484 acres (81 percent) of suitable habitat. Most of this habitat will be in the Wilson Creek and Temecula Creek drainages. Although the total acreage of suitable habitat conserved is not large, it does comprise 81 percent of identified suitable habitat in the Plan Area and includes the two known occupied areas. With implementation of the MSHCP, populations of the Aguanga kangaroo rat should remain viable in the Plan Area.
Approximately 1,324 acres (19 percent) of suitable habitat for the Aguanga kangaroo rat would be outside the MSHCP Conservation Area. No currently known populations of the Aguanga kangaroo rat would be subject to Incidental Take.
There are few specific studies of the subspecies Aguanga kangaroo rat (D.M. collinus), but there is a substantial literature for the species D. merriami. The information presented in this section largely is for the full species, with specific reference to the Aguanga kangaroo rat where appropriate.
The MSHCP data for the subspecies Aguanga kangaroo rat are limited, with only five recorded locations in the database. Although only one of the locations has a precision code (i.e., a precision of 2 north of Highway 79 and east of Sage Road), the remaining MSHCP data points are localized in the Aguanga/Sage area near the junction of Highway 79 and Highway 371. A sixth known location is along Wilson Creek just south of Wilson Valley Road and northwest of Billy Goat Mountain (DUDEK 1995). Based on the known quality of habitat in the vicinity of the recorded locations, the point locations in the database appear to be accurate and likely reflect existing conditions. However, little else is known of the distribution of this subspecies in Riverside and San Diego counties. Although the Aguanga kangaroo rat appears to be associated with sandy washes and drainages, the importance of adjacent uplands is unknown. This subspecies probably occurs in alluvial fan sage scrub habitat that is not under the jurisdiction of the ACOE (i.e., within the ordinary high water mark of dry washes) or CDFG. In addition, the taxonomic relationship between the Aguanga and San Bernardino kangaroo rats needs to be clarified.
Based on the habitat present in recorded locations, the Aguanga kangaroo rat, a subspecies of the Merriam's kangaroo rat (Dipodomys merriami), appears to be associated with Riversidean sage scrub, chaparral, redshank chaparral and non-native grassland. For example, the Aguanga kangaroo rat population along Wilson Creek was found in Riversidean sage scrub immediately adjacent to the creek. Dominant vegetation in the area was brittlebush (Encelia farinosa), California buckwheat (Eriogonum fasciculatum), coastal sagebrush (Artemisia californica), and cholla (Opuntia sp.).
Soil texture probably is a primary factor in this subspecies' occurrence. Sandy loam substrates allow for the digging of simple, shallow burrows. D. merriami, and other kangaroo rat species, actively avoid rocky substrates (Brown and Harney 1993). The soils at the Wilson Creek site are Gorgonio sandy loam and Hanford coarse sandy loam (Knecht 1971). These are the dominant soils along Temecula Creek near Aguanga as well. Both soils developed in alluvium made up of granitic material.
According to Hall (1981), the species D. merriami occupies a broad range of grasslands and arid habitats in southwestern North America, extending from northwestern Nevada southward through southeastern California, Baja California and in mainland Mexico south to northern Sinaloa. It ranges eastward to southeastern Utah, western and southern Arizona, central and southern New Mexico, and into western Texas.
The subspecies Aguanga kangaroo rat occurs in eastern San Diego County in the San Felipe, Earthquake, and Mason valleys (Williams et al. 1993). Within Riverside County the Aguanga kangaroo rat occurs in the Aguanga Valley and Wilson Creek north of Radec, and probably is scattered throughout sandy wash areas in the region west of the Anza Valley, particularly in Temecula Creek and tributaries east of Vail Lake (P. Behrends, pers. comm.). This subspecies probably also occurs in additional areas of northern San Diego County where there is potential habitat south along Temecula Creek toward Warner Springs, Cottonwood Creek, and Long Canyon.
Aguanga, Sage, Temecula Creek, Wilson Creek.
Same as above.
Genetics: Williams et al. (1993) provides descriptions for 19 subspecies of D. merriami. Patton and Rogers (1993a, 1993b) provide reviews of what is known of the cytogenetics (e.g., chromosomal variation) and biochemical genetics (e.g., isozyme and allozyme analyses, DNA sequencing) of heteromyid rodents, the rodent family to which D. merriami belongs. Patton and Rogers generally conclude that the understanding of heteromyid genetics is still relatively poor, the data are uneven, and that few studies have applied recent technical developments (e.g., DNA fingerprinting and sequencing). As of 1993, the only biochemical technique applied to heteromyids is protein electrophoresis, a relatively crude analytic tool by today's standards. Of interest to conservation planning would be any information relating genetics to habitat fragmentation and isolation, demography, habitat tolerance, and speciation. Unfortunately, very little information in the literature is available to address these issues.
D. merriami has 52 chromosomes and there is no reported karyotypic variation in the species (Patton and Rogers 1993a). The proportion of gene loci that are polymorphic among individuals ranges from 0.06 to 0.16 and the mean proportion of loci that are heterozygotic within individuals ranges from 0.00 to 0.061. These values, as well as values for other kangaroo rat species, are relatively low compared to other mammals (Patton and Rogers 1993b). (Patton and Rogers [1993b] caution that these summary statistics probably contain large sampling error as well as other important sources of error that limit their interpretation. Also, protein electrophoresis cannot provide the fine-grain genetic analysis possible with DNA fingerprinting and other recent techniques.) Studies of electromorphic distance for D. merriami also indicate high degrees of genetic similarity. There are no genetic studies of different populations of the Aguanga kangaroo rat to address the effects of habitat fragmentation and isolation, demography, or other issues relevant to conservation planning.
The only genetic demographic study of D. merriami identified by Patton and Rogers (1993b) was a study of spatial relationships among individual genotypes in a population of D. merriami on a 10-acre study site near Kramer, California by Johnson and Selander (1971). This study concluded, in Patton and Rogers' words, "that spatial clustering of genotypes was evident at two loci, and suggested that local structure, including the possibility of inbreeding, may characterize local kangaroo rat populations." page 264. However, their findings did not include statistical corroboration of this finding and these results must be interpreted as very preliminary.
Diet and Foraging: Many studies have reported on the diet of D. merriami (see Reichman and Price 1993 for a comprehensive review), but no specific studies have been conducted on the Aguanga kangaroo rat. Nonetheless, it is unlikely that the Aguanga kangaroo rat exhibits meaningfully different feeding patterns compared to other subspecies of D. merriami that would be relevant for conservation planning. D. merriami are primarily granivores (seed eaters), but they ingest herbaceous material and insects when available (Bradley and Mauer 1971; Reichman and Price 1993). They collect seeds from the substrate into fur-lined cheek pouches for transport and then store them in scattered surface caches in the vicinity of their home burrows for later retrieval and consumption (Daly et al. 1992a). Unlike some larger kangaroo rat species (e.g., D. spectabilis), D. merriami do not hoard seeds to a central location (i.e., larder hoarding). Bipedal locomotion in kangaroo rats allows them to travel large distances over open ground very quickly and exploit widely scattered food sources.
Daily Activities: D. merriami, and all other kangaroo rats, are primarily nocturnal animals, but they also exhibit crepuscular behavior around dusk and dawn. They emerge from their day burrows around dusk to engage in foraging and other activities. Animals may be active any hour of the night, but the heaviest concentration of activity tends to occur in the three to four hour time span just after dusk. They usually return permanently to their day burrows before dawn (Behrends et al. 1986a). Factors affecting the amount and patterns of surface activity of individuals include sex and reproductive condition, with reproductively active males traveling farther than female or males with regressed testes (Behrends et al. 1996a) and moonlight, with animals reducing surface activity and shifting activity toward places with relatively dense cover (Lockard and Owings 1974; Price et al. 1984). Daly et al. (1992b) found that D. merriami shifted from nocturnal activity during full moon to more crepusclar activity during dawn and dusk periods, suggesting a more complex and fine-grain compensatory behavioral response to moonlight rather than simply reducing overall surface activity to avoid moonlight.
Reproduction: The species D. merriami, and heteromyids in general, have relatively low reproductive output for rodents (see Wilson et al. 1985). In the wild, D. merriami and other kangaroo rat species typically breed one or two times per year, with the peak breeding being mid-winter through spring, although they may breed more frequently in good years (Duke 1944; Fitch 1948; Quay 1953; Pfieffer 1956; Holdenreid 1957; Reynolds 1960; Beatley 1969; Bradley and Mauer 1971, 1973; Kenagy 1973; Reichman and Van De Graaf 1973, 1975; Van De Graaff and Balda 1973; Flake 1974). Field observations of reproductive activity by D. merriami include several records of females producing successive litters at intervals of about two months, with a minimum interval of about 45-50 days (Daly et al. 1984). Breeding activities appear to vary in relation to ecological conditions, and individuals may not breed in years when conditions are poor. In good years, females are known to breed in their natal season (Daly et al. 1984). Studies indicate that nearly all adult individuals in a population are capable of breeding, but the proportion of individuals active at non-peak breeding periods (e.g., late summer-early fall) may be smaller (e.g., Kenagy 1973). Fall and winter rains, and the consequent production of herbaceous annuals, appears to be an important factor for breeding activities, but the positive effects do not always occur in the following season; i.e., there may be lag effects in the correlation between rainfall, production of herbaceous annuals, and kangaroo rat reproduction (e.g., Beatley 1969; Chew and Butterworth 1964). Herbaceous vegetation is ingested in greater quantities during the breeding season (Bradley and Mauer 1973; Reichman and Van De Graaff 1975), and there is experimental evidence that herbaceous material or free water is necessary for successful reproduction (Soholt 1977).
A captive breeding study of D. merriami by Daly et al. (1984) found that mean litter size for 129 deliveries of captive bred females was 2.4, with few litters exceeding four pups. Interestingly, 10 litters of wild-conceived litters averaged 3.7 pups. The modal gestation period for D. merriami in this study was 33 days. D. merriami do not have a post-partum estrus (i.e., receptive in conjunction with parturition), but they may become reproductively active within four days of removal of a nursing litter. Pups appear to stop nursing at about 25 days. The youngest mother in this captive breeding study conceived at 64 days of age and gave birth at 97 days. In the field, a female conceived her first litter between 40 and 50 days (Daly et al. 1984). D. merriami exhibit clear estrous cycles with a median length of 13.4 days and spontaneous ovulation (Wilson et al. 1985).
Based on field and laboratory studies of D. merriami, the maximal annual reproductive output of an individual female, based on a typical litter of two or three pups, is unlikely to exceed ten (Wilson et al. 1985), which is far below many other rodents that exhibit induced ovulation or post-partum estrous (e.g., murids).
Survival: Individual D. merriami have observed life spans of at least five years in the wild and at least seven years in captivity (Behrends, pers. obs.; Daly et al. 1990). However, the data on expected life span and annual survivorship of D. merriami in the field are equivocal because of the many practical limitations in measuring and interpreting survivorship (e.g., distinguishing between mortality and emmigration). Nonetheless, French et al. (1967) estimated a life expectancy for D. merriami of 4.3 months in the Mojave Desert. Chew and Butterworth (1964) observed 12-19 percent annual survivorship in a trapping study in the Mojave Desert, with most disappearances occurring from October to April and attributable to juvenile disappearances and the harsh winter. Zeng and Brown (1987), on the other hand, concluded that adult survivorship appears to be relatively high and year-to-year survivorship of males and females appears to be very similar. Because D. merriami are long-lived and recruitment of juveniles into populations probably varies from year-to-year, most populations are comprised primarily of adults. After correcting for emmigration, annual adult survivorship may be on the order of 75 percent (Brown and Harney 1993).
In a long-term study of predation of a D. merriami population in Palm Desert, California, Daly et al. (1990) recorded a total 50 known or presumed predations and found that more mobile individuals were at higher risk of predation, but general survivorship was not estimated because of the lack of control for emmigration. Important predators in the Daly study were coyotes, snakes, owls, and shrikes. Bobcats and foxes also would be expected to be important predators in western Riverside County.
Dispersal: Jones (1989) determined that D. merriami is philopatric; i.e., individuals tend to establish home ranges in proximity to their natal range. Dispersal in D. merriami is slightly male-biased, but more than 85 percent of individuals disperse less than 125 meters over their lifetimes (Jones 1989). Although recruitment of juveniles into the population is unknown, it probably varies in relation to breeding activities and ecological conditions (i.e., carrying capacity of the habitat). The data collected by French et al. (1967) and Chew and Butterworth (1964) suggests that juveniles are at high risk of disappearance, either through dispersal or mortality.
Socio-Spatial Behavior: Radio-telemetry studies and live-trapping studies of D. merriami have elucidated the basic patterns of this species' social and spatial behavior (e.g., Behrends et al. 1986a,b; Jones 1989). A review of heteromyid behavioral adaptations by Randall (1993) summarizes the fundamental aspects of D. merriami social organization. Although day burrows tend to be dispersed, this species exhibits overlapping home ranges. However, female-female overlap is less than male-male and male-female range overlap. Individuals primarily are solitary and asocial, although aggressive and non-aggressive interactions are not rare and individuals tend to tolerate familiar neighbors more than strangers. Core areas around day burrows may be aggressively defended. Although home ranges shift spatially over time, individuals tend to have long term associations with the same individuals. Average home ranges of males and females are similar in size, and range from 0.16 ha (0.4 acre) in Arizona to 2.6 ha (6.4 acres) in Texas, but individual home ranges may vary substantially (Behrends et al. 1986b).
The fact that kangaroo rats are relatively long-lived (> 7 years in captivity), exhibit conservative reproductive traits, juvenile mortality exceeds adult mortality (French et al. 1967; Zeng and Brown 1987) and that individuals disperse little between birth and adulthood (Jones 1989) all suggest that D. merriami have long-term stability in social communities.
Population densities of D. merriami can vary dramatically, probably in association with resource availability, but moderated by the conservative life history traits of the species; i.e., relatively low fecundity and recruitment of juveniles, storage of seeds, and effective predator avoidance. Geographically, typical population densities are variable and range from lows of 1 individual/ha in Texas to about 18 individuals/ha in Arizona (Behrends 1986b; Brown and Harney 1993). Typical densities in the Palm Desert area of California were approximately 6 individuals/ha over a five-year period (Behrends, pers. obs.). Subsequent trapping studies demonstrated an enormous range in abundance; fewer than 10 individuals were trapped on a 1-ha grid in drought years and more than 80 individuals in years following substantial rainfall and high production of food resources (Behrends, pers. obs.) (note that these are not density estimates for a unit area because the 1-hectare grid draws animals from beyond the grid). Reynolds (1958) conducted a 12-year trapping study in southern Arizona and recorded densities of 3.4 individuals/ha and high of 17.3 individuals/ha. Zeng and Brown (1987) recorded population densities ranging between about 2 and 18 individuals/ha in the Chihuahuan Desert in southeastern Arizona.
Community Relationships: The community ecology of heteromyid rodents, including kangaroo rats (Dipodomys spp.), pocket mice (Perognathus and Chaetodipus spp.) and and kangaroo mice (Microdipodops spp.) is among the most studied aspect of this family's biology. Brown and Harney (1993) provide a comprehensive overview and attempted synthesis of this complex subject. Presented here are some generalizations that fall from this large body of literature.
Arid grassland and desert environments support a surprising diversity of coexisting rodent granivores. The diversity and number of coexisting species varies depending on local conditions and the requirements of the constituent species. For example, the Aguanga kangaroo rat in Riverside County is known to overlap with two other kangaroo rats, (D. stephensi and D. simulans), possibly three pocket mice (Chaetodipus fallax, Chaetodipus californicus, and Perognathus longimembris), and at least four murids (Peromyscus maniculatus, P. eremicus, Neotoma lepida, and Reithrodontomys megalotis) that would compete for space and food resources. Brown and Harney (1993) conclude that "the composition of these assemblages is not random. Instead it is determined by interactions of the species with the physical environment, with other kinds of organisms, and with other rodent species." page 646. Generally, species that do coexist tend to occupy and exploit different microhabitats or niches or differ in their seasonality of resource exploitation. The trapping program conducted along Wilson Creek east of Sage in Riverside County, California recorded three species of kangaroo rats: D. merriami collinus, D. stephensi and D. simulans. D. merriami was trapped in coarse, sandy soils adjacent to the creek, D. stephensi was trapped in sparse grassland and along a dirt road away from the creek, and D. simulans was trapped in coastal sage scrub on the slopes above the creek (DUDEK 1995).
D. merriami exhibits somewhat greater habitat tolerance than other heteromyids. A survey of community assemblages by Brown and Harney (1993) found that D. merriami has one of the broadest geographic ranges and tends to be one of the most abundant species of assemblage where found.
Interspecific competition is an important component of the organization of heteromyid community structure. For example, competitive exclusion can result in nonrandom assemblages that partition the resources and habitats in the community. Other potential mechanisms of resource partitioning listed by Brown and Harney (1993) include habitat selection or restriction, independent adaptations, food partitioning and variable foraging efficiency, seed distribution, resource variability, predator-mediated coexistence, aggressive interference, and seasonality.
Kangaroo rats and other heteromyid rodents also modify their environments (Brown and Harney 1993). They dig burrows, which moves the soils and provides habitat and refugia for other species, including other rodents, reptiles, amphibians, birds and invertebrates. Collection, storage and consumption of seeds by kangaroo rats has profound effects on the vegetation structure of the habitats they occupy. For example, experiments by Brown and his colleagues in southeastern Arizona have demonstrated that kangaroo rats are a "keystone guild" where their removal from plots resulted in the habitat converting from desert shrub to grassland (Brown and Heske 1990). In addition, resource use by kangaroo rats substantially overlaps with that of seed-eating birds and harvester ants. Where kangaroo rats have been excluded in experimental plots, ants have increased dramatically (Brown and Harney 1993).
The coevolutionary results of such inter- and intraspecific community relationships and their relationship to plant communities are not understood, but it can be concluded that rodents area in important component of arid ecosystems. In addition to their direct impacts on plant communities, they are important prey for a variety of predators and their presence also affects populations of other prey such as small reptiles, lagomorphs and some birds (Brown and Harney 1993).
Physiological Ecology: Kangaroo rats and most other heteromyid species live in arid environments characterized by hot summers, long, cold winters, unpredictable precipitation, and ephemeral primary productivity of food sources (French 1993). For example, D. merriami have been observed on the surface at temperatures of -19 degrees Celsius (Kenagy 1993). Living in such extreme environmental conditions has high metabolic and thermoregulatory costs.
Kangaroo rats are perhaps most famous for their water conservation capabilities. Schmidt-Nielsen (1964) and French (1993) summarized the behavioral and physiological means by which kangaroo rats, and D. merriami, in particular, conserve water: they occupy burrows during daylight hours to avoid high temperatures; their evaporative water loss is much lower than other mammals when corrected for body mass; they have relatively low metabolic rates (about 30 percent lower than average mammals); they produce low volumes of highly concentrated urine and low moisture feces; and their water requirements can be satisfied by oxidative or metabolic water in conjunction with the seeds and herbaceous material they consume. D. merriami also produce highly concentrated milk, thus minimizing lactational water loss.
Energy conservation is very important for species living in extreme environments. D. merriami are active on the surface the entire year (e.g., Behrends et al. 1986b, Kenagy 1973). Other than at times of starvation, there is no evidence that D. merriami go into topor (a kind of hibernation) to conserve resources, as do pocket mice (Perognathus and Chaetodipus) and kangaroo mice (Microdipodops) (French 1993). However, D. merriami do tend to rest at temperatures at the lower end of thermal neutrality whenever possible to conserve energy (French 1993).
These physiological and behavioral characteristics allow kangaroo rats to inhabit a broad range of arid habitats in western North America, as well as allow individuals to survive during long periods of adverse climatic conditions.
Maintenance of suitable habitat will be important for this species. Aguanga kangaroo rats in Riverside Couny that occupy the habitat adjacent to Temecula and Wilson creeks probably experience fluctuations in habitat quality based on the fluvial processes related to flooding and drought. As with most kangaroo rat species, the Aguanga kangaroo rat probably is limited to habitats with sparse vegetation, as density of vegetation affects their burrowing, locomotion and foraging ability. The experimental removal of vegetation can result in an increase in kangaroo rats using the more open habitat (Rosenzweig 1973; Price 1978). Although the dynamics of vegetation change in the range of the Aguanga kangaroo rat have not been studied or described, maintaining natural fluvial processes along the creeks probably will be important. Any land uses that result in conversion of the scrub habitats to denser grasslands or other non-scrub coverage probably would have an adverse affect on the Aguanga kangaroo rat.
Habitat Loss: Although the Aguanga kangaroo is more widespread in eastern San Diego County and probably is not immediately threatened there, the Riverside population is much more restricted in distribution and occurs in an area subject to much greater human impact. Identified threats to the Aguanga kangaroo rat in Riverside County include loss of habitat, habitat fragmentation, sand mining, agricultural activities and grazing (S. Montgomery 1998). Off-road vehicles may also be a threat to this subspecies. Although the Aguanga kangaroo rat is associated with sandy washes and drainages, permanent habitat supporting sparse alluvial fan sage scrub often may not be in areas under the jurisdiction of the ACOE (i.e., within the ordinary high water mark of the drainage) or CDFG. For example, non-jurisdictional benches above creek channels probably are important for this species.
Genetic Isolation: Although there appears to be little genetic variation in kangaroo rats in general (Patton and Rogers 1993a,b), a study by Johnson and Selander (1971) suggested some degree of local genetic structure and the possibility inbreeding in a population D. merriami in Kramer, California. With such a small and potentially isolated population of the Aguanga kangaroo rat in Riverside County, such effects could have important conservation implications. Genetic studies of the Aguanga kangaroo rat are needed to compare the Riverside populations with the San Diego populations. In addition, studies in intervening locations between the known populations in the Aguanga, San Felipe, Earthquake and Mason valleys are needed; e.g., studies in the Warner Springs area.
Disease: The relationship of parasites and associates (e.g., viruses, bacteria, spirochetes, fungi, protozoa, etc.) in disease in D. merriami is not well understood, but various studies summarized by Whitaker et al. (1993) indicate that the species supports and/or may be affected by a variety of organisms. While many of these "parasites" may be benign, others may cause disease and mortality that could have severe impacts on small, insular populations. Because of the enormous number of parasites and associates found on D. merriami, only a brief summary of the general types and number of genera and species are reported here. The reader is directed to Whitaker et al. (1993) for a more detailed description.
D. merriami is known to carry at least two fungi species, eight species of protozoa, four species of tapeworm (cestodes), 10 species of roundworm (nematodes), 10 species of mites, 34 species of chiggers, two species hard ticks, two species of sucking lice, one moth, and 22 species of fleas. The effects of these parasites and their associates on the health of D. merriami generally are unknown. Many may be benign, but some may be pathogenic and have deleterous effects on populations (Whitaker et al. 1993). Such effects in small, isolated populations would be particularly serious. The relationships between host and parasites, such as whether they cause harm to the host, the geographic range of the parasites, and whether the number of parasites an individual carries is related to health, are all topics that require further study (Whitaker et al.1993).
Beatley, J.C. 1969. Dependence of desert rodents on winter annuals and precipitation. Ecology, 50:721-724.
Behrends, P., M. Daly, and M.I. Wilson. 1986a. Aboveground activity of Merriam's kangaroo rats (Dipodomys merriami) in relation to sex and reproduction. Behaviour, 96:210-226.
Behrends, P., M. Daly, and M.I Wilson. 1986b. Range use and spatial relationships of Merriam's kangaroo rats (Dipodomy merriami). Behaviour, 96:187-209.
Bradley, W.G. and R.A. Mauer. 1973. Rodents of a creosote bush community in southern Nevada. The Southwestern Naturalist, 17:333-344.
Bradley, W.G. and R.A. Mauer. 1971. Reproduction and food habits of Merriam's kangaroo rat (Dipodomys merriami). Journal of Mammalogy, 52:479-507.
Brown, J.H. and B.A. Harney. 1993. Population and community ecology of heteromyid rodents in temperate habitats. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 618-651.
Brown, J.H. and E.J. Heske. 1990. Mediation of a desert-grassland transition by a keystone rodent guild. Science, 250:1705-1707.
Chew, R.M. and Butterworth, B.B. 1964. Ecology of rodents in Indian Cove (Mojave Desert), Joshua Tree National Monument, California. Journal of Mammalogy, 45:203-225.
Daly, M., L.F. Jacobs, M.I. Wilson, and P.R. Behrends. 1992a. Scatter-hoarding by kangaroo rats Dipodomys merriami) and pilferage from their caches. Behavioral Ecology, 3:102-111.
Daly, M., P. R. Behrends, M.I. Wilson, and L.F. Jacobs. 1992b. Behavioral modulation of predation risk: moonlight avoidance and crepuscular compensation in a nocturnal desert rodent, Dipodomys merriami. Animal Behaviour, 44:1-9.
Daly, M., M. Wilson, P.R. Behrends, and L.F. Jacobs. 1990. Characteristics of kangaroorats, Dipodomys merriami, associated with differential predation risk. Animal Behavior, 40:380-389.
Daly, M., M.I. Wilson, and P. Behrends. 1984. Breeding of captive kangaroo rats, Dipodomys merriami and D. microps. Journal of Mammalogy, 65:338-341.
Dudek and Associates, Inc. (DUDEK). 1995. Stephens' kangaroo rat assessment for the Stardust Ranch/Mission Foundation Property.
Duke, K.L. 1944. The breeding season in two species of Dipodomys. Journal of Mammalogy, 25:155-160.
Fitch, H.J. 1948. Habits and economic relationships of the Tulare kangaroo rat. Journal of Mammalogy. 29:5-35.
Flake, L.D. 1974. Reproduction of four rodent species in a short grass prarie of Colorado. Journal of Mammalogy, 55:213-216.
French, A.R. 1993. Physiological ecology of the Heteromyidae: economics of energy and energy and water utilization. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 509-538.
French, N.R., B.G. Maza, and A.P. Aschwanden. 1967. Life spans of Dipodomys and Perognathus in the Mojave Desert. Journal of Mammalogy, 48:537-548.
Hall, E.R. 1981. The Mammals of North America, Second Edition, John Wiley and Sons, New York.
Holdenreid, R. 1957. Natural history of the bannertail kangaroo rat in New Mexico. Journal of Mammalogy, 38:330-350.
Johnson, W.E. and R.K. Selander. 1971. Protein variation and systematics in kangaroo rats (genus Dipodomys). Systematic Zoology, 20:377-405.
Jones, W. T. 1989. Dispersal distance and the range of nightly movements in Merriam's kangaroo rats. Journal of Mammalogy, 70:27-34.
Kenagy, G.J. 1973. Daily and seasonal patterns of activity and energetics in a heteromyid community. Ecology, 54:1201-1219.
Lidicker, W.Z., Jr. 1960. An analysis of intraspecific variation in the kangaroo rat Dipodomys merriami. University of California Publications in Zoology, 67:125-218.
Lockard, R.B. and D.H. Owings. 1974. Moon-related surface activity of bannertail (Dipodomys spectabilis) and Fresno (Dipodomys nitratoides) kangaroo rats. Animal Behaviour, 22:262-273.
Montgomery, S. 31 August 1998. Personal fax communication to the U.S. Fish and Wildlife Service.
Patton, J.L. and D.S. Rogers. 1993a. Cytogenics. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 236-258.
Patton, J.L. and D.S. Rogers. 1993b. Biochemical genetics. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 269-269.
Pfeiffer, E.W. 1956. Notes on reproduction in the kangaroo rat (Dipodomys). Journal of Mammaology, 37:449-450.
Price, M.V. 1978. The role of microhabitat in structuring desert rodent communities. Ecology, 59:910-921.
Price, M.V., N.M. Waser, and T.A. Bass. 1984. Effect of moonlight on microhabitat use by desert rodents. Journal of Mammalogy, 65:353-356.
Quay, D.B. 1953. Seasonal and sexual differences in the dorsal skin gland of the kangaroo rat (Dipodomys). Journal of Mammalogy, 34:1-14.
Randall, J.A. 1993. Behavioural adaptations of desert rodents (Heteromyidae). Animal Behaviour, 45:263-287.
Reichman, O.J. and M.V. Price. 1993. Ecological aspects of heteromyid foraging. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 539-574.
Reichman, O.J. and K.M. Van De Graaf. 1975. Association between ingestion of green vegetation and desert rodent reproduction. Journal of Mammalogy, 56:503-506.
Reichman, O.J. and K.M. Van De Graaf. 1973. Seasonal activity and reproduction patterns of five species of Sonoran Desert rodents. American Midland Naturalist, 90:118-126.
Reynolds, H.G. 1958. The ecology of the Merriam's kangaroo rat (Dipodomys merriami mearns) on grazing lands of southern Arizona. Ecological Monographs, 28:111-127.
Reynolds, H.G., 1960. Life history notes on Merriam's kangaroo rat in southern Arizona. Journal of Mammalogy, 41:48-58.
Rosenzweig, M.L. 1973. Habitat selection experiments with a pair of coexisting heteromyid rodent species. Ecology, 54:111-117.
Schmidt-Nielsen, K. 1964. Desert Animals, Oxford University Press, London, 277 pp.
Soholt, L.F. 1973. Consumption of herbaceous vegetation and water during reproduction and development of Merriam's kangaroo rat, Dipodomys merriami. American Midland Naturalist, 98:445-457.
Van De Graaff, K.M. and R.P. Balda. 1973. Importance of green vegetation for reproduction in the kangaroo rat. Journal of Mammalogy, 54:509-512.
Williams, D.F., H.H. Genoways, and J.K. Braun. 1993. Taxonomy. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 38-196.
Whitaker, J.O. Jr., W.J. Wrenn, and R.E. Lewis. 1993. Parasites. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 386-478.
Wilson, M., M. Daly, and P. Behrends. 1985. The estrous cycle of two species of kangaroo rats (Dipodomys microps and D. merriami). Journal of Mammalogy, 66:726-732.
Zeng, Z. and J.H. Brown. 1987. Population ecology of a desert rodent: Dipodomys merriami in the Chihuahuan Desert. Ecology, 68:1328-1340.
bobcat (Lynx rufus)
State: None
Federal: None
The bobcat is widespread throughout the Plan Area. This species requires large expanses of relatively undisturbed brushy and rocky habitats near springs or other perennial water sources. In addition to needing large habitat blocks, a key factor for conservation of the bobcat in the Plan Area is the provision of adequate dispersal and movement habitat, especially at potential bottleneck areas. Wildlife crossings of major roadways will need to be designed to accommodate bobcats. Use of key movement areas will need to be monitored to ensure that bobcats are safely using these areas.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 469,063 acres (57 percent) of suitable habitat in the Plan Area. Key conservation areas comprising large contiguous habitat blocks include the Santa Rosa Plateau-Santa Ana Mountains, Agua Tibia Wilderness-Palomar Mountains, Vail Lake-Wilson Valley-Aguanga, Anza-Cahuilla valleys, Badlands-San Jacinto Wildlife Area-Lake Perris, San Jacinto Mountains, Lake Mathews-Estelle Mountain, Lake Skinner-Diamond Valley Lake, and Santa Ana River-Prado Basin.
Include within the MSHCP Conservation Area habitat linkages and movement corridors between large Core Areas that allow dispersal and movement of bobcats throughout the Plan Area and to areas outside of the Plan Area. Key habitat connections and corridors include the following:
Within the MSHCP Conservation Area, maintain or improve functionality of dispersal routes. Existing undercrossings in key areas will be evaluated for their adequacy and improved as necessary to convey bobcats. Key crossings that will be evaluated include, but are not limited to, the following:
Conservation of the bobcat is primarily considered from a landscape perspective because the species is found throughout the Plan Area. However, there are definable large habitat areas and key movement and dispersal locations for focusing conservation efforts that will be important for conservation of this species in the Plan Area.
For the purpose of the conservation analysis, suitable habitat for the bobcat includes chaparral, coastal sage scrub, desert scrubs, grassland (annual, native, meadow, alkali playa), juniper woodland and scrub, Riversidean alluvial fan sage scrub, riparian habitats, woodlands and forests, and coniferous forests. Based on these habitats, the Plan Area support approximately 815,730 acres of suitable habitat for the bobcat. Table 1 shows the conservation of suitable habitat for the bobcat. Approximately 469,000 acres (57 percent) of suitable habitat would be in the MSHCP Conservation Area.
TABLE 1
SUMMARY OF HABITAT CONSERVATION - BOBCAT
| Within MSHCP Conservation Area | Outside MHSCP Conservation Area | ||||||
|---|---|---|---|---|---|---|---|
| Vegetation Type | Plan Area (Acres) |
Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
| Chaparral | 413,488 | 64,899 | 207,381 | 272,280 | 59,582 | 81,626 | 141,208 |
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,970 |
| Desert Scrubs | 9,378 | 3,675 | 1,314 | 4,989 | 44 | 4,345 | 4,389 |
| Grassland | 146,869 | 20,011 | 22,806 | 42,817 | 12,223 | 91,829 | 104,502 |
| Meadow | 492 | 0 | 87 | 87 | 18 | 387 | 405 |
| Playas and Vernal Pools | 7,914 | 3,828 | 2,923 | 6,751 | 0 | 1,163 | 1,163 |
| Juniper Woodland and Scrub | 1,082 | 336 | 274 | 609 | 23 | 450 | 473 |
| Riversidean Alluvial Fan Sage Scrub | 7,149 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,914 |
| Riparian | 14,607 | 3,920 | 7,173 | 11,193 | 368 | 3,045 | 3,413 |
| Coniferous Forest | 29,900 | 17 | 20,485 | 20,502 | 43 | 9,355 | 9,398 |
| Woodlands and Forest | 32,167 | 2,388 | 20,497 | 22,885 | 5,017 | 4,266 | 9,282 |
| TOTAL | 815,732 |
149,406 18% |
319,558 39% |
469,063 57% |
103,776 13% |
242,892 30% |
347,117 43% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
The MSHCP Conservation Area will preserve the remaining large, undisturbed areas of the Plan Area that provide adequate habitat for the bobcat, including sufficient area to support several home ranges (ranges vary widely from about 270 acres to 40,000 acres, but typically would be about 850 acres for males and 300 for females) and adequate prey (rabbits, squirrels, and other smaller rodents). Areas that probably would meet these minimum requirements include the Santa Rosa Plateau-Santa Ana Mountains, Agua Tibia Wilderness-Palomar Mountains, Lake Skinner-Diamond Valley Lake, Vail Lake-Sage-Aguanga, Anza Valley, San Jacinto Mountains, the Badlands-Lake Perris-San Jacinto Wildlife Area, Lake Mathews-Estelle Mountain, and the Santa Ana River-Prado Basin. Bobcats are likely to occur in other areas of the reserve, such as Sedco Hills-Kabian Park, Warm Springs Creek, Lakeview Mountains, and the Jurupa Mountains, but these areas provide limited area for bobcats and may be mortality sinks because of the existing and planned roads and human presence.
As described below under Data Characterization, 34 of the 75 point localities have a precision of "1" or "2." Of these 34 point localities, 12 (35 percent) would be inside the MSHCP Conservation Area. The abundance and distribution of data points for this species may be misleading due to lack of reporting for a species that is considered "common."
Habitat linkages between the large habitat blocks described above will be important for accommodating movement and dispersal. Bobcats make daily movements of approximately 0.6 mile to 6.2 miles per day (Larivière and Walton 1997), but most of these movements will be within the large habitat blocks related to foraging. The critical reserve configuration issue is whether habitat linkages will allow successful dispersal between large habitat blocks by yearlings. While young are capable of dispersing long distances (at least 182 km [113 miles]), they require sufficient cover to move safely. Dispersal connections through marginal habitat should be as short as possible. Movements that could be made within one night could occur across marginal habitats, but longer movements will require refugia for resting, such as rockpiles, brushpiles, windfalls, hollow snags, and hollow trees. Riparian habitat and dense and rocky chaparral or coastal sage scrub along longer movement corridors (e.g., longer than six miles) would be ideal. In addition, movement across freeways and major roads will require adequate overpasses or underpasses to reduce the chance of mortality from vehicle collisions. Open bridges that span the flood plain are the preferred undercrossing. Culverts should be at least 10-20 feet wide to accommodate movement, with fencing and vegetative cover to funnel bobcats into the wildlife crossing.
The key bobcat movement linkages between Core Areas are as follows:
In summary, conservation for the bobcat will be achieved by inclusion of at least 469,000 acres of suitable Conserved Habitat. Although the current population of the bobcat in the Plan Area is unknown, it is assumed to be widespread in suitable habitat. Currently its distribution in the Plan Area is likely more constrained by limited habitat connections than from too little habitat. Large connected habitat blocks in the MSHCP Conservation Area will provide for movement areas that are adequate to support the life history needs of the bobcat, including foraging, reproduction, and dispersal activities. The main habitat areas for bobcats in the MSHCP Conservation Area include the Santa Ana Mountains-Santa Rosa Plateau, the Agua Tibia Wilderness-Palomar Mountains, the San Jacinto Mountains and Foothills, Lake Mathews-Estelle Mountain, Lake Skinner-Diamond Valley Lake, the Badlands, Santa Ana River-Prado Basin, and the foothills of the San Bernardino Mountains.
About 347,000 acres (43 percent) of suitable habitat for the bobcat would be outside the MSHCP Conservation Area. Lands outside the MSHCP Conservation Area tend to be in areas that currently are more fragmented by urban and agricultural development and thus less suitable for long-term conservation of the bobcat.
The MSHCP database includes 75 records for the bobcat. Of the 75 records, 24 (32 percent) are precision code "1" (an "x' and "y" coordinate that allows for good precision in the location), 10 (13 percent) are precision code "2" (one "x" or "y" coordinate or equivalent), and the remaining 41 (55 percent) are precision codes "3" or "4" (relatively imprecise locations from general areas). Most of the records are relatively recent, with 55 (73 percent) since 1990. Most of the others are from the 1970s and 1980s, with only two of the records dating from 1908 and 1916, respectively, and two others with no date provided for the records. Data records for the bobcat are scattered throughout the Plan Area, with clusters on the Santa Rosa Plateau, Lake Skinner-Diamond Valley Lake area, and the Banning-Beaumont area. These scattered data points represent records since 1990. Based on the recency of the much of the data and the scatter of records throughout the Plan Area, the database appears to provide a fairly good representation of the population distribution of this species in the Plan Area.
Although widespread throughout Riverside County, the bobcat is most closely associated with rocky and brushy areas near springs or other perennial water sources, primarily in foothills comprised of chaparral habitats. Bobcats prefer areas with adequate cover in the form of rock cavities, snags, stumps and dense brush (Zeiner et al. 1990), but they occur in any sizable area of relatively undisturbed scrub habitat (S. Montgomery 1998). Habitat preferences of the bobcat throughout the year strongly reflect prey abundance (see Larivière and Walton 1997).
Of the 75 records in the MSHCP database, 17 (23 percent) are in chaparral, 12 (16 percent) are in scrub (Riversidean sage scrub, Diegan coastal sage scrub, desert succulent scrub, and disturbed alluvial), 16 (21 percent) are in grassland (including annual and non-native grassland and alkali playa), and seven (9 percent) are in oak woodland, coniferous forest, and riparian habitats. Twenty-two records (29 percent) are in areas currently mapped as agriculture (orchards, field croplands and dairy) and residential/urban/exotic. These records may or may not be valid, but the occasional sightings of bobcats in such areas would not be unusual, especially if the areas are near natural habitats. In addition, there will be a bias for sightings in areas where people are more likely to see them.
Bobcats occur throughout the contiguous United States, Mexico south to Rio Mescale, and Canada, except for Vancouver Island, Prince Edward Island, and Newfoundland (Hall 1981; Larivière and Walton 1997). The subspecies L. r. californicus occurs throughout California, with the exception of the extreme northwestern portion of the state and the Great Basin, Mojave, and Colorado deserts. Marginal records for this subspecies are Mt. Shasta, Lee Vining Creek Grade, Riverside, San Jacinto Mountains, and Santa Rosa Mountains (Hall 1981).
Bobcats occur throughout western Riverside County in suitable habitat. Areas with frequent observations include the Santa Rosa Plateau, the Lake Skinner-Diamond Valley Lake area, the Badlands, Banning-Beaumont, Lake Mathews, Santa Ana River, and Sage.
Key areas for the bobcat are areas that still support large tracts of relatively undisturbed habitat such as the Santa Rosa Plateau and adjacent Cleveland National Forest in the Santa Ana Mountains, Lake Skinner-Diamond Valley Lake, Lake Mathews-Estelle Mountain, the Badlands, Santa Ana River, Vail Lake, Sage, Aguanga, Anza Valley, Agua Tibia Wilderness-Palomar Range, and the San Jacinto Mountains.
Population and life history traits of bobcats appear to vary geographically (e.g., Larivière and Walton 1997; Rucker et al. 1985), therefore the information provided here must be viewed with caution. Generalizations of characteristics from other populations may only roughly approximate those of the bobcat population in the MSHCP Plan Area.
Genetics: Little genetic information is available for the bobcat. The diploid number of chromosomes of the bobcat is 38 (Larivière and Walton 1997). They are known to hybridize with feral cats (Felis cattus) (Larivière and Walton 1997).
Diet and Foraging: Bobcats are primarily carnivores (Larivière and Walton 1997). In most regions their main diet is lagomorphs (rabbits and hares), with sciurids (squirrels) and microtine rodents consumed opportunistically. However, bobcat diets also appear to reflect the availability of prey. For example, in central Arizona woodrats (Neotoma spp.) and heteromyids (kangaroo rats [Dipodomys spp.] and pocket mice [Perognathus and Chaetodipus spp.]) made up the majority of bobcat diets, with lagomorphs making up a smaller proportion (Jones and Smith 1979). Other prey include muskrats (Ondatra zibethicus), woodchucks (Marmota monax), porcupines (Erethizon dorsatum), beavers (Castor canadensis), and mountain beavers (Aplodontia rufa). Bobcats occasionally kill domestic animals. They are a major predator of the federally-listed endangered and state-listed threatened San Joaquin Valley kitfox (Vulpes macrotis). Larger prey include mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), American pronghorn antelope (Antilocarpa americana), and bighorn sheep (Ovis canadensis). Bobcats also prey on a variety of birds, reptiles, fish, and insects.
Bobcats are solitary hunters. They typically hunt in areas with cover using a stealth approach and then pouncing and striking. However, they may also sit and wait along game trails. Kills may be cached but not fully consumed.
Daily Activities: Bobcats mostly are nocturnal, but may be active any time of the day. Their peak activities generally are 1800 to 2400 hrs in the evening and 0400 to 1000 in the early to mid-morning (Larivière and Walton 1997). Their lowest period of activity is midday. Resting sites include steep-sloped, rocky areas with dense vertical cover and sparse herbaceous ground cover, rockpiles, brushpiles, windfalls, hollow snags, and hollow trees. Bobcats often rest near fresh kills. Daily movements range from approximately 1 km (0.6 mile) to 10 km (6.2 miles) per day (Larivière and Walton 1997).
Reproduction: Breeding is polygamous (both sexes may have several partners) and females are polyestrous (multiple estrous periods during a breeding season) (Larivière and Walton 1997). Females that fail to become pregnant in the early spring may become estrous again in late spring or summer and pregnancy rates appear to be affected by environmental factors. Females are induced ovulators, meaning that copulation stimulates ovulation as opposed to spontaneous ovulation. The peak of the breeding season typically is December to July, but timing varies with latitude, longitude, altitude and climate. Kittens may be born any month of the year, but peak births occur from April to June. The typical gestation period is about 63 days and litter sizes range from 1-6, but vary geographically. For example, the mean litter size in a Kansas population is 2.0, while in Utah the mean litter size is 3.5. Females may become estrous in their natal year, but most first pregnancies occur in the second year. In a study of bobcats in Oklahoma, pregnancy rates in yearlings was 46 percent compared to 92 percent for adults (Rolley 19885). Litters of adults tend to be larger than those of yearlings.
Male reproduction is variable and more related to body weight than to age. However, adult males may have less reduction in sperm production in the late summer and fall after the breeding season than younger males. Adult males also are reproductively active until death.
Survival: Bobcats may live up to 32 years in captivity. Mortality in the wild is strongly related to harvesting of bobcats through hunting, trapping, and poaching (Larivière and Walton 1997). In the past, the bobcat has been considered a "varmint" species and was often trapped or hunted by ranchers and farmers (Nowak 1991). In states and Canadian provinces where bobcats are harvested, annual survival rates range from 0.19 in Massachusetts under heavy harvesting (Larivière and Walton 1997) to 0.66 for adults and 0.3 for juveniles in Oklahoma (Rolley 1985). Bobcats also die from disease and infections (e.g., from porcupine quills), road kills (Larivière and Walton 1997), and occasional electrocution from power lines (Williams 1990). In California, where bobcats are not harvested, 35 percent of mortality was due to predation, 15 percent due to disease, and 10 percent due to starvation (Larivière and Walton 1997). Based on a study of a harvested population in Oklahoma, Rolley (1985) suggested that natural mortality rates in the absence of harvest probably are quite low. He also suggests that harvesting may differentially affect age groups (i.e., juveniles, yearlings, and adults), with relatively more effects on older animals. The consequence of these differential effects on the population age structure and productivity is unknown, but biased harvesting of more productive adult males and females could reduce population growth rates and jeopardize persistence.
Dispersal: Young bobcats start traveling alone by six months of age, but stay close to their natal den. Yearlings permanently disperse before the next litter is born and are capable of moving very long distances. For example, two young males dispersed 182 and 158 km, respectively (Larivière and Walton 1997).
Socio-Spatial Behavior: Home ranges and population densities vary geographically, and in relation sex and resources. Larivière and Walton (1997) reported home ranges of 1.1 to 158 sq. km, with male home ranges consistently larger than female ranges. Bradley and Fagre (1988) reported male home ranges of 3.5 sq. km for males and 1.2 sq. km for females in an area of fairly high bobcat density in south Texas. Typically, males ranges are about three times larger than female ranges. Male ranges overlap the ranges of both other males and females, but female ranges generally are exclusive of other females. Bobcats show high site fidelity between seasons and range boundaries are maintained by visual and olfactory cues, including scent marking with feces, urine, anal glands, and scrapes. Changes in home ranges usually only occur after the death of the resident animal.
Home range sizes track food availability; as prey decrease, home ranges increase in size. Home ranges also vary in relation to breeding activities. Male ranges increase during the breeding season, while female ranges are smallest during the breeding and rearing season. However, for females at least, breeding and rearing probably coincides with greater prey availability, so it is difficult to determine whether the decrease in home range size is due to breeding activities or better foraging opportunities. For males, the relationship seems clearer; male ranges increase during breeding, presumably to seek out and consort with females, even when prey availability presumably is higher.
Population density ranges reported by Larivière and Walton include one bobcat per 3.6 to 4.1 sq. km in Arizona, one per 0.7 to 0.9 sq. km in California, one per 11 sq. km in Oklahoma, and one per 23.3 sq. km in Utah. Relatively high densities for the bobcat are reported from south Texas; 1.0-1.3 bobcats per sq. km (Bradley and Fagre 1988). Population densities appear to fluctuate in response to prey, so these density values should be viewed as approximations. However, in general prey densities are lower in arid and semi-arid environments.
Community Relationships: As a top predator, the bobcat, in conjunction with coyotes (Canis latrans), mountain lions (Puma concolor), foxes (Vulpia spp.), and raptors, may have a significant impact on populations of prey species such as lagomorphs and rodents. This predation on herbivores and granivores may in turn affect vegetation conditions.
Bobcats overlap with both coyotes and mountain lions, and their habitats and diets are very similar to that of the coyote. It is expected that such resource overlap would result in behavioral mechanisms that partition resources and allow coexistence of the species. Koehler and Hornocker (1991) examined seasonal use of habitats and prey in central Idaho by mountain lions, bobcats, and coyotes to determine how they coexist. They found partitioning of prey and habitat resources in the summer, with bobcats and mountain lions foraging in areas with cover for stalking, while coyotes tended to use open areas (i.e., coursing). During the winter bobcats specialized on voles while lions hunted for elk (Cervus elaphus) and deer. Physically, the larger lion is able to negotiate deep snow better, while the lighter bobcat utilized snow free south-southwest exposures at lower elevations. Coyotes overlapped with both felid species during the winter, hunting and scavenging ungulates and foraging in open areas for smaller prey. During the winter there was more overlap in resource use and direct or "interference" competition was more common. While coyote kills were not visited by bobcats or lions (possibly because of pack formation), about one-half of bobcat kills were visited by coyotes and lions. During the winter lions killed both bobcats and coyotes while defending or usurping food caches, with five of eight deaths of bobcats attributed to mountain lions. The killing apparently was related to competition for kills because the bobcats were not consumed by the lions. In south Texas, on the other hand, Bradley and Fagre (1988) observed no obvious spatial or temporal habitat partitioning between coyotes and bobcats.
Physiological Ecology: Bobcats do not appear to have specific metabolic adaptations to geographically different or seasonally changing environmental conditions. They occur in widely varying geographical locations (longitudinally, latitudinally, and altitudinally) throughout the contiguous United States, southern Canada, and south to Rio Mescale, Mexico. Their metabolic rate does not vary seasonally, but rather they use behavioral mechanisms such as sunning and selection of microhabitats for the added energy requirements in the winter (Larivière and Walton 1997). In winter, bobcats also appear to use lower habitats to avoid snow (Larivière and Walton 1997).
Habitat Loss and Fragmentation: Loss of large, relatively undisturbed blocks of habitat and adequate linkages between blocks of habitat are a serious threat to the persistence of bobcats in western Riverside County. Disturbance from human recreation such as hiking, mountain biking, off-road vehicles and mortality from vehicle collisions probably will cause the gradual disappearance of bobcats from the more urbanized areas in the County.
Disease: Bobcats are known to carry several diseases, including rabies and cat-scratch fever, gastric enteritis, respiratory infections, and Cyauxzoon felis transmitted by the tick Dermacentor variabilis. They are also host to various trematodes, cestodes, nematodes, protozoa, acanthocephlans, helminths, and Microfilariae. Ectoparasites found on bobcats include mites (Notoedres cati), ticks, and lice (Felicola subrostratus).
In general, bobcats are very adaptable and flexible in their habitat and prey requirements. However, maintenance of undisturbed habitat patches for breeding, preferably with rock outcrops and boulders, is important for conserving and managing this species. A key factor for the bobcat will be conservation of movement and dispersal habitat linkages along major drainages and accommodation of movement under or over major roadways via drainage culverts and specific wildlife crossings (e.g., wildlife overpasses). Bobcats are highly susceptible to collisions with vehicles. Crossings used by mule deer will be sufficient for bobcats; e.g., culverts measuring 10-20 feet in width and providing for unobstructed visual contact from end to end. In addition, fencing along roadways near movement linkages to funnel bobcats into the wildlife crossing and reduce vehicular collisions should be used.
A radiotelemetry study of bobcats by Bradley and Fagre (1988) provides some relevant observations for management of the species. Their study was on a 1,093-hectare (2,700 acres) range management research site in south Texas. The research site supports dense thickets, open savannahs, and native grassland, as well as fencelines, roads, grazing pasture, hay pasture and some buildings. The study found that bobcats used fencelines and roads within their home ranges for hunting more than expected by chance. They exhibited a slight avoidance of cattle, but were relatively undisturbed by human presence. This study suggests that bobcats can coexist successfully with humans as long as the human activities do not reduce habitat and prey resources or increase mortality rates (i.e., harvesting or vehicular collisions).
Bradley, L.C. and D.B. Fagre. 1988. Coyote and bobcat responses to integrated ranch management practices in south Texas. Journal of Range Management 41:322-327.
Crooks, K. and D. Jones. 1998. Monitoring program for carnivore corridor use in The Nature Reserve of Orange County. Annual Report - 1998. Prepared for The Nature Reserve of Orange County, 24 pp + appendices.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Jones, J.H. and N.S. Smith. 1979. Bobcat density and prey selection in central Arizona. Journal of Wildlife Management 43:666-672.
Koehler, G.M. and M.G. Hornocker. 1991. Seasonal resource use among mountain lions, bobcats, and coyotes. Journal of Mammalogy 72:391-396.
Larivière, S. and L.R. Walton. 1997. Lynx rufus. In Mammalian Species No. 564:1-8. Published by the American Society of Mammalogists.
Montgomery, S. 31 August 1998 & 28 September 1998. Personal fax communication to the U.S. Fish and Wildlife Service.
Nowak, R.M. 1991. Walker's Mammals of the World, Fifth Edition. The Johns Hopkins University Press, Baltimore, Vol I & II, 1,629 pp.
Rolley, R.E. 1985. Dynamics of a harvested bobcat population in Oklahoma. Journal of Wildlife Management 49:283-292.
Rucker, R.A., M.L. Kennedy, G.A. Heidt, and M.J. Harvey. 1989. Population density, movements, and habitat use of bobcats in Arkansas. The Southwestern Naturalist 34:101-108.
Williams, R.D. 1990. Bobcat electrocution on powerlines. California Fish and Game Notes, 187-189.
Zeiner, D.C., W.F. Laudenslayer, Jr., K.E. Mayer, and M. White. 1990. California Wildlife, Volume III, Mammals. California Statewide Wildlife Habitat Relationships System. Department of Fish and Game, Sacramento, California.
brush rabbit (Sylvilagus bachmani)
State: None
Federal: None
The brush rabbit occurs throughout the Plan Area in suitable habitat, including chaparral, coastal sage scrub (Diegan coastal sage scrub, Riversidean sage scrub, and alluvial fan sage scrub), riparian and woodland habitats, coniferous forest, and agricultural areas (grove/orchard, and field crops). They occur at all elevations up to 6,000 feet. Geographical areas with apparent concentrations of observations include Sage, Anza Valley, Santa Rosa Plateau, and the foothills of the San Jacinto Mountains. The brush rabbit population size in the Plan Area is unknown. Although relatively little is known of this species in the Plan Area, with a large enough MSHCP Conservation Area, specific management regimes will not be necessary. All that appears to be necessary for conservation of the brush rabbit are large habitat areas, adequate vegetative cover, and suitable dispersal and/or movement linkages.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 382,115 acres (63 percent) of suitable habitat in the Plan Area. Conservation in the primary core habitat areas includes the Existing Core A (10,740 acres), Existing Core B (71,490 acres contiguous with Cleveland National Forest in Orange County), Existing Core C (15,610 acres), Existing Core F (8,360 acres), Existing Core G (4,490 acres), Existing Core H (17,470 acres), Existing Core I (9,610 acres contiguous with San Bernardino National Forest in San Bernardino County), Existing Core J (24,370 acres), Existing Core K (149,750 acres), Existing Core L (24,750 acres contiguous with Cleveland National Forest in San Diego County), Existing Core M (10,460 acres contiguous with Cleveland National Forest in San Diego County), Proposed Core 1 (7,470 acres), Proposed Core 2 (5,050 acres), Proposed Core 3 (24,920 acres), Proposed Core 4 (11,890 acres), Proposed Core 5 (3,220 acres), Proposed Core 6 (4,290 acres), and Proposed Core 7 (50,000 acres).
Include within the MSHCP Conservation Area 44,000 acres of dispersal and/or movement linkages between large blocks of conserved habitat.
For the purpose of the conservation analysis, suitable habitat for the brush rabbit includes chaparral, coastal sage scrub (Diegan coastal sage scrub, Riversidean sage scrub), Riversidean alluvial fan sage scrub and woodland and forest. Despite a substantial percentage of observations in areas mapped as grassland, it is not included as a suitable habitat in the analysis because this species typically is observed at the shrub-grassland ecotone and not in open grassland habitats (e.g., Connell 1954; Chapman 1971). Therefore, including grassland as a suitable habitat may result in a gross overestimate of the suitable habitat conserved. On the other hand, because brush rabbits do occur at least along the edges of grasslands, the conservation estimate probably is conservative. Based on these assumptions about suitable habitat, the Plan Area supports approximately 605,490 acres of suitable habitat. Table 1 shows the conservation suitable habitat for the brush rabbit. Approximately 382,115 acres (63 percent) of the existing suitable habitat would be in the MSHCP Conservation Area.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
BRUSH RABBIT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 413,488 | 64,899 | 207,381 | 272,280 | 59,582 | 81,626 | 141,208 |
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,790 |
| Riversidean Alluvial Fan Sage Scrub | 7,149 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,914 |
| Woodlands and Forest | 32,167 | 2,388 | 20,497 | 22,885 | 5,017 | 4,266 | 9,283 |
| TOTAL | 605,490 | 117,619 (19%) |
264,496 (44%) |
382,115 (63%) |
91,057 (15%) |
132,318 (22%) |
223,195 (37%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described below under Data Characterization, 65 of the 122 point localities have a precision of "1" or "2." Of these 65 point localities, 15 (23percent) would be inside the MSHCP Conservation Area. However, this relatively low percentage of observed locations in the reserve does not reflect the large proportion of suitable habitat that will be conserved.
The brush rabbit will benefit from new conservation of approximately 382,000 acres of suitable habitat within the MSHCP Conservation Area. A substantial amount of habitat conservation will be within large blocks of habitat in areas known to support populations of brush rabbit, including the Santa Rosa Plateau, Lake Skinner, Sage-Wilson Creek, and Tule Creek-Anza Valley, and other areas with high potential to support the species, including the Santa Ana Mountains, Agua Tibia Wilderness-Palomar Range, San Jacinto Mountains, and the foothills of the San Bernardino Mountains. Acreage within the core habitat areas are summarized in Objective 1.
Conservation of the brush rabbit will depend on preserving large blocks of suitable habitat capable of sustaining viable populations of the rabbit. Habitat linkages between distant large habitat blocks may be important for this species. Brush rabbits appear to be sedentary compared to other Sylvilagus species and other mammals, although little specific dispersal data are available (e.g., see Chapman 1971). Because brush rabbits are unlikely to disperse through unsuitable habitat, linkages between large habitat blocks would have to contain habitat suitable for permanent occupation. As such, there probably will be distinct populations of brush rabbits that have little, if any, interchange of individuals in the future. For example, the Santa Rosa Plateau-Santa Ana Mountains population may be reproductively isolated from the population in the Lake Mathews-Estelle Mountain area because of Interstate 15 and lack of contiguous suitable habitat connections between the two areas. It is unknown whether brush rabbits use the crossings under Interstate 15 at Indian and Horsethief canyons. It also is unclear whether populations in the Santa Rosa Plateau will be isolated from the Agua Tibia Wilderness-Palomar Mountains population because of Interstate 15. Pechanga Creek currently may or may not provide suitable habitat for movement between the two areas. Highway 79 along Temecula Creek may be a barrier to north-south dispersal between the Vail Lake-Sage area and Agua Tibia-Palomar Range, although individuals may use culverts along some of the drainages such as Kolb Creek and Arroyo Seco. The Santa Ana River-Prado Basin population probably is isolated from other populations in the Plan Area, but should be linked with populations in Orange County along the river and in the Chino Hills. As summarized in Objective 2, approximately 44,000 acres will be conserved in habitat linkages, but not all of this habitat is likely to be suitable for the brush rabbit.
In summary, conservation for the brush rabbit will be achieved by inclusion of approximately 382,000 acres of suitable Conserved Habitat in the MSHCP Conservation Area. In addition, large habitat blocks throughout the Plan Area with interconnecting linkages will be conserved, including the Santa Ana River-Prado Basin, Santa Rosa Plateau-Santa Ana Mountains, Agua Tibia Wilderness-Palomar Mountains, San Jacinto Mountains and foothills, Lake Skinner-Diamond Valley Lake, Sage-Vail Lake-Wilson Valley, and the Anza and Tule valleys. The Santa Ana River-Prado Basin and Santa Rosa Plateau-Santa Ana Mountains may be functionally isolated from the other habitat areas by the Riverside Freeway (State Highway 91) and Interstate 15, but they are large enough habitat areas (including portions in Orange and San Diego counties) to sustain viable populations. The other habitat blocks are reasonably well connected and rabbits should be able to disperse throughout these areas.
Approximately 223,195 acres (37 percent) of suitable habitat for the brush rabbit will not be conserved. Suitable habitat outside the MSHCP Conservation Area tends to be in areas that are more fragmented by urban and agricultural development and less suitable for the long-term conservation of the brush rabbit.
The MSHCP database includes a total of 122 records for the brush rabbit. Of the 122 records, 57 (47 percent) are precision 1 (i.e., an "x" and "y" coordinate that allows for a relatively precise location), eight (6 percent) are precision 2 (one "x" or "y" coordinate or equivalent that allows a reasonably precise location) and the remaining 57 (47 percent) are precision codes 3 and 4 that do not allow for a precise location of the record. Most of the records are recent, with 102 (84 percent) since 1990. The primary concern about the data is the accuracy of field identification between the brush rabbit and the co-occurring desert cottontail (Sylvilagus audubonii), which occurs in more xeric conditions, is somewhat larger (0.6-1.2 kg versus 0.6-0.8 kg), lighter in color and has longer ears (76-102 mm in length versus 51-66 mm). The desert cottontail is more common in arid valleys, but there may be a tendency to identify the two species in the field by habitat association, attributing brush rabbits to areas with heavier brush.
Brush rabbits inhabit dense, brushy cover, most commonly in chaparral vegetation (Chapman 1974). They also occur in early successional stages of oak and conifer habitats (Zeiner et al. 1990). Brush rabbits do not dig their own dens, but use the burrows of other species, brush piles, or "forms." In the San Francisco Bay area, Connell (1954) found that brush rabbits concentrate their activities at the edge of brush and exhibit much less use of grass areas. Use of interior brush also was used irregularly and Connell suggests that the brush-herb ecotone is better habitat than continuous chaparral. Chapman (1971) also found that brush rabbits at a study site near Corvallis, Oregon rarely left brushy cover. Brush may be used more in the drier seasons while grasses are used in the wetter seasons in relation to growth of annual herbaceous vegetation. Use of habitat also probably is related to the breeding season.
Within the MSHCP Plan Area, 45 (37 percent) of the occurrences are in chaparral (chaparral, red shank chaparral), 13 (11percent) in coastal sage scrub (Diegan coastal sage scrub, Riversidean sage scrub, disturbed alluvial), one (<1 percent) in desert scrub, 25 (20 percent) in non-native grassland (possible confusion with the desert cottontail?), four (3 percent) in oak woodland (coast live oak woodland and Engelmann oak woodland), two (1.6 percent) in coniferous forest, 12 (10 percent) in agriculture (grove/orchards, field croplands), and 19 (15 percent) in urban/residential/exotic landscapes. One location was mapped in open water/reservoir, but this probably is a mapping or registration error.
The brush rabbit, S. bachmani, is a Pacific coastal species that occurs west of the Cascades and Sierra Nevadas from southern Oregon to Baja California, Mexico. It is generally absent from the dry Central Valley, except for a small population of S. b. riparius known only from the west side of the San Joaquin River in Stanislaus County. Marginal records for the subspecies S. b. cinerascens include San Emigdio Canyon; Reche Canyon; Dos Palmas Springs; Santa Rosa Mountains; and Baja California (Hall 1981). They occur from sea level to at least 2,070 meters (6,800 feet) (Chapman 1974).
The brush rabbit occurs in appropriate habitat throughout western Riverside County. Populations appear to be centered around Sage, Anza Valley, Santa Rosa Plateau, and the foothills of the San Jacinto Mountains. Additional localities include Santa Ana River, Alberhill, Vail Lake, Lakeview Mountains, the Badlands, Sycamore Canyon, Banning-Beaumont, Calimesa, and Garner Valley.
Santa Rosa Plateau and Sage area, but occurs throughout the Plan Area in appropriate habitat.
Genetics: The brush rabbit has a diploid chromosome number of 48 (Chapman 1974). No other relevant genetic studies were found.
Diet and Foraging: Brush rabbits are herbivorous and graze on a wide variety of grasses and annual forbs, including clovers (Trifolium spp.), foxtail barley (Hordeum murinum), bromes (Bromus spp.), wild oats (Avena spp.), and thistles (Sonchus asper, Circium lanceolatum) (Chapman 1974; Zeiner et al. 1990). They prefer the newly grown tips of plants (Chapman 1974). Brush rabbits also feed on species such as creeping eragrostis (Eragrostis hypnoides), spikerush (Eleocharis palustris), wild rose (Rosa californica), Mexican tea (Chenopodium ambrosoides), marsh baccharis (Baccharis douglasii), rush (Juncus spp.), the roots of poison hemlock (Conium maculatum), and the stems and leaves of California blackberry (Rubus ursinus) (Chapman 1974). Their diet and foraging behavior vary in relation to season; they forage on annual, herbaceous vegetation during the wetter season and perennial brush species during the drier season.
Daily Activities: Brush rabbits mostly are crepuscular, with activity greatest around dusk and dawn. They are less active at night and occasionally active during the day (Zeiner et al. 1990). They often stay just inside brushy cover and then venture into open grassy areas to feed (Connell 1954; Chapman 1974). They spend a considerable time sunning, usually following rain or fog (Chapman 1974). Connell (1954) found that males made their greatest daily moves February to March, while females' longest moves were December to February. Average daily moves were 81+15 feet by males and 61+10 feet by females.
Reproduction: The peak breeding season for brush rabbits in California is from December to May and possibly into June (Chapman 1974). However, based on an analysis of reproductive organs from rabbits taken in San Francisco Bay area, Mossman (1955) determined that males are capable of breeding from possibly October through July and most likely from November through June. He concluded that males probably are not fertile from July through October, the driest part of the year. Females exhibit pregnancy from the first week of December until about the end of June (Mossman 1955). In Oregon, the breeding season is the same length, but runs from about February to August (Chapman and Harman 1972). Gestation is 27+3 days. Three and possibly four litters of 2-5 offspring are produced annually (Chapman and Harman 1972; Mossman 1955) and an annual production of 15.2 young per female was calculated by Chapman and Harman (1972). Chapman and Harman conclude that brush rabbits are not as fecund as some other cottontail species that may produce up to 35 offspring per year. Litter sizes are smaller in Oregon than California and there appears to be a negative correlation between litter size and latitude and a positive correlation between breeding and the rainy season (Chapman and Harman 1972). In Oregon brush rabbits, it was determined that 16.3 percent of ova failed to implant and 15.5 percent of embryos were resorbed (Chapman and Harman 1972). Based on intervals between litters, females exhibit a postpartum estrus and can become pregnant shortly after giving birth (Chapman and Harman 1972).
Brush rabbits prepare a nest cavity approximately 75 by 150 mm lined with fur and small amounts of grass (Chapman 1974). The young are only fed at night and spend about two weeks in the nest. They mature in about four to five months, but females at least probably do not breed in their natal season (Chapman and Harman 1972; Mossman 1955).
Survival: Annual survival rates in brush rabbits are relatively low, but appear to be age-related. Based on live-trapping, Connell (1954) estimated an annual survival rate of males and females combined of only 15 percent over 12 months. He concluded that mortality or emigration (these two causes of disappearance could not be separated in the field study) of young-of-the-year accounted much for much of the "mortality" in the population, with males disappearing at a higher rate in the first six months after first capture (86percent) compared to females (67percent). In contrast, only two of seven (29 percent) of adults trapped in April and May were not retrapped in September. The longest-lived brush rabbits in the wild in the Connell study were more than two years old, and individuals may survive in captivity for more than three years.
Brush rabbits are preyed on by a variety of species, including bobcat (Felis rufus), coyote (Canis latrans), gray fox (Urocyon cinereoargenteus), long-tailed weasel (Mustela frenata), raptors, and some snakes such as rattlesnakes (Crotalus spp.), and gopher snake (Pituophis melanoleucus). They avoid predation by remaining close to brush and brambles and remain motionless for a period of time when in the open (Chapman 1974). Ectoparasites also may contribute to mortality. For example, Connell (1954) found bot fly larvae (Cuterebra sp.) on a female that appeared lethargic when carrying the larvae and he reported from another study by Mossman the death of a male that had much neck bleeding where two bot fly larvae were lodged.
Dispersal: Brush rabbits appear to be sedentary, but very little specific dispersal data were found for this species. Based on radiotelemetry data for brush rabbits near Corvallis, Oregon, Chapman (1971) concluded that dispersal movements were relatively small. Young brush rabbits were repeatedly trapped at the same trap sites and radio data indicated that they never left the bramble clump in which they were first trapped. Radio-tracking of adult rabbits also indicated that they rarely left the clumps in which they were trapped. In addition, the distances over which brush rabbits were able to successfully home were shorter than other species of Sylvilagus and many other mammals.
Socio-Spatial Behavior: A trapping study of brush rabbits in the Berkeley Hills in northern California indicated that males had larger home ranges than females at all times of the year, and especially in May when females were moving the least (Connell 1954). Based on the maximum diameter of movement, Connell estimated circular average home ranges of 0.95 acre for males and 0.34 acre for females. In the Oregon study by Chapman (1971), brush rabbits had relatively small home ranges. Circular average home ranges based on home range diameters were as follows: 0.27 acre for adult males; 0.41 acre for juvenile males; 0.21 acre for adult females; and 0.17 acre for juvenile females. The size and shape of home ranges of brush rabbits in Oregon reflected the size and shape of bramble clumps. The minimum size of permanently occupied clumps was about 460 sq meters (0.1 acre) (Chapman 1974). Smaller clumps may be occupied, but only if in proximity to larger clumps.
Although the home range estimates above are based on circular ranges calculated from range diameters, range use probably is not circular in shape or uniform, but rather consists of a series of runways that directly connect high use areas within brush habitat. These runways may be used by other small mammals such as voles (Microtus spp.) and western harvest mouse (Reithrodontomys megalotis).
Intraspecific socio-spatial behavior appears to be variable and may reflect local resource conditions. Chapman (1974), for example, cites a study by Zoloth (1969) of brush rabbit behavior on Año Nuevo Island. Several rabbits were observed to feed in the same area simultaneously, but maintained inter-individual distances of one to 24 feet before aggressive chases occurred. On the other hand, Connell (1954) reported that females tended to not overlap while males showed relatively extensive overlap. Connell characterized females as "semiterritorial" but did not observe whether they defended territories. It is not known whether aggregations of brush rabbits serve some kind of social function (e.g., mutual predator detection or social communication) or whether they simply occur as a result of patchy resource distribution.
Connell (1954) estimated population sizes of 0.9 to 2.3 rabbits per acre, but population densities can be expected to vary widely depending on local resource conditions, habitat patchiness, natural fluctuations in population cycles, etc.
Community Relationships: No specific information was found regarding community relationships, but as a herbivore, the brush rabbit can be expected to have significant impacts on vegetation. Zeiner et al. (1990) indicated that brush rabbits may compete with other grazing and browsing species for food. They also occasionally damage Douglas fir (Psuedostuga spp.) seedlings, other seedlings and gardens. It also is prey for a variety of species as listed above.
Physiological Ecology: Very little information on the physiological ecology of brush rabbit was found. According to Zeiner et al. (1990), brush rabbits drink freely in captivity, but there is no information about their free water requirements in the wild.
Disease: Known ecto- and endoparasites of brush rabbits are Hoplopsyllus powersii and Hoplopsyllus minutus, tapeworms (Moscouyia pectinata-americana, Taenia pisiformis), and pinworms (Nematoda: Passalurus ambiguous) (Chapman 1974). Connell (1954) also reports brush rabbits carrying bot fly larvae, which appear to affect their health and in at least one case may have directly caused the death of a male rabbit.
Habitat Loss and Fragmentation: Little data are available on population status and trends of the brush rabbit in western Riverside County, but it can be assumed that the rabbit is vulnerable to urbanization, hunting, and loss of large, contiguous habitat patches.
Little is known of the effects of habitat loss and fragmentation on the viability of brush rabbit populations. A computer simulation study of the New England cottontail (Sylvilagus transitionalis) metapopulations in response to habitat loss and environmental correlations (based on increased vulnerability to predation) showed a rapid decline or extinction of populations (Litvaitus and Villafuerte 1996). This study demonstrated the importance of a habitat management program that maintains habitat connections and habitat suitability (e.g., maintaining early successional habitat). Such factors should be considered in the designation and management of habitat for the brush rabbit in western Riverside County. However, more information on minimum habitat requirements, annual survival, population growth, and dispersal patterns in this species is crucial for examining these effects.
A radiotelemetry study of orientation and homing by brush rabbits in Oregon by Chapman (1971) provides some useful behavioral information that should be considered for design and evaluation of habitat linkages. Chapman observed that rabbits largely restricted their homing routes to brushy cover regardless of the direction or distance. When crossing between clumps, rabbits invariably chose the shortest distance between clumps. Rabbits' homing movements were impeded by human activity and vehicles and they were reluctant to cross roads. Chapman also demonstrated that brush rabbits show little natural dispersal and tend to stay in the clumps in which they were first trapped regardless of age. These findings have important implications for reserve design. Brush rabbits probably will require continuous suitable habitat because they appear unlikely to move long distances through unsuitable habitat. Small, isolated patches of habitat probably are unlikely to support viable populations of brush rabbits.
Chapman, J.A. 1971. Orientation and homing of the brush rabbit (Sylvilagus bachmani). Journal of Mammalogy 52:686-699.
Chapman, J.A. and A.L. Harman. 1972. The breeding biology of a brush rabbit population. Journal of Wildlife Management 36:816-823.
Chapman, J.A. 1974. Sylvilagus bachmani. In: Mammalian Species No. 34:1-4. Published by the American Society of Mammalogists.
Connell, J.H. 1954. Home range and mobility of brush rabbits in California chaparral. Journal of Mammalogy 35:392-405.
Davis, D. E. (ed.) 1982. CRC Handbook of Census Methods for Terrestrial Vertebrates. CRC Press, Inc. Boca Raton, FL.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Litvaitis, J.A. and R. Villafuerte. 1996. Factors affecting the persistence of New England cottontail metapopulations: the role of habitat management. Wildlife Society Bulletin 24:686-693.
Mossman, A.S. 1955. Reproduction of the brush rabbit in California. Journal of Wildlife Management 19:177-184.
Zeiner, D.C., W.F. Laudenslayer, Jr., K.E. Mayer, and M. White. 1990. California Wildlife, Volume III, Mammals. California Statewide Wildlife Habitat Relationships System. Department of Fish and Game, Sacramento, California.
coyote (Canis latrans)
State: None
Federal: None
The coyote population is common and widespread throughout the Plan Area. It occurs in all areas of the Plan Area except the most highly urbanized areas. The coyote is also highly tolerant of human activities and coexists well with humans unless trapped, hunted or otherwise harassed (e.g., disturbance of breeding dens). The coyote is considered to be a Group 1 species because of its broad distribution and the ability to manage for this species on a landscape level.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 489,500 acres (50 percent) of suitable habitat in the Plan Area.
Include within the MSHCP Conservation Area habitat linkages between large habitat blocks. Key habitat linkages that likely will be used by coyotes to move between large habitat blocks include:
For the purpose of the conservation analysis, suitable habitat for the coyote includes all upland and riparian natural habitats and agriculture. Based on this habitat assumption, the Plan Area contains approximately 985,000 acres of suitable habitat for the coyote. Table 1 shows the conservation of suitable habitat for the coyote. Overall, approximately 489,500 acres (50 percent) of suitable habitat in the Plan Area would be conserved in the MSHCP Conservation Area.
The MSHCP database includes several hundred records scattered around the Plan Area, with clusters of records for some areas such as the Santa Rosa Plateau, Lake Mathews-Estelle Mountain, Anza Valley, Lake Skinner/Vail Lake and Banning/Beaumont. Because the coyote is common and widely distributed throughout the Plan Area, this species can be conserved by conserving habitat across the landscape. Although the coyote is highly mobile and capable of moving through lower density residential, rural and agricultural areas, conservation of habitat linkages throughout the reserve system will greatly benefit this species.
TABLE 1
SUMMARY OF HABITAT CONSERVATION FOR COYOTE
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Agricultural Land | 168,363 | 8,542 | 11,482 | 20,024 | 7,319 | 141,020 | 148,339 |
| Chaparral | 413,488 | 64,899 | 207,381 | 272,280 | 59,582 | 81,626 | 141,210 |
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,970 |
| Desert Scrubs | 9,378 | 3,675 | 1,314 | 4,989 | 44 | 4,345 | 4,389 |
| Grassland | 146,869 | 20,011 | 22,806 | 42,817 | 12,223 | 91,829 | 104,052 |
| Meadow | 492 | 0 | 87 | 87 | 18 | 387 | 405 |
| Meadow and Marshes | 470 | 174 | 239 | 413 | 0 | 57 | 57 |
| Montane Coniferous Forest | 29,900 | 17 | 20,485 | 20,502 | 43 | 9,355 | 9,398 |
| Peninsular Juniper Woodland and Scrub | 1,082 | 336 | 274 | 610 | 23 | 450 | 473 |
| Playas and Vernal Pools | 7,914 | 3,828 | 2,923 | 6,751 | 0 | 1,163 | 1,163 |
| Riparian Scrub, Woodland and Forest | 14,607 | 3,920 | 7,273 | 11,193 | 368 | 3,045 | 3,413 |
| Riversidean Alluvial Fan Sage Scrub | 7,149 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,915 |
| Woodlands and Forest | 32,167 | 2,388 | 20,497 | 22,885 | 5,017 | 4,266 | 9,282 |
| TOTAL | 984,565 | 158,122 | 331,379 | 489,501 (50%) |
111,095 (11%) |
383,969 (39%) |
495,066 (50%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Coyotes are highly mobile, with daily movements on the order of 2 to 3 miles (Nowak 1990) and dispersal by juveniles from the parental range typically ranges from 50 to 100 miles (Gier 1975). Habitat connections that serve coyotes, however, probably should not be used as the standard for other wildlife species because they can move through urban landscapes that would not be used by other species such as bobcat and mountain lion (e.g., see Crooks and Jones 1998). At present, coyotes do not appear be excluded from any part of the Plan Area except perhaps the most highly urbanized areas. Nonetheless, several wildlife habitat linkages between large habitat blocks will be conserved. Key habitat linkages that likely will be used by coyotes to move between large habitat blocks are listed under Objective 2.
No specific guidelines for wildlife crossings such as culverts and bridges (i.e., type, size, shape, etc.) are proposed for the coyote because of their adaptability to urban settings, and wildlife crossings for species such as mountain lion and bobcat also will be appropriate for coyotes.
In summary, conservation for the coyote will be achieved by inclusion of 489,500 acres of suitable Conserved Habitat and conservation of key habitat linkages. The Plan Area also is contiguous with coyote habitat in eastern Riverside, San Bernardino, Orange and San Diego counties.
Coyotes will be subject to Incidental Take on lands outside the MSHCP Conservation Area totalling approximately 495,000 acres (50 percent) of suitable habitat. Of this unconserved habitat, about 148,000 acres are existing agricultural land that may continue to provide some habitat value in the future. Also, of the 495,000 acres authorized for Incidental Take, approximately 111,000 acres are in the Rural/Mountainous designated areas. Although increased negative interactions between coyotes and humans are anticipated in the Rural/Mountainous areas (e.g.,vehicle collisions, disturbance of dens, and possibly animal control actions where coyotes become pests or are perceived as a danger to public health and safety), coyotes likely will still use these areas.
The MSHCP database includes 330 records for the coyote. Of the 330 records, 153 (46 percent) are precision code ‟1" (an ‟x" and ‟y" coordinate that allows for good precision in the location), 34 (10 percent) are precision code ‟2" (one ‟x" or ‟y" coordinate or equivalent), and the remaining 143 (43 percent) are precision codes ‟3" or ‟4" (relatively imprecise locations from general areas). Most of the records are relatively recent, with 268 (81 percent) since 1990 and 55 records (17 percent) from 1947-1989. Eight records have no observation date. Data records for the coyote are distributed throughout the Plan Area, with clusters on the Santa Rosa Plateau, Lake Skinner, Sage, Lake Mathews, Anza Valley, and Banning/Beaumont. Based on the recency of most of the data and the distribution of records throughout the Plan Area, the database appears to provide a fairly good representation of the population distribution of this species in the Plan Area, although the frequency of observations in certain areas may reflect more the reporting patterns that the density of coyote populations.
Coyotes utilize all habitats types and often are found in urban areas adjacent to open land. Primary habitats include grasslands, short-grass prairies, semiarid sagebrush, and broken forests (Gier 1975). Within their geographic range, coyotes are limited by the absence of open areas (Gier 1975). Natal dens are associated with brush-covered slopes, thickets, hollow logs, rocky ledges, and burrows. For example, in eastern Maine, dens varied from shallow depressions to multi-chambered burrows extending 1-2 meters in depth (Harrison and Gilbert 1985).
The coyote has been recorded within virtually all upland and riparian habitat and land cover types in the MSHCP Plan Area. The majority of the 330 records are from chaparral (69 records or 21 percent of the total). Sixty-five (20 percent) of the records are from scrub habitats (coastal scrub, Diegan coastal sage scrub, Riversidean alluvial fan scrub, Riversidean sage scrub, big sagebrush scrub and desert scrub), 61 (18 percent) from annual and native grassland, 53 (16 percent) from field crops and grove/orchard, seven (2 percent) from oak woodlands (coast live oak woodland, dense Engelmann oak woodland, oak woodland), two (< 1 percent) from riparian (riparian scrub, southern cottonwood-willow riparian), three (1 percent) from lower montane coniferous forest, one (<1 percent) from desert scrub and one (<1 percent) from alkali playa. Sixty-eight (20 percent) of the records are from residential/urban/exotic.
The coyote's geographic range has expanded dramatically in the last 150 years and includes the contiguous United States, western Canada and eastern Alaska, north to Hudson Bay and south to Guatemala (Hall 1981). Marginal records for the subspecies C. l. clepticus are San Marcos, Julian, and Jacumba in San Diego County, and into Baja California, Mexico (Hall 1981). The type locality for the subspecies is from the San Pedro Martir Mountains in Baja California (Bekoff 1977). The range of the subspecies appears to include western Riverside County, but the boundary with the range of the subspecies to the north, C. l. ochropus, is not clearly defined (Hall 1981).
The coyote occurs throughout the Plan Area.
All Plan Area bioregions.
Genetics: The diploid number of chromosome of the coyote is 78 (Wayne 1998). Phylogenetically, the coyote is closely related to the gray wolf (Canis lupus) and Simien jackal (Canis simensis) based on allozyme genetic distance and chromosome morphology (Wayne 1998). Studies of coyote mitochondrial DNA (mtDNA) genotypes indicate little geographic variation and the same genotypes may be present at widely-spaced localities (Wayne 1998). Lehman and Wayne (1991) found 32 mtDNA genotypes in coyotes from most parts of their North American range. The genotypes were not strongly geographically segregated, indicating high gene flow between subpopulations. Genetic relationships among populations of coyotes also are confusing because interbreeding between dogs and coyotes, coyotes and gray wolves, and coyotes and red wolves (Canis rufus) is not uncommon. Brownlow (1996) indicates that the molecular genetic studies have determined that the red wolf is in fact a hybrid of the gray wolf and coyote. Consequently the currently described subspecies of coyote may not hold up under molecular genetic analyses.
Diet and Foraging: Coyotes are omnivores, but basically carnivores, and their diet strongly reflect the prey and other food items available (Andelt et al. 1987; Gier 1975). Gier (1975), for example, lists the following food items: bison, deer, elk, sheep, rabbits, rodents, birds, non-toad amphibians, lizards, most snakes, crustaceans, insects, blackberries, blueberries, peaches, apples, pears, prickly-pear cactus apples, chapotes, persimmons, peanuts, watermelon, cantaloupe, and grasses. They also consume inedible but chewable items such as harness straps, rubber or leather shoe soles, scraps of automobile tires, and paper wrappings. Coyotes prefer fresh meat, but will scavenge carrion. Coyotes also can be a major predator on domestic animals and pets such as cattle, lambs, chickens, turkeys, ducks, cats and dogs. For example, Crooks (unpublished manuscript) found cat remains in 21 percent of coyote scats in urban fragments in southwestern San Diego County. In central and southern California, lagomorphs (rabbits and hares) and rodents are primary prey items (Cypher et al. 1996; Pierce et al. 2000; Weintraub 1986).
Although coyotes are opportunistic omnivores, there is some evidence of differential use of food items by age class that probably reflects foraging experience. Cypher et al. (1996) found that pups (<1 year of age) in the southern Central Valley of California consumed more insects than did yearlings (1 year of age) and adults (> 1 year of age). Also, adults and yearlings differed in their secondary food selection (jackrabbits were the primary prey of both age groups); adults' secondary prey was mostly rodents while yearlings' secondary prey was livestock and rodents.
Coyotes also exhibit seasonal selection of prey, probably in relation to availability. Smith (1990) found that coyotes' diet shifted from small mammals such as kangaroo rats (Dipodomys spp.), voles (Microtus sp.), and squirrels (Spermophilus sp.) in the spring to fruit (manzanita berries) in the fall.
Coyotes generally hunt by coursing in open areas, where they approach, test, and pursue prey, but they also may sit and wait for smaller prey. Also, in some areas with cover, they use the cover to allow them to approach prey more closely before they pounce (Murray et al. 1995). Coyotes also may occasionally hunt in packs for larger or difficult prey (Gier 1975). Rathbun et al. (1980) documented a family group of a male, female, and two-year old male offspring attacking and killing a badger (Taxidea taxus). When taking large prey such as mule deer (Odocoileus hemionus), coyotes hunt in packs. However, there is no evidence that they select for deer in poor condition as do some other carnivores (Pierce et al. 2000).
Coyotes exhibit hunting associations with badgers in some parts of their range. Minta et al. (1992) observed coyotes and badgers hunting in association for Uinta ground squirrels (Spermophilus armatus) in northwestern Wyoming. When hunting with badgers in brushy vegetation, coyotes were more successful than hunting alone because badgers would flush squirrels to the surface. The badger, which hunts underground, benefitted as well because squirrels tended to enter and stay in burrows in the presence of coyotes, thus increasing the capture success of the badger.
Coyotes can be sustained on about 400-600 g of meat per day, or about 250 kg per year (Gier 1975).
Daily Activities: Coyotes may be active anytime of the day, but primarily are nocturnal and crepuscular (Nowak 1990). A coyote typically travels about 4 km (2.5 miles) during a night of hunting (Nowak 1990). Daily movements, however, also depend on reproductive activities. During the nursing season, males and females spend more time near the den. Daily movements increase during weaning and are much larger when the pups are weaned, probably because of the increased energetic needs of the pups and the requirement of larger prey (Harrison and Gilbert 1985). Human disturbances may modify the temporal and spatial pattern of coyote activities. For example, Gese et al. (1989) studied the effects of military training activity on coyote movements in Colorado and found that individual coyotes responded differently depending on the amount of cover in their range and the level of military activities. Coyotes with high cover and little military activity in their range contracted their ranges, while coyotes with little cover and moderate levels of military activity in their range expanded their ranges. Also, coyotes generally increased their level of diurnal activity in relation to training activities; presumably to maintain space between themselves and the activities.
Reproduction: Coyotes are monestrous, meaning that females only come into estrus once per year (Gier 1975) and lost litters are not compensated for in the same breeding season. Receptivity typically occurs in mid- to late-winter (January to March) and may last up to a month. About 90 percent of adult females are sexually active and 0-60 percent of "yearling" (9-10 months) are active during this period. Receptive females attract several male consorts and may mate with several males, which the female appears to select. Ovulation occurs about three to four days before the end of receptivity. Gestation is about 58 to 65 days. Litter sizes range from two to 12 pups, but some dens may contain more than one litter.
Males and females establish a pairbond, whereupon they select a territory, prepare a den, hunt and sleep together during the pregnancy, and both provide care for the pups (Gier 1975). The male is the primary hunter during the nursing and weaning period and food is brought back to the den and regurgitated for the pups. The territory around the den is defended from predators and other coyotes. Pups are weaned by 8-10 weeks, at which time the den is abandoned (Harrison and Gilbert 1985). At this time, the pups concentrate their activity around rendezvous sites, and over time adult visits to the rendezvous sites become progressively less frequent. The family unit may remain intact until about November, but pups may wander long distances in November and December. Adult weights are achieved by the ninth month.
Survival: Coyotes live about ten years (Gier 1975), but mortality in the first year is high. About 10-15 percent of the pups die within a few days of birth from several causes, including parasitic infections (hookworm, roundworm), accidents, predation (hawks, owls, eagle), neighboring coyotes, the loss of the parents, and general physical weaknesses. By late summer, about 50 percent of the pups may have perished.
Dispersal: Coyotes are highly mobile and capable of moving long distances. Young disperse in the fall and winter and may move 80-160 km (50-100 miles) from the parental range (Gier 1975). In Iowa, individuals traveled an average of 31 km (19 miles), but up to 323 km (200 miles) (Nowak 1990).
Socio-Spatial Behavior: Coyotes typically establish consistent home ranges and exhibit fairly extensive intraspecific home range overlap (Gier 1975). Home ranges may be quite variable, with a range of 10-100 sq km (Laundré and Keller 1984). Coyotes apparently are only strongly territorial during the denning season when their pups are at risk of being killed by other coyotes (Gier 1975). As described above, coyotes may come together to hunt in packs comprised of a family unit or a temporary non-family "pack" of two to six individuals comprised of bachelor males, non-reproductive females, and near-mature young. Their spatial structure is related to the adequacy, type, and distribution of the food supply (e.g., a pack is required to take larger prey such as deer), denning territory, and intraspecific and interspecific competition for resources.
Human disturbances may cause coyotes to alter their spatial behavior, such as the use of their home range and dens. As described above, Gese et al. (1989) found that coyotes shifted their ranges and centers of activity in response to military training activities. Harrison and Gilbert (1985) observed that coyotes moved their dens after human disturbance. On the other hand, range management practices in south Texas did not appear to have substantial effects on coyotes' establishment and use of home ranges (Bradley and Fagre 1988). In this study on an experimental ranch, roads and fencelines did not limit home range establishment, and, in fact, animals tended to use roads and fencelines for movement more than expected by chance. There was a slight avoidance of pastures with cattle.
Coyotes are a highly social species and use a variety of techniques to mark their ranges, probably to communicate their presence and location, and to attract the opposite sex (Gier 1975). They primarily communicate through calls and scent marking with urine and feces; urine markings attract the opposite sex more than the same sex.
Community Relationships: A number of studies have demonstrated interesting and unique community relationships between coyotes and other species. For example, as discussed above, coyotes exhibit an interesting mutualistic hunting association with badgers at least in part of their range (Minta et al. 1992).
Foremost, coyotes, as an upper trophic carnivore, have a profound effect on prey populations, and consequently on the faunal and floral composition of the communities supporting the prey populations. Perhaps one of the most important findings about coyotes, at least in regard to conservation planning, is the impact that coyotes have on the faunal composition of fragmented scrub habitats in southern California. Crooks and Soulé (1999) documented that the coyote is an important component of the southern California ecosystem because they appear to control the abundance of native and non-native mesopredators (striped skunk [Mephitis mephitis], gray fox [Urocyon cinereoargenteus], raccoon [Procyon lotor], Virginia opossum (Didelphis virginiana), and domestic cat [Felis cattus]) that prey on smaller native wildlife such as birds and rodents. They found that where coyotes are absent or rare, mesopredator abundance is high. They also found that high mesopredator abundance in a habitat fragment is associated with low numbers of native scrub specialist bird species. That is, coyotes appear to be important for maintaining native fauna in fragmented landscapes.
Coyotes may be in direct competition for resources with several other carnivorous species, including wolves, black bear (Ursus americanus), mountain lion (Puma concolor), bobcats and lynxes (Felis spp.), gray foxes, red foxes (Vulpia vulpia), and kit foxes (Vulpia macrotis). To some extent, the coyote's range and diet overlap these species. Cypher and Spencer (1998) examined interactions between coyotes and the San Joaquin kit fox and found that coyotes may engage in "interference competition" with kit foxes, including killing kit foxes, but not eating them. Both species' primary prey in the Central Valley southwest of Bakersfield are jackrabbits (Lepus californicus) and cottontail rabbits (Sylvilagus spp.), but kit foxes also consume kangaroo rats and other smaller prey (including insects) at a higher frequency than coyotes. Cypher and Spencer (1998) suggest that kit foxes employ food partitioning, greater dietary breadth, and year-round den use to coexist with coyotes. So although there is evidence of resource partitioning, competitive interactions probably become intense during low overall prey availability.
Sargeant et al. (1987) studied spatial relations of coyotes and red foxes in North Dakota and observed that coyotes and foxes tended to avoid interactions, with avoidance the greatest during the summer when both species have pups. Use of their overlap areas and direct encounters were less than expected by chance. Sargeant et al. concluded that coyotes affected the abundance of the red fox in the Plan Area.
Coyotes probably have few predators, but predation by mountain lions has been documented (Boyd and O'Gara 1985).
Physiological Ecology: No information on coyote physiology was reviewed beyond their reproductive physiology. However, because of the coyote's recent and widespread distribution in North and Central America, it is assumed that the coyote does not possess, nor is limited by, any special physiological adaptations to different environments. Adaptations to local conditions (e.g., arid environments) are more likely to be behavioral, such as restricting activity periods to times that minimize energetic expenditure, etc.
Rangewide, the coyote is not threatened with extinction and this species will persist in western Riverside County under any reserve scenario. However, its distribution in the MSHCP Plan Area likely will be affected by the pattern of urbanization and fragmentation and isolation of patches of habitat that may be inaccessible or too small to attract or sustain a coyote population. As described above and reiterated below, the loss of coyotes may result in the decline of species richness in small habitat patches through the loss of the native fauna to mesopredators. Exacerbating the loss of coyotes in urban habitat patches is the increased risk of vehicle collisions and any predator control activities conducted by local agencies.
Although the coyote is not at risk of extirpation from the MSHCP Plan Area, it appears to be a key species in maintaining species richness in smaller habitat fragments. Conceptually, habitat fragmentation may alter the composition and structure of animal communities by modifying several ecological processes, including predation. Predators may respond to landscape features that are affected by habitat fragmentation, such as proximity to habitat edges, size of habitat patches, and habitat diversity. For example, edges may act either as physical barriers or movement conduits, causing predators to move along them and thus encounter prey at the edge at a higher rate. In addition, predator densities (and prey vulnerability) may be higher in small habitat patches, particularly for some generalist predators whose patches of habitat are surrounded by matrices that offer human-derived foods (see Oehler and Litvaitis 1996). As demonstrated by the work by Crooks in San Diego County, coyotes can help maintain native fauna by controlling mesopredators such as raccoons, skunks, gray foxes, and feral and domestic house cats (Crooks and Soulé 1999; Crooks unpublished manuscript). Consequently the reserve system should allow coyotes access to as much of the reserve as possible.
Andelt, W.F., J.G. Kie, F.R. Knowlton, and K. Cardwell. 1987. Variation in coyote diets associated with season and successional changes in vegetation. Journal of Wildlife Management 5:273-277.
Bekoff, M. 1977. Mammalian Species: Canis latrans. 79:1-9.
Boyd, D. and B. O'Gara. 1985. Cougar predation on coyote. The Murrelet 66:17.
Bradley, L.C. and D.B. Fagre. 1988. Coyote and bobcat responses to integrated ranch management practices in south Texas. Journal of Range Management 41:322-327.
Brownlow, C.A. 1996. Molecular taxonomy and the conservation of the red wolf and other endangered species. Conservation Biology 10:390-396.
Crooks, K.R. unpublished manuscript. Relative sensitivities of mammalian carnivores to habitat fragmentation.
Crooks, K.R. and D. Jones. 1998. Monitoring program for carnivore corridor use in The Nature Reserve of Orange County. Annual Report prepared for The Nature Reserve of Orange County. 24 pp + appendices.
Crooks, K.R. and M.E. Soulé. 1999. Mesopredator release and avifaunal extinctions in urban habitat fragments. Nature 400:563-566.
Cypher, B.L. and K.A. Spencer. 1998. Competitive interactions between coyotes and San Joaquin kit foxes. Journal of Mammalogy 79:204-214.
Cypher, B.L., K.A. Spencer, and J.H. Scrivner. 1996. Use of food items by sex and age classes of coyotes. California Fish and Game 82:42-47.
Gese, E.M., O.J. Rongstad, and W.R. Mytton. 1989. Changes in coyote movements due to military activity. Journal of Wildlife Management 53:335-339.
Gier, H.T. 1975. Ecology and behavior of the coyote (Canis latrans). In The Wild Canids, M.W. Fox (ed.), Van Nostrand Reinhold, New York, pp. 247-262.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York, 2 Vol. 1181 pp.
Harrison, D.J. and J.R. Gilbert. 1985. Denning ecology and movement of coyote (Canis latrans) in Maine during pup rearing. Journal of Mammalogy 66:712-719.
Laundré, J.W. and B.L. Keller. 1984. Home-range size of coyotes: a critical review. Journal of Wildlife Management 48:127-139.
Lehman, N. and R.K. Wayne. 1991. Analysis of coyote mitochondrial DNA genotype frequencies: estimation of the effective number of alleles. Genetics 128:405-416.
Minta, S.C., K.A. Minta, and D.F. Lott. 1992. Hunting associations between badgers (Taxidea taxus) and coyotes (Canis latrans). Journal of Mammalogy 73:814-820.
Murray, D.L., S. Boutin, M. O'Donoghue, and V.O. Nams. 1995. Hunting behaviour of a sympatric felid and canid in relation to vegetative cover. Animal Behaviour 50:1203-1210.
Nowak, R.M. 1991. Mammals of the World, Fifth Edition. The Johns Hopkins University Press, Baltimore. pp.1068-1070.
Oehler, J.D. and J.A. Litvaitis. 1996. The role of spatial scale in understanding responses of medium-sized carnivores to forest fragmentation. Canadian Journal of Zoology 74:2070-2079.
Pierce, B.M., V.C. Bleich, and R.T. Bowyer. 2000. Selection of mule deer by mountain lions and coyotes: effects of hunting style, body size, and reproductive status. Journal of Mammalogy 81:462-472.
Rathbun, A.P., M.C. Wells, and M. Bekoff. 1980. Cooperative predation by coyotes on badgers. Journal of Mammalogy 61:375-376.
Sargeant, A.B. and S.H. Allen. 1989. Observed interactions between coyotes and red foxes. Journal of Mammalogy 70:631-633.
Smith, J.R. 1990. Coyotes diets associated with seasonal mule deer activities in California. California Fish and Game 76:78-82.
Wayne, R.K 1998. Molecular evolution of the dog family. [http://www.kc.net/].
Weintraub, J.D. 1986. Coyote diets, five years later at Cuyamaca Rancho State Park. Bulletin of the Southern California Academy of Sciences 85:152-157.
Dulzura kangaroo rat (Dipodomys simulans)
State: None
Federal: None
The Dulzura kangaroo rat occurs throughout the Plan Area in coastal sage scrub (including Diegan and Riversidean upland sage scrubs and alluvial fan sage scrub), sage scrub/grassland ecotones, chaparral, and desert scrubs at all elevations up to 2,600 feet. This species is considered to be fairly common in suitable habitat. No specific management regimes are needed to maintain an adequate amount of habitat for this species, although management of habitat for species such as the Stephens' kangaroo rat, San Bernardino kangaroo rat, Los Angeles pocket mouse and California gnatcatcher may benefit the Dulzura kangaroo rat.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 198,200 acres (58 percent) of suitable habitat in the Plan Area. The majority of conservation will occur in the following existing and proposed Core Areas: Existing Core C (15,610 acres), Existing Core F (8,360 acres), Existing Core G (4,490 acres), Existing Core H (17,470 acres), Existing Core I (9,610 acres), Existing Core J (24,370 acres), Existing Core M (10,460 acres), Proposed Core 1 (7,470 acres), Proposed Core 2 (5,050 acres), Proposed Extension of Existing Core 2 (8,100 acres), Proposed Core 3 (24,920 acres), Proposed Core 4 (11,890 acres), Proposed Core 5 (3,220 acres), and Proposed Core 7 (50,000 acres).
Include within the MSHCP Conservation Area approximately 21,000 acres of dispersal and/or movement linkages between core habitat blocks, including the following: Proposed Linkage 3 (5,540 acres), Proposed Linkage 8 (5,470 acres), Proposed Linkage 10 (1,520 acres), Proposed Linkage 11 (1,670 acres), Proposed Linkage 13 (1,920 acres), Proposed Linkage 14 (4,320 acres), and Proposed Linkages 17 and 18 (610 acres).
Documented locations for the Dulzura kangaroo rat are not included the MSHCP database. Until recently when this species was split from the Pacific kangaroo rat (Dipodomys agilis), the Dulzura kangaroo rat was not considered sensitive and location records were not submitted to the CNDDB. However, this species s relatively common in chaparral, coastal sage scrub (including Riversidean and Diego coastal sage scrub), Riversidean alluvial fan sage scrub and peninsular juniper woodland throughout the Plan Area up to approximately 2,600 feet in elevation. This species also often occurs in grasslands adjacent to occupied chaparral and scrub habitats (i.e., the grassland-shrub ecotone) where the Stephens' kangaroo rat is absent (Behrends, pers.obs.), but the grassland ecotone area is not included in the analysis because it cannot be accurately quantified. Based on these conservative assumptions about habitat, the Plan Area supports at least 345,000 acres of suitable habitat for the Dulzura kangaroo rat. Table 1 shows the conservation of suitable habitat for the Dulzura kangaroo rat. Overall, approximately 198,200 acres (58 percent) of suitable habitat in the Plan Area would be included in the MSHCP Conservation Area.
The Dulzura kangaroo rat is still relatively common and is found in suitable habitat throughout the Plan Area at elevations up to about 2,600 feet. It is common in the existing, extended existing and proposed Core Areas, including Lake Mathews-Estelle Mountain, Steele Peak, San Jacinto Wildlife Area-Lake Perris, Lake Skinner-Diamond Valley Lake, the Badlands, Vail Lake-Sage, and along the lower elevation foothills of the Santa Ana Mountains, Santa Rosa Plateau, Agua Tibia Wilderness, San Jacinto Mountains, and San Bernardino Mountains.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
DULZURA KANGAROO RAT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 193,762 | 46,640 | 71,086 | 117,726 | 42,605 | 33,431 | 76,036 |
| Coastal Sage Scrub | 142,762 | 44,006 | 30,096 | 74,102 | 25,137 | 43,523 | 68,660 |
| Desert Scrub | 1,528 | 1,489 | 3 | 1,492 | 36 | 0 | 36 |
| Riversidean Alluvial Fan Sage Scrub | 5,850 | 3,030 | 1,348 | 4,378 | 173 | 1,299 | 1,472 |
| Peninsular Juniper Woodland | 947 | 336 | 183 | 519 | 23 | 405 | 428 |
| TOTAL | 344,849 | 95,501 28% |
102,716 30% |
198,217 58% |
67,974 20% |
78,658 22% |
146,632 42% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Despite its wide distribution in the Plan Area, little is known about the relationship between populations of the Dulzura kangaroo rat in the different parts of the Plan Area. No studies have been performed to determine whether there are genetic differences in geographically distinct populations that would be important for reserve configuration, and thus whether genetic exchange between reserve areas would be important for sustaining viable populations. Kangaroo rats are relatively mobile compared to other closely related rodents such as pocket mice and they are capable of dispersing long distances as long as suitable habitat is available (including game and off-road vehicle trails and dirt roads). Also, they readily cross paved roads. For this analysis, and based on radiotelemetry data collected for the sympatric Stephens' kangaroo rat by Price et al. (1994), it is assumed that Dulzura kangaroo rats are able to disperse at least 400 meters (1,300 feet) between suitable habitat patches. Given the existing distribution of suitable habitat and the configuration of the MSHCP Conservation Area, four main habitat complexes for the Dulzura kangaroo rat were identified:
Smaller habitat areas assumed to be isolated from the larger habitat complexes are the Jurupa Mountains, Box Springs Mountain, Lakeview Mountains, Sycamore Canyon Regional Park, Norco Hills, Double Butte, Motte-Rimrock Reserve, and Warm Springs Creek. Although these areas meet the minimum area of 60 acres suggested by Bolger et al. (1997) to sustain native rodent populations, Dulzura kangaroo rats in these areas may still be at relatively high risk of extirpation because a single catastrophic event such as a wildfire or even extreme predation pressure could devastate a local population to a level beyond recovery.
The Santa Ana Mountain foothills form a large, contiguous habitat area (~70,000 acres) comprised of reserve and rural mountainous areas. This habitat complex also includes extensive contiguous habitat in north San Diego County. Much of this area is chaparral and mesic coastal sage scrub. Major paved roads in this area (Highway 74 between Lake Elsinore and Orange County, Clinton Keith Road/Tenaja Road and De Luz Road) probably do not constrain dispersal by Dulzura kangaroo rats because they are two-lane; however, roadkill on Highway 74 probably is substantial because of the high volume of commuter traffic.
Lake Mathews-Estelle Mountain is generally contiguous with the Steele Peak reserve area. The combined MSHCP Conservation Area in this habitat complex is approximately 31,000 acres. State Highway 74 is a potential barrier to movement to the Kabian Park area and Railroad Canyon Road is a potential barrier to movement between Kabian and the Sedco Hills because of the high volume of traffic on these roads. Culverts under these roads would allow for movement of Dulzura kangaroo rats between these areas. There is also high potential for Dulzura kangaroo rats to move between this habitat complex and the Santa Ana Mountains foothills along Indian Canyon or Horsethief Canyon.
By far the largest intact habitat complex for the northwestern Dulzura kangaroo rat is the Badlands-San Jacinto Mountain foothills-Agua Tibia Wilderness complex. This area comprises approximately the eastern one-third of the Plan Area. With the exception of several major highways, continuous habitat for the Dulzura kangaroo rat runs from the northwest extent of the Badlands north of Moreno Valley south to the foothills of the San Jacinto Mountains in the area of Sage and farther south to the Agua Tibia Wilderness. The southern part of this habitat complex also is contiguous with habitat in San Diego County. This complex also includes the San Jacinto Wildlife Area-Lake Perris and Lake Skinner-Diamond Valley Lake Core Areas.
Major roads that interrupt this large habitat area include the following:
It should be noted that a substantial amount of the Badlands habitat is designated rural mountainous, which will provide some habitat for the Dulzura kangaroo rat, but which is not in the MSHCP Conservation Area. Given the steep topography in the Badlands, it is highly likely that the majority of the area will remain undeveloped and remain suitable for the Dulzura kangaroo rat. A large portion of suitable habitat in the Sage area also will be designated rural mountainous, but adequate reserve in the Criteria Area will be assembled as part of the MSHCP Conservation Area in this area to maintain habitat connections.
The Banning Bench complex includes continuous habitat along the foothills of the San Bernardino Mountains, with most of the suitable habitat for the San Diego pocket mouse in San Bernardino County.
In summary, the MSHCP Conservation Area will include at least 198,200 acres (58 percent) of suitable habitat. With implementation of the MSHCP, populations of the Dulzura kangaroo rat should remain viable in the Plan Area.
Approximately 146,632 acres (42 percent) of suitable habitat for the Dulzura kangaroo rat would be outside the MSHCP Conservation Area.
The reader should note that most of the literature cited in this section considered the Dulzura kangaroo rat to be the Pacific (agile) kangaroo rat (D. agilis) at the time the studies were conducted. As described below, since about 1997 the Dulzura kangaroo rat has been accepted as a distinct species based on chromosomal and morphometric data (Sullivan and Best 1997). Studies where its clear, based on geographic and elevational range, that the kangaroo rats species under study was the Dulzura kangaroo rat, the species is assumed to be the Dulzura kangaroo rat. For example, for studies by Price and her colleagues in western Riverside County (e.g., Price et al. 199l; Price and Goldengay 1992; Goldengay and Price 1997), it is assumed that the Pacific kangaroo rat referred to in the studies is the currently named Dulzura kangaroo rat.
The MSHCP database and CNDDB do not include records for the Dulzura kangaroo rat. This species is not designated by CDFG as California Special Concern species and thus CNDDB records for the species are not kept. However, this species is still relatively common in the Plan Area and populations can be inferred on the basis of habitat associations and elevation.
The Dulzura kangaroo rat occurs in open microhabitats in chaparral, coastal sage scrub (including Riversidean and Diego coastal sage scrub), Riversidean alluvial fan sage scrub and peninsular juniper woodland throughout the Plan Area up to approximately 2,600 feet in elevation. The approximate elevation limit for this species is based on Sullivan and Best (1997). Williams et al. (1993) describe the habitat of the Dulzura kangaroo rat as coastal chaparral (which would include coastal sage scrub) and grassland communities. However, trapping studies in western Riverside County often demonstrate that the Dulzura kangaroo rat is absent in grasslands occupied by the sympatric Stephens' kangaroo rat (Dipodomys stephensi) (Behrends, pers. obs.). Furthermore, studies by Price and her colleagues (Price et al. 199l; Price and Goldengay 1992; Goldengay and Price 1997) clearly showed that in areas where the Stephens' kangaroo rat and Dulzura kangaroo rat overlap, the Dulzura kangaroo rat was captured in areas with significantly greater shrub and rockier cover than the Stephens' kangaroo rat. Price et al. (1991) demonstrated that Dulzura kangaroo rats forage under shrub canopies and avoid lighted open areas more than Stephens' kangaroo rat. The Stephens' kangaroo rat appears to be socially dominant over the Dulzura kangaroo rat (Bleich and Price 1995) and may actively exclude them from grassland habitat. In the absence of the Stephens' kangaroo rat, Dulzura kangaroo rats often occur in grasslands that are near chaparral or coastal sage scrub (Behrends, pers. obs.). Also, Price and Waser (1984) found that Dulzura kangaroo rats increase in abundance following wildfires that create openings in chaparral and sage scrub habitats.
According to Sullivan and Best (1997), the Dulzura kangaroo rat ranges from approximately the foothills east of Ventura and north of the Santa Clara River Valley south to approximately Magdalena Plain, Baja California, Mexico. The species occurs at elevations below approximately 2,600 feet in the Transverse and Peninsular mountain ranges, with sampled populations from Soliment Canyon in Ventura County, Cajon Pass in San Bernardino County, Lake Mathews and Cabazon in Riverside County, San Luis Rey Valley, Warner Springs, San Diego and Jacumba in San Diego County, and Ensenada, Sierra Juarez, Valle de Trinidad, San Quintin Plain, San Pedro de Martir, El Rosario, San Agustin, Santa Catarina, Laguna Chapala, San Andres, Mesquital, San Ignacio and Magdalena Plain in Baja California, Mexico. It can be assumed that the Dulzura kangaroo rat occurs in sage scrub, chaparral and other mesic to xeric shrub vegetation communities (e.g., desert scrubs, pinyon-juniper woodlands within the Upper Sonoran Zone) within this geographic and elevational range.
Throughout coastal sage scrub, chaparral and shrub/grassland ecotones at elevations up to 2,600 feet throughout the Plan Area.
Same as above.
Genetics: The Dulzura kangaroo rat is one of 19 species of kangaroo rat and is placed in the heermanni group of kangaroo rats (Patton and Rogers 1993). The Dulzura kangaroo rat recently was distinguished from the Pacific (agile) kangaroo rat (D. agilis) from what formerly was considered to be two chromosomal forms of the Pacific kangaroo rat (Best et al. 1986; Sullivan and Best 1997). The southern, lower elevation chromosomal form with a diploid number of 60 was distinguished from the northern, higher elevation chromosomal form with a diploid number of 62. The southern chromosomal form was determined to be a distinct species and is referred to as the Dulzura kangaroo rat (D. simulans) (also sometimes referred to in the literature as the San Diego kangaroo rat), while the northern form is still named the Pacific or agile kangaroo rat (D. agilis). Sullivan and Best (1997a) also examined morphological variation in external, cranial and bacular (penis bone) characteristics and found significant differences between the two species. Based on chromosomal data, the Dulzura kangaroo rat is closely related taxonomically to the chisel-toothed kangaroo rat (D. microps), big-eared kangaroo rat (D. elephantinus), and the narrow-faced kangaroo rat (D. venustus), all of which have a diploid number of 60.
Diet and Foraging: Little scientific literature is available on the specific diet of the Dulzura kangaroo rats in the wild, but like all kangaroo rats, they are primarily granivores (seed eaters) and probably are opportunistic in the collection of seeds. In a laboratory study of native seed selection, however, Dulzura kangaroo rats were found to select first the seeds of Avena and Erodium (large seeds) over those of Encelia and Phacelia (small seeds) (Price et al. 1991). They also probably ingest herbaceous material and insects when available. They collect seeds from the substrate into fur-lined cheek pouches for transport. However, it is unknown whether they store them in scattered surface caches in the vicinity of their home burrows or larder hoard them in their home burrows.
Daily Activities: Dulzura kangaroo rats and all other kangaroo rats are primarily nocturnal animals, but they also exhibit crepuscular behavior around dusk and dawn. They emerge from their day burrows around dusk to engage in foraging and other activities. Kangaroo rats may be active any hour of the night, but the heaviest concentration of activity tends to occur in the three to four hour time span just after dusk (Behrends, pers. obs.). Burrows are often plugged during the daytime.
Reproduction: There are no direct reproduction data for the Dulzura kangaroo rat. The following information, mostly summarized by Randall (1993), is generalizable to the genus Dipodomys.
Kangaroo rats in general have relatively low reproductive output for rodents. However, kangaroo rats are opportunistic breeders and can reproduce several times a season (polyestrous) and at any time of the year (Smith and Jorgensen 1975). Breeding activities appear to vary in relation to ecological conditions. Reproduction typically occurs following rainfall and production of herbaceous annuals. Individuals may not breed in years when conditions are poor. Studies indicate that nearly all adult individuals in a population are capable of breeding, but the proportion of individuals active at non-peak breeding periods (e.g., late summer-early fall) may be smaller (e.g., Kenagy 1973). Males may remain fertile for long periods of time and they typically are reproductive before females come into reproductive condition. The published range of average litter sizes for kangaroo rats is 2.5 pups for the banner-tailed kangaroo rat (D. spectabilis) to 3.5 pups for the Panamint kangaroo rat (D. panamintinus), with seven other species falling within this range (Eisenberg 1993; Daly et al. 1984). It can be safely assumed that the typical litter size of the Dulzura kangaroo rat falls within or close to the range of 2 to 4 pups per litter.
Survival: Typical life expectancy of kangaroo rats is less than one year, but individuals may live up to 6-7 years in captivity. There are no published data on the life expectancy of the Dulzura kangaroo rat in the field, although Best indicates an average life span of 10 months in a general account of the species in Wilson and Ruff (1999). Based on recapture data, McCloskey (1972) estimated average monthly survival percentages of males at 79 percent and females at 80 percent, with a range of 52 to 100 percent. McCloskey did not detect any seasonal or sex-specific relationships with survivorship. Known and likely predators of kangaroo rats in western Riverside County include coyotes, gray foxes, bobcats, long-tailed weasels, various snakes, owls, and shrikes.
Dispersal: There are no specific data on dispersal by the Dulzura kangaroo rat. The few data available on dispersal in kangaroo rats indicates two species with female bias in dispersal (D. heermani and D. spectabilis), one species with male bias (D. merriami) and one species with no discernable differences (D. stephensi) (Jones 1993; Price et al. 1994). Based on this variation, no generalizations about dispersal in the Dulzura kangaroo rat can be drawn. The only data specifically for the Dulzura kangaroo rat related at all to dispersal is from McCloskey's (1972) recapture data. He determined that the average duration of residence by an individual was 4.4 months, but the variation was high (standard error of 3.4 months). Some individuals were resident for more than a year and others were present only two or three months. Recruitment of juveniles into the population also is unknown, but it probably varies in relation to breeding activities and ecological conditions (i.e., carrying capacity of the habitat).
Socio-Spatial Behavior: The only published data on socio-spatial behavior of the Dulzura kangaroo rat is from MacMillen (1964) who reported that male and female home ranges were equivalent in size (average of 0.8 acre, range of 0.4 to 1.5 acres) and that male home ranges overlapped females and other males more than female ranges overlapped ranges of other females. This pattern is similar to other kangaroo rat species for which spatial information is available, including D. merriami, D. ordi, D. panamintinus, and D. ingens (Jones 1993).
Community Relationships: The community ecology of heteromyid rodents, including kangaroo rats (Dipodomys spp.), pocket mice (Perognathus and Chaetodipus spp.) and kangaroo mice (Microdipodops spp.) is among the most studied aspect of this family's biology. Brown and Harney (1993) provide a comprehensive overview and attempted synthesis of this complex subject. Presented here are some generalizations that fall from this large body of literature.
Arid grassland and generally xeric habitats (including the coastal sage scrub and chaparral communities in southern California) support a surprising diversity of coexisting rodent granivores. The diversity and number of coexisting species varies depending on local conditions and the requirements of the constituent species. For example, the Dulzura kangaroo rat in Riverside County is known to overlap with three other kangaroo rats species or subspecies, (D. stephensi, D. merriami collinus and D. merriami parvus), possibly the Pacific kangaroo rat, possibly three pocket mice (Chaetodipus fallax, C. californicus, and Perognathus longimembris), and at least four murids (Peromyscus maniculatus, P. eremicus, Neotoma lepida, and Reithrodontomys megalotis) that would compete for space and food resources. Brown and Harney (1993) conclude that "the composition of these assemblages is not random. Instead it is determined by interactions of the species with the physical environment, with other kinds of organisms, and with other rodent species." page 646. Generally, species that do coexist tend to occupy and exploit different microhabitats or niches or differ in their seasonality of resource exploitation.
Interspecific competition is an important component of the organization of heteromyid community structure. For example, competitive exclusion can result in nonrandom assemblages that partition the resources and habitats in the community. Other potential mechanisms of resource partitioning listed by Brown and Harney (1993) include habitat selection or restriction, independent adaptations, food partitioning and variable foraging efficiency, seed distribution, resource variability, predator-mediated coexistence, aggressive interference, and seasonality.
Studies by Price and her colleagues (Price et al. 199l; Price and Goldengay 1992; Goldengay and Price 1997) directly address the relationship between the Dulzura kangaroo rat and the sympatric congener Stephens' kangaroo rat. They clearly demonstrated that in areas where the Stephens' kangaroo rat and Dulzura kangaroo rat overlap, the Dulzura kangaroo rat was captured in areas with significantly greater shrub and rockier cover than the Stephens' kangaroo rat. Price et al. (1991) demonstrated that Dulzura kangaroo rats forage under shrub canopies and avoid lighted open areas more than Stephens' kangaroo rat. In a consistent pattern, the Stephens' kangaroo rat also appears to be socially dominant over the Dulzura kangaroo rat (Bleich and Price 1995) and may actively exclude them from grassland habitat. In the absence of the Stephens' kangaroo rat, Dulzura kangaroo rats often occur in grasslands that are near chaparral or coastal sage scrub (Behrends, pers. obs.); perhaps an example of "ecological release" in the absence of a direct competitor. Also, Price and Waser (1984) found that Dulzura kangaroo rats increase in abundance following wildfires that create openings in chaparral and sage scrub habitats, so it is clear that they use open habitats when provided the opportunity.
Kangaroo rats and other heteromyid rodents also modify their environments (Brown and Harney 1993). They dig burrows, which moves the soils and provides habitat and refugia for other species, including other rodents, reptiles, amphibians, birds and invertebrates. Collection, storage and consumption of seeds by kangaroo rats has profound effects on the vegetation structure of the habitats they occupy. For example, experiments by Brown and his colleagues in southeastern Arizona have demonstrated that kangaroo rats are a "keystone guild" where their removal from plots resulted in the habitat converting from desert shrub to grassland (Brown and Heske 1990). In addition, resource use by kangaroo rats substantially overlaps with that of seed-eating birds and harvester ants. Where kangaroo rats have been excluded in experimental plots, ants have increased dramatically (Brown and Harney 1993).
The coevolutionary results of such inter- and intraspecific community relationships and their relationship to plant communities are not understood, but it can be concluded that rodents are an important component of arid ecosystems. In addition to their direct impacts on plant communities, they are important prey for a variety of predators and their presence also affects populations of other prey such as small reptiles, lagomorphs and some birds (Brown and Harney 1993).
Physiological Ecology: Kangaroo rats and most other heteromyid species live in arid environments characterized by hot summers, long, cold winters, unpredictable precipitation, and ephemeral primary productivity of food sources (French 1993). For example, D. merriami have been observed on the surface at temperatures of -19 degrees Celsius (Kenagy 1993). Living in such extreme environmental conditions has high metabolic and thermoregulatory costs.
Kangaroo rats are perhaps most famous for their water conservation capabilities. Schmidt-Nielsen (1964) and French (1993) summarized the behavioral and physiological means by which kangaroo rats conserve water: they occupy burrows during daylight hours to avoid high temperatures; their evaporative water loss is much lower than other mammals when corrected for body mass; they have relatively low metabolic rates (about 30 percent lower than average mammals); they produce low volumes of highly concentrated urine and low moisture feces; and their water requirements may be satisfied by oxidative or metabolic water in conjunction with the seeds and herbaceous material they consume. The Dulzura kangaroo rat, which inhabits relatively mesic environments compared many other heteromyid species, however, cannot survive without preformed (exogenous) water and does not thrive well on a seed only diet; they need free water or succulent vegetation to thrive in laboratory conditions (Forman and Phillips 1993; French 1993).
The Dulzura kangaroo rat is still common in coastal sage scrub, chaparral and shrub-grassland ecotones below about 2,600 feet. As with most kangaroo rat species, it is probably more common in habitats with sparse vegetation, as density of vegetation affects the burrowing, locomotion and foraging ability of kangaroo rats. Periodic fires or temporary clearing of habitats appears to facilitate colonization by this species (Price and Waser 1984; Price et al. 1995). However, specific habitat management probably is not required to sustain this species in the Plan Area.
Habitat Loss: The greatest potential threat to the Dulzura kangaroo rat is habitat loss and fragmentation.
Disease: The relationship of parasites and associates (e.g., viruses, bacteria, spirochetes, fungi, protozoa, etc.) in disease in D. simulans is not well understood, but various studies summarized by Whitaker et al. (1993) indicate that the species supports and/or may be affected by a variety of organisms (note: the data reported here are for D. agilis so it can only be assumed that recorded parasites could occur in D. simulans as well). While many of these "parasites" may be benign, others may cause disease and mortality that could have severe impacts on small, insular populations. Because of the large number of parasites and associates likely found on D. simulans, only a brief summary of the general types and number of genera and species are reported here. The reader is directed to Whitaker et al. (1993) for a more detailed description.
D. simulans may carry at least eight species of protozoa, seven species of chiggers, two species hard ticks, and one species of flea. The effects of these parasites and their associates on the health of D. simulans generally are unknown. Many may be benign, but some may be pathogenic and have deleterious effects on populations (Whitaker et al. 1993). Such effects in small, isolated populations would be particularly serious. The relationships between host and parasites, such whether they cause harm to the host, the geographic range of the parasites, and whether the number of parasites an individual carries is related to health, are all topics that require further study (Whitaker et al.1993).
Best, T.L, R.M. Sullivan, J.A. Cook, and T.L. Yates. 1986. Chromosomal, genic, and morphological variation in the agile kangaroo rat, Dipodomys agilis (Rodentia: Heteromyidae). Systematic Zoology 35:311-324.
Bleich, V.C. and M.V. Price. 1995. Aggressive behavior of Dipodomys stephensi, and endangered species, and Dipodomys agilis, a sympatric cogener. Journal of Mammalogy 76:646-651.
Bolger, D.T., A.C. Alberts, R.M. Sauvajot, P. Potenza, C. McCalvin, D. Tran, S. Mazzoni, and M.E. Soulé. 1997. Responses of rodents to habitat fragmentation in coastal southern California. Ecological Applications 7:552-563.
Brown, J.H. and B.A. Harney. 1993. Population and community ecology of heteromyid rodents in temperate habitats. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No, 10 of the American Society of Mammalogists, pages 618-651.
Brown, J.H. and E.J. Heske. 1990. Mediation of a desert-grassland transition by a keystone rodent guild. Science 250:1705-1707.
Daly, M. M.I. Wilson, and P. Behrends. 1984. Breeding of captive kangaroo rats, Dipodomys merriami and D. microps. Journal of Mammalogy 65:338-341.
Eisenberg, J.F. 1993. Ontogeny. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 479-490.
Forman, G.L. and C.J. Phillips. 1993. The proximal colon of heteromyid rodents: possible morphophysiological correlates to enhanced water conservation. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No.10 of the American Society of Mammalogists, pages 491-508.
French, A.R. 1993. Physiological ecology of the Heteromyidae: economics of energy and energy and water utilization. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 509-538.
Goldingay, R.L. and M.V. Price. 1997. Influence of season and a sympatric cogener on habitat use by Stephens' kangaroo rat. Conservation Biology 11:708-717.
Jones, T. 1993. Social systems of heteromyid rodents. In Genoways, H.H. and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10, The American Society of Mammalogists, pp. 575-595.
Kenagy, G.J. 1973. Daily and seasonal patterns of activity and energetics in a heteromyid community. Ecology 54:1201-1219.
MacMillen, R.E. 1964. Population ecology, water relations, and social behavior of a southern California semidesert rodent fauna. University of California Publications in Zoology 71:1-59.
McCloskey, R.T. 1972. Temporal changes in populations and species diversity in a California rodent community. Journal of Mammalogy 53:657-676.
Patton, J.L. and D.S. Rogers. 1993. Cytogenics. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No, 10 of the American Society of Mammalogists, pages 236-258.
Price, M.V., P.A. Kelly, and R.L. Goldingay. 1994. Distances moved by Stephens' kangaroo rat (Dipodomys stephensi) and implications for conservation. Journal of Mammalogy 75:929-939.
Price, M.V. and Goldengay. 1992. Final Report: Part D. Temporal stability of space use by Dipodomys stephensi and D. agilis in a habitat mosaic. Submitted to the Riverside County Habitat Conservation Agency, 36 pp.
Price, M.V. and N.M. Waser. 1984. On the relative abundance of species: postfire changes in a coastal sage scrub rodent community. Ecology 65:1161-1169.
Price, M.V., N.M Waser, K.E. Taylor and K.L. Pluff. 1995. Fire as a management tool for Stephens' kangaroo rat and other small mammal species. In J.E. Keely and T. Scott (eds.) Brushfires in California Wildlands: Ecology and Resource Management, International Association of Wildland Fire, Fairfield, WA. pp. 51-61.
Price, M.V., W.S. Longland, and R.L. Goldengay, 1991. Niche relationships of Dipodomys agilis and Dipodomys stephensi: two sympatric kangaroo rats of similar size. American Midland Naturalist 126:172-186.
Randall, J.A. 1993. Behavioural adaptations of desert rodents (Heteromyidae). Animal Behaviour 45:263-287.
Schmidt-Nielsen, K. 1964. Desert Animals, Oxford University Press, London, 277 pp.
Smith, H.D. and C.D. Jorgensen. 1975. Reproductive biology of the North American desert rodents. In I. Prakash and P.K. Ghosh (eds.) Rodents in Desert Environments, The Hague: W. Junk, pp 305-330.
Sullivan, R.M. and T.L. Best. 1997. Systematics and morphological variation in two chromosomal forms of the agile kangaroo rat (Dipodomys agilis). Journal of Mammalogy 78:775-797.
Whitaker, J.O. Jr., W.J. Wrenn, and R.E. Lewis. 1993. Parasites. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 386-478.
Williams, D.F., H.H. Genoways, and J.K. Braun. 1993. Taxonomy. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 38-196.
Wilson, D.E. and S. Ruff (eds.). 1999. The Smithsonian Book of North American Mammals. The Smithsonian Institution in association with the American Society of Mammalogists, 750 pp.
long-tailed weasel (Mustela frenata)
State: None
Federal: None
The long-tailed weasel occurs throughout the Plan Area in virtually all types of habitat, including agricultural and disturbed areas. It may occur wherever there is sufficient prey. However, the weasel population levels in the Plan Area are unknown and additional study is needed to identify possible Core Areas and basic life history requirements of the species. Baseline study and monitoring of weasels in the MSHCP Conservation Area, therefore, will be key factors for conservation of this species.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 474,500 acres (49 percent) of suitable habitat in the Plan Area. Conservation in the primary core habitat areas includes the Existing Core A (10,740 acres), Existing Core B (71,490 acres contiguous with Cleveland National Forest in Orange County), Existing Core C (15,610 acres), Existing Core F (8,360 acres), Existing Core G (4,490 acres), Existing Core H (17,470 acres), Existing Core I (9,610 acres contiguous with San Bernardino National Forest in San Bernardino County), Existing Core J (24,370 acres), Existing Core K (149,750 acres), Existing Core L (24,750 acres contiguous with Cleveland National Forest in San Diego County), Existing Core M (10,460 acres contiguous with Cleveland National Forest in San Diego County), Proposed Core 1 (7,470 acres), Proposed Core 2 (5,050 acres), Proposed Core 3 (24,920 acres), Proposed Core 4 (11,890 acres), Proposed Core 5 (3,220 acres), Proposed Core 6 (4,290 acres), and Proposed Core 7 (50,000 acres).
Include within MSHCP Conservation Area approximately 52,400 acres of dispersal and/or movement linkages between core habitat blocks. Given the mobility of the long-tailed weasel and its use of drainages and agricultural areas, it potentially could use all the identified unconstrained and constrained linkages in the MSHCP Conservation Area.
Within the MSHCP Conservation Area, maintain (once every 8 years) the continued use of long-tailed weasel at a minimum of 75 percent of the localities where the species has been known to occur.
The MSHCP database for the long-tailed weasel is scant and only provides distributional information. However, because long-tailed weasels occur throughout the Plan Area in virtually all types of natural and some altered habitats, the conservation analysis primarily is conducted at the landscape level.
For the purpose of the conservation analysis, suitable habitat for the long-tailed weasel includes all natural habitats and agriculture, excluding desert scrubs and open water. Desert scrubs may be too dry for the weasel, which only is absent from desert regions in the American southwest. Based on this habitat assumption, the Plan Area contains approximately 965,187 acres of suitable habitat for the weasel. Table 1 shows the conservation of suitable habitat for the long-tailed weasel. Overall, approximately 474,500 acres (49 percent) of suitable habitat in the Plan Area would be conserved in the MSHCP Conservation Area.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
LONG-TAILED WEASEL
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Agricultural Land | 168,363 | 8,542 | 11,482 | 20,024 | 7,319 | 141,020 | 148,339 |
| Chaparral | 413,488 | 64,899 | 207,831 | 272,280 | 59,582 | 81,626 | 141,208 |
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,970 |
| Grassland | 146,869 | 20,011 | 22,806 | 42,817 | 12,223 | 91,829 | 104,052 |
| Meadow | 492 | 0 | 87 | 87 | 18 | 387 | 405 |
| Meadow and Marshes | 470 | 174 | 239 | 413 | 0 | 57 | 57 |
| Montane Coniferous Forest | 29,900 | 17 | 20,845 | 20,502 | 43 | 9,355 | 9,398 |
| Peninsular Juniper Woodland and Scrub | 1,082 | 336 | 274 | 609 | 23 | 450 | 473 |
| Playas and Vernal Pools | 7,914 | 3,828 | 2,923 | 6,751 | 0 | 1,163 | 1,163 |
| Riparian Scrub, Woodland and Forest | 4,607 | 3,920 | 7,273 | 1,193 | 368 | 3,045 | 3,413 |
| Riversidean Alluvial Fan Sage Scrub | 7,148 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,914 |
| Woodlands and Forest | 32,168 | 2,388 | 20,497 | 22,885 | 5,017 | 4,266 | 9,283 |
| TOTAL | 965,187 | 154,448 16% |
330,875 34% |
474,511 49% |
111,051 11% |
379,624 39% |
490,675 51% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Known current and historic locations of long-tailed weasels that are in the MSHCP Conservation Area include San Jacinto Wildlife Area, the Badlands, San Timoteo Creek, Lake Skinner-Diamond Valley Lake, Alberhill, Warm Springs Creek, and Tahquitz Valley in the San Jacinto Mountains. They also probably occur in other large habitats areas that will be in the reserve, including Lake Mathews-Estelle Mountain, Santa Ana River-Prado Basin, Santa Rosa Plateau-San Jacinto Mountains, Agua Tibia Wilderness-Palomar Mountains, Vail Lake-Sage-Aguanga, and the Anza-Cahuilla valleys.
Smaller habitat areas that probably would be isolated from the larger habitat complexes are the Jurupa Mountains, Box Springs Mountain, Lakeview Mountains, Sycamore Canyon Regional Park, Norco Hills, Double Butte, and Motte-Rimrock Reserve, although agriculture adjacent to these areas may provide habitat for weasels in the immediate future. If these areas become permanently isolated by urban development as the region is built out, weasels may be extirpated from some of these areas. As noted below in the Species Account, weasels may be susceptible to local extinctions when prey levels drop.
Habitat connections between large habitat blocks will be important for conservation of the long-tailed weasel. Waterways, drainages and riparian areas are thought to be important for dispersal, especially in areas where the adjacent habitat may be unsuitable (Fagerstone 1987). However, nothing is known about the relationship between populations of long-tailed weasels in different parts of the Plan Area (e.g., immigration and emigration patterns) and no general species data on dispersal were found in the literature. Home range studies, however, show that weasels are capable of moving great distances when prey are scarce, with ranges as large as 160 ha (395 acres) recorded (cited in Sheffield and Thomas 1997). Given the existing distribution of suitable habitat, reserve configuration, and their ability to move long distances along narrow habitat connections, weasels conceivably could move throughout the Plan Area. Certainly the area defined by the Badlands in the north and the Vail Lake-Agua Tibia Wilderness in the south provides contiguous suitable habitat, with the only barriers to movement the major roads in the area, including Highway 60 and Highway 79 (Lamb Canyon Road) through the Badlands, Highway 74 east of Hemet and Highway 79 between Vail Lake and Aguanga. Male weasels apparently attempt to cross roads frequently and road kills are elevated during the breeding season when males are roaming in search of mates (Buchanan 1987). The Santa Rosa Plateau-Santa Ana Mountains is connected to Lake Mathews-Estelle Mountain along Indian Canyon and Horsethief Canyon and to the Agua Tibia Wilderness along Pechanga Creek. Constrained linkages (i.e., long connections bounded by unsuitable habitat) that may limit use by weasels include Murrieta Creek, Warm Springs Creek, and Temecula Creek. The San Jacinto River provides a connection along the base of the Badlands to San Jacinto Wildlife Area-Lake Perris, and possibly to the Kabian area farther to the south. Habitat in the western portion of the Plan Area mainly would be connected by the Santa Ana River.
In summary, conservation for this species will be achieved by inclusion of at least 474,500 acres (49 percent) of the suitable Conserved Habitat and conservation of linkages between large habitat areas.
Approximately 490,675 acres (51 percent) of suitable habitat for the long-tailed weasel will not be conserved.
The MSHCP database for the long-tailed weasel is sparse. There are only 27 records for the species in western Riverside County. Of the 27 records, five are precision code "1" (an "x' and "y" coordinate that allows for good precision in the location), eight are precision code "2" (an "x" or "y" coordinate or equivalent), and the remaining 14 are precision codes "3" or "4" (relatively imprecise locations from general areas). Nine of the records date from 1990, 14 from between 1968 and 1989 and three from 1889-1939. One record has no associated date. The code 1 and 2 records date from 1974. Other than providing general distributional information, the data points are not very useful for conservation planning.
The long-tailed weasel prefers habitats with abundant prey, such as those areas where dens of burrowing rodents are numerous and close to cover and areas supporting large populations of small mammals and birds (Polderboer et al. 1941). Prey species diversity probably is an important factor in determining suitable habitat for this species. The long-tailed weasel also appears to be partially restricted to habitats in close proximity to standing water (Gamble 1981). Waterways provide access to suitable habitat and are natural avenues for dispersal, particularly in areas that otherwise are unsuitable (Fagerstone 1987). Preferred habitat types include brushland and open timber, brushy field borders, grasslands along creeks and lakes, and swamps (Svendsen 1982). Dens are located in dense-brushy vegetation in, or bordering, dry creeks or ravines.
In Western Riverside County, the MSHCP database includes two records in chaparral, four in crop lands, two in non-native grassland, three in Riversidean sage scrub, one in coniferous forest, and one in alkali playa. Eleven records are in areas mapped as residential/urban/exotic, with the most recent record from 1993. Records for this species in areas mapped as residential/urban/exotic is not surprising because weasels often are found in rural areas near agriculture.
The species M. frenata has the largest range of any mustelid in the western hemisphere, and, except for deserts, inhabits most life zones from alpine to tropical. It occurs in all 48 contiguous states (Hall 1981; Sheffield and Thomas 1997). However, the subspecies M. f. latirostra occurs in a very small area of southern California, primarily in portions of eastern Orange County, western Riverside County and northern San Diego County (Hall 1981).
Known current and historic locations of long-tailed weasels include Moreno Valley, San Jacinto Wildlife Area, the Badlands, San Timoteo Creek, Beaumont, Riverside, Pedley, Cherry Valley, Cabazon, Norco, the San Jacinto Plain, Lake Skinner, Crown Valley, Lake Elsinore/Alberhill, Warm Springs Creek, Temecula and Tahquitz Valley in the San Jacinto Mountains. They probably occur throughout western Riverside County in areas of large open space where diverse prey are available.
The long-tailed weasel occurs in low population densities throughout the Plan Area. No particular area stands out as supporting greater populations or the highest quality habitat.
Most of the information below is from the species account for the long-tailed weasel prepared by Sheffield and Howard (1997). Other literature is cited where relevant.
Genetics: The diploid number of chromosomes of the long-tailed weasel is 42. As of 1977, no electrophoretic or molecular genetic data were available
Diet and Foraging: Long-tailed weasels feed mostly on rodents and other small mammals and will attack animals larger than themselves. Predatory behavior consists of hunting, pursuing, attacking and killing prey. They are highly mobile and have been observed to hunt in burrows for rodents, tunnel under snow in the winter, and climb trees for prey (climbing may also be an anti-predator strategy). Trees also may be used for caching food during the winter months (Weeks 1993). While they are highly opportunistic foragers, primary prey of weasels consist of voles (Microtus spp., Clethrionomys gapperi) and deer mice (Peromyscus spp.), with less common prey being grasshopper mice (Onychomys spp.), harvest mice (Reithrodontomys megalotis), woodrats (Neotoma spp.), cotton rats (Sigmodon spp.), bog lemmings (Synaptomys spp.), muskrats (Ondatra zibethicus), meadow jumping mice (Zapus hudsonius), house mice (Mus musculus), pocket gophers (Thomomys spp, Geomys spp., Cratogeomys spp.), ground squirrels (Spermophilus spp.), chipmunks (Tamias spp.), red squirrels (Tamiasciuris hudsonicus), gray squirrels (Sciurus carolinensis), fox squirrels (Sciurus niger), flying squirrels (Glaucomys spp.), and mountain beavers (Aplodontia rufa). They also have been observed chasing the endangered Stephens' kangaroo rat (Dipodomys stephensi) in the Banning area, but no kills were observed (P. Behrends and R. Baxter, pers. obs.). Lagomorphs (hares and rabbits), birds (including eggs and poultry), and rarely snakes and lizards, also are taken by the long-tailed weasel. Weasels also have been observed to feed on carrion. Because they feed on poultry, weasels are considered an agricultural pest species in some areas.
Daily Activities: The long-tailed weasel primarily is nocturnal, but may be active anytime of the day (Sheffield and Thomas 1997; P. Behrends, pers. obs.).
Reproduction: The breeding season of the long-tailed weasel is variable. Some females enter estrus in the late spring and summer (39-104 days postpartum) and others are estrous as early as mid-March. Males are reproductive as early as February and as late as December. The breeding season in northern latitudes is shorter, with cessation of male reproductive activity by September. Weasels exhibit delayed implantation of the fertilized eggs of about 68 to 250 days. Gestation, including the implantation period, ranges from 205-337 days, with an average of 279 days. Females produce one little per year of 3-9 offspring (average of 4-5) born between mid-April and early May. Lactation lasts approximately five weeks. Females may breed in early in the summer of their natal year with males that reside within the range of the female's mother. However, because of high male turnover, the male probably is not the one that bred with their mother (i.e., the female's father). Males first breed at about 15 months of age. Males may provide caretaking of offspring.
Although populations of the long-tailed weasel appear to be more stable than other weasel species (M. erminea and M. nivalis), they also fluctuate and local populations may be extirpated in response to changes in the abundance of prey (King 1989 as cited by Sheffield and Thomas 1997).
Survival: No data were found on survival and mortality rates. However, it was noted by Sheffield and Thomas (1997) that male turnover is very high. Svendsen (1982) listed five sources of natural mortality in weasels: disease, parasites (see below), nutrition, population stress, and predation. Long-tailed weasels are prey for a number of predators. Their primary predators are red fox (Vulpes vulpes) and gray fox (Urocyon cinereoargenteus). Other predators are raptors (Owls and hawks), coyotes (Canis latrans), martens (Martes americana), bobcats (Lynx rufus), rattlesnakes (Crotalus spp.) and domestic cats (Felis cattus) and dogs (Canis lupus familiaris). Other sources of mortality include trapping, shooting, road kills, and the Powassan virus. Interestingly, Buchanan (1987) noted that of 17 road kills, all were males, including two juveniles, and all road kills were found between April 29 and August 17, or roughly during the breeding season.
Dispersal: No data regarding long-tailed weasel dispersal behavior were found.
Socio-Spatial Behavior: Long-tailed weasels are solitary most of the year, but home ranges of males and females overlap and males may remain with females during the non-breeding season. Male-male home ranges do not overlap. Home ranges may vary by season and male home ranges are larger than female ranges. In Kentucky, for example, summer home ranges ranged from 16 to 24 ha and winter ranges ranged from 10 to 18 ha. Where prey are scarce home ranges as large as 160 ha have been recorded. During the breeding season, male ranges increase in size to overlap those of more females. Increased road kill of males has been observed in western Washington during the breeding season, indicating higher levels of roaming in search of mates (Buchanan 1987).
Population densities of long-tailed weasels are difficult to census because of their low densities and distribution related to habitat characteristics and prey densities. Densities of 0.004 to 0.008 weasels/ha have been reported in Colorado, 0.19 to 0.38/ha in chestnut oak forest and 0.07 to 0.09/ha in scrub oak in Pennsylvania, and 0.2 to 0.3/ha in cattail marsh in Ontario, Canada.
Community Relationships: No information was found regarding community relationships. This species forages on a number of small mammals, birds, and reptiles, but little is known of these dynamics. The weasel is prey for a number of species of birds, canids, and snakes, but its importance in their diet is unknown. Given the low population densities of weasels, it seems unlikely that they would be a primary prey for any species.
Physiological Ecology: The long-tailed weasel has a long, slender body shape, and when resting it is in a flattened, disk-like and coiled posture, resulting in a relatively high exposed surface area (Sheffield and Thomas 1997). As a result, it has a relatively high metabolic rate and mass-specific rate of heat loss. Their food requirements are, for example, 1.5 voles/day, or about 17-33 percent of their body weight. It has been suggested that smaller winter ranges allow the weasel to conserve energy used for thermoregulation. Furthermore, weasels have been observed to cache food in trees during the winter, and it has been suggested that such caching functions meet additional energy needs during cold periods (Weeks 1993).
Habitat Loss: Virtually nothing is known of the population trends of weasels in the MSHCP Plan Area, but it can be expected that without a reserve system the species would eventually be threatened with habitat loss and fragmentation, and potential genetic isolation. Maintaining patches of habitat that support abundant prey species and riparian strips and unimpeded drainages probably are important for this species.
Disease: The Powassan virus is a source of mortality. Ectoparasites include several species of fleas, sucking louse, biting lice, ticks, chiggers, and mites. Endoparasites include trematodes (a fluke or flatworm) and nematodes (roundworms). Weasels have also tested positive for plague.
Because of their generalist habits, long-tailed weasel populations throughout their range are considered to be relatively stable, but they show fluctuations and may become locally extinct in relation to prey availability. In Alberta, Canada, for example, weasels exhibited a 10-year cycle in relation to snowshoe hare populations.
Special consideration for conservation of weasels includes conservation of riparian areas for dispersal linkages, conservation of microhabitats such as rock outcrops and logs for dens, and control of artificial lighting near reserves which may affect nocturnal activities.
Bolger, D.T., A.C. Alberts, R.M. Sauvajot, P. Potenza, C. McCalvin, D. Tran, S. Mazzoni, and M.E. Soulé. 1997. Responses of rodents to habitat fragmentation in coastal southern California. Ecological Applications 7:552-563.
Buchanan, J.B. 1987. Seasonality in the occurrence of the long-tailed weasel road-kills. The Murrelet 68:67-68.
Fagerstone, K.A. 1987. Black-footed ferret, long-tailed weasel, short-tailed weasel, and least weasel. Pp. 549-573, in M. Novak, J.A. Baker, M.E. Obbard and B. Malloch (eds.) Wild Furbearer Management and Conservation in North America. Ontario Ministry of Natural Resources, Toronto, Ontario. 1150 pp.
Gamble, R. L. 1981. Distribution in Manitoba of Mustela frenata longicauda, the long-tailed weasel, and the interrelation of distribution and habitat selection in Manitoba, Saskatchewan, and Alberta. Canadian Journal of Zoology 59:1036-1039.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Murie, O.J. 1974. A Field Guide to Animal Tracks. The Peterson Field Guide Series. Houghton Mifflin, Company, Boston.
Polderboer, E.B., L.W. Kuhn, and G.O. Hendrickson. 1941. Winter and spring habits of weasels in central Iowa. Journal of Wildlife Management 5:115-119.
RIC. 1998. Inventory methods for martens and weasels. Standards for Componenets [sic] of B.C.'s Biodiversity, No. 24. Prepare by the Ministry of Environment, Lands and Parks, Resources Inventory Branch for the Terrestrial Ecosystems Task Force, Resources Inventory Committee. <www.for.gov.ca/RIC/Pubs/teBioDiv/marten/>
Sheffield, S.R. and H. H. Thomas. 1997. Mustela frenata. In: Mammalian Species 570:1-9, published by the American Society of Mammalogists.
Svendsen, G.E. 1982. Weasels, Mustela species. Pages 613 - 628, in: J. Chapman and G.A. Feldhamer, (eds.), Wild Mammals of North America, Johns Hopkins University Press, Baltimore.
Weeks, H.P. Jr. 1993. Arboreal food caching by long-tailed weasels. Prairie Naturalist 25:39-42.
Los Angeles pocket mouse (Perognathus longimembris brevinasus)
State: Species of Special Concern
Federal: None
The Los Angeles pocket mouse generally is widely distributed in the eastern two-thirds of the Plan Area, but recent known localities are sparsely scattered throughout this area. This species appears to be limited to sparsely vegetated habitat areas in patches of fine sandy soils associated with washes or of aeolian (windblown ) origin, such as dunes. The current status of populations in the Plan Area is unknown, but some biologists believe that the Los Angeles pocket mouse is in serious decline in the region because it is seldom trapped and much of its suitable habitat has been lost to agriculture and urban development. Conservation of sage scrub and grassland habitats on sandy soils, population monitoring and adaptive management will be important for this species. The Los Angeles pocket mouse is considered a Group 3 species because of its scattered distribution in the Plan Area, association with specific micro-habitats, a lack of information about existing populations, and the need for population monitoring and adaptive management.
The Los Angeles pocket mouse is on the Additional Survey Needs and Procedures (Section 6.3.2) list and surveys for the species will be conducted as part of the project review process for public and private projects within the mammal species survey area where suitable habitat is present (see Mammal Species Survey Area Map, Figure 6-5 of the MSHCP, Volume I). Los Angeles pocket mouse localities found as a result of survey efforts shall be conserved in accordance with the procedures described within Section 6.3.2, MSHCP, Volume 1.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area, at least 14,000 acres of suitable habitat for the Los Angeles pocket mouse (e.g., sandy to loamy-sand soils occurring in non-native grassland, Riversidean sage scrub, Riversidean alluvial fan sage scrub, desert scrub, playa and vernal pool, chaparral, or redshank chaparral habitat), with at least 2,000 acres within each of seven (7) Core Areas within the MSHCP Conservation Area. Based on existing population distribution information, probable Core Areas include the following: 1) San Jacinto Wildlife Area-Lake Perris Reserve, 2) the Badlands, 3) San Jacinto River and Bautista Creek, 4) Anza Valley, 5) Lake Skinner-Domenigoni Reserve, 6) Potrero Valley, and 7) Temecula Creek.
Include within the MSHCP Conservation Area at least 10,000 acres of suitable habitat for the Los Angeles pocket mouse outside of the probable Core Areas identified above, but within the Criteria Area. Criteria Area locations where additional habitat likely will be conserved include the Santa Ana River (northeast of Highway 60 and possibly in some areas downstream), Wilson Creek, Vail Lake, Warm Springs Creek, San Timoteo Creek, and San Gorgonio Wash.
Surveys for Los Angeles pocket mouse will be conducted as part of the project review process for public and private projects within the mammal species survey area where suitable habitat is present (see Mammal Species Survey Area Map, Figure 6-5 of the MSHCP, Volume I). Los Angeles pocket mice located as a result of survey efforts shall be conserved in accordance with the procedures described in Section 6.3.2 of the MSHCP, Volume 1.
Survey and site-specific conservation efforts will continue until there is a minimum of seven Core Areas with at least 2,000 acres of suitable habitat within each core area, for a total of 14,000 acres of suitable habitat.
Within the MSHCP Conservation Area, Reserve Managers shall demonstrate that each of the seven Core Areas supports a stable or increasing population that occupies at least 30 percent of the suitable habitat (at least 4,200 acres) as measured over any 8-consecutive year period (i.e., the approximate length of the weather cycle).
The Los Angeles pocket mouse probably occurs in a patchy distribution in relation to soils and habitat conditions. Although it is geographically widespread in the Plan Area, it is not common. The conservation analysis considers the patchy nature of this species and the habitat characteristics thought to be important for its occurrence. For this conservation analysis, it is assumed that the Los Angeles pocket mouse primarily occurs in drainages with sandy soils associated with the following habitats: chaparral, coastal sage scrub (Riversidean sage scrub, Riversidean alluvial fan sage scrub, and Diegan coastal sage scrub), desert scrub, grassland, and vernal pools and playas. Because the pocket mouse has not been documented in the southwestern portion of the Plan Area, several major drainages that otherwise appear to support suitable habitat were omitted from the estimate of suitable habitat, including the Santa Ana River south of Highway 60, Temescal Wash, Murrieta Creek, and Temecula Creek west of Vail Lake. If future field studies document the Los Angeles pocket mouse in any of these drainages, the estimates of conserved habitat would need to be revised.
Based on these assumptions about suitable habitat, the Plan Area supports at least 52,000 acres of suitable habitat for the Los Angeles pocket mouse. Table 1 shows the conservation of suitable habitat for the Los Angeles pocket mouse. Overall, approximately 32,581 acres (62 percent) of suitable habitat in the Plan Area would in the MSHCP Conservation Area.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
LOS ANGELES POCKET MOUSE
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 10,871 | 5,434 | 913 | 6,347 | 1,359 | 3,165 | 4,524 |
| Riversidean Sage Scrub | 10,846 | 3,148 | 4,172 | 7,320 | 1,264 | 2,262 | 3,526 |
| Desert Scrub | 1,477 | 893 | 37 | 930 | 0 | 547 | 547 |
| Riversidean Alluvial Fan Sage Scrub | 3,879 | 1,809 | 1,400 | 3,209 | 22 | 648 | 670 |
| Playas and Vernal Pools | 6,192 | 2,932 | 2,849 | 5,781 | 0 | 411 | 411 |
| Grassland | 18,824 | 4,629 | 4,365 | 8,994 | 722 | 9,108 | 9,830 |
| TOTAL | 52,089 | 18,845 36% |
13,736 26% |
32,581 62% |
33,676 6% |
16,141 31% |
19,508 37% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Several Core Areas known to support the Los Angeles pocket mouse are in the MSHCP Conservation Area and will be conserved. These areas include two of the existing Stephens' kangaroo rat core reserves (San Jacinto Wildlife Area-Lake Perris and Lake Skinner-Diamond Valley Lake), and two new core reserves (Potrero Valley and Silverado Ranch Conservation Bank in the Anza Valley). Additional important known occupied and suitable habitat areas that would be in the MSHCP Conservation Area include the San Jacinto River between Interstate 215 and the National Forest, Bautista Creek south from the dam, portions of the Badlands (including Potrero Valley and Reche Canyon), Temecula Creek between Aguanga and Vail Lake, Tucalota Creek east of Lake Skinner, Tule Valley, Wilson Creek, Vail Lake, Warm Springs Creek, Cactus Valley, San Timoteo Creek, and San Gorgonio Wash. Although no records are known from the Santa Ana River, it is possible that the Los Angeles pocket mouse occurs in the river northeast of Highway 60 and possibly in some areas downstream.
Because the Los Angeles pocket mouse inhabits intermittent washes, it would be afforded some additional protection through MSHCP policies to protect wetland habitats and species, as described in Section 6.1.2. Also, the Los Angeles pocket mouse may receive some protection in conjunction with conservation for the federally-listed endangered Delhi sands flower-loving fly in the northwest portion of the Plan Area around the Jurupa Mountains. Sandy soils of aeolian origin preserved in this area also have high potential for the Los Angeles pocket mouse.
Connections between core habitat areas for this species will be important. Fortunately this species inhabits intermittent sandy washes and drainages that provide natural habitat connections, as long as they are not highly modified for flood control or other activities such as dry land farming or sand and gravel extraction. Existing information indicates that the species P. longimembris is relatively sedentary and shows high site fidelity (Chew and Butterworth 1964; Spencer and Schaefer 2000), so having suitable permanent habitat within habitat connections will be important for maintaining the exchange of individuals and genetic material between core populations.
The Plan Area includes two important habitat complexes for the Los Angeles pocket mouse that would be fairly well connected.
The San Jacinto Wildlife Area-Lake Perris-Badlands-San Jacinto River complex includes other important discrete pocket mouse locations, including Reche Canyon, Potrero Valley, and San Timoteo Creek. This habitat complex generally is contiguous, with the exception of four major roads: Gilman Springs Road between the San Jacinto Wildlife Area and the Badlands; Highway 79 between the northwestern portion of the Badlands and Potrero Valley; Highway 60 which bisects the Badlands; and Redlands Boulevard which also bisects the Badlands farther to the west. Construction of adequate culverts below some these roads may be needed to allow for pocket mouse movement within these areas.
The Lake Skinner-Diamond Valley Lake-Sage-Wilson Valley-Vail Lake-Aguanga-Anza Valley complex also provides a large, relatively contiguous habitat complex for the Los Angeles pocket mouse. Potential obstacles to movement between these areas are Sage Road, Highway 79 (between Temecula and Aguanga), and Highway 371. However, the rural character of this region will be preserved and it is expected that existing habitat connection function also will be preserved.
In summary, conservation of the Los Angeles pocket mouse will be achieved by inclusion of approximately 32,581 acres (62 percent) of suitable Conserved Habitat in the MSHCP Conservation Area. Although the size and extent of existing populations of the Los Angeles pocket mouse in the Plan Area is unknown, based on distribution records, the probable key population areas are reasonably well understood. Several of these key areas would be in the MSHCP Conservation Area, including San Jacinto Wildlife Area-Lake Perris, Lake Skinner-Diamond Valley Lake, Potrero Valley, and Silverado Ranch Conservation Bank in the Anza Valley. Additional important known habitat areas that would be conserved include the San Jacinto River in the Hemet-Valle Vista area and San Jacinto Wildlife Area, Bautista Creek, Temecula Creek between Aguanga and Vail Lake, portions of the Badlands, and Reche Canyon. With perhaps the exception of populations in the Temecula-Murrieta area, it seems unlikely that additional key populations would not be conserved. Most of the areas outside of the MSHCP Conservation Area that potentially support pocket mouse populations or suitable habitat tend to be already fragmented and would have poor suitability for long-term conservation.
The Incidental Take of the Los Angeles pocket mouse is difficult to quantify for the following reasons: 1) their use of burrows for diurnal resting sites; 2) finding a dead or impaired specimen is unlikely; 3) losses may be masked by seasonal or annual fluctuations in numbers; and 4) limited knowledge of its distribution within the Plan Area. However, the maximum level of Take of the Los Angeles pocket mouse could be anticipated by the loss of the number of acres of habitat that will become unsuitable for this species. As shown in Table 1, approximately 19,508 acres (37 percent) of suitable habitat is outside the MSHCP Conservation Area.
Scattered occurrence records for the Los Angeles pocket mouse exist throughout the Plan Area, with the exception of the southwest portion. While the Los Angeles pocket mouse apparently is widespread in the Plan Area, most of the records are vague regarding location. The MSHCP database includes a total of 80 records for the species, but only seven of the records are precision 1 (i.e., an "x" and "y" coordinate that allows for a relatively precise location) and five are precision 2 (one "x" or "y" coordinate or equivalent that allows a reasonably precise location). The remaining 68 records are precision codes 3 and 4 that do not allow for a precise location of the record. Most of the latter records are from the Los Angeles County and San Diego Museums of Natural History. Forty of the records were collected in the 1990's, eight in the 1980s, 27 between 1930 and 1958, and four before 1930. No records were collected in the 1960s and 1970s. Eighteen of the records, including several from the 1980s and 1990s, are mapped as residential/urban/exotic land covers, and thus are no longer extant or possibly represent mapping registration errors.
The lack of information for the Los Angeles pocket mouse may reflect several factors. Some biologists believe that this species is in serious decline within western Riverside County because it is seldom trapped and much of its suitable habitat has been lost. However, even when a population is found, densities appear to be low compared to other rodent species. Only a few individuals may be trapped in several hundred trap nights (Behrends, pers. obs.). Also, inexperienced biologists may confuse the Los Angeles pocket mouse with juveniles of the other sympatric pocket mice such as Chaetodipus fallax or C. californicus. Finally, the Los Angeles pocket mouse enters torpor (dormancy) under cold conditions and may not be trappable at all during the fall and winter months. Even during the warmer months, only a small proportion of the individuals in a population may be active on the surface at any given time.
Habitat of the Los Angeles pocket mouse has never been specifically defined, although Grinnell (1933) indicated that the subspecies "inhabits open ground of fine sandy composition" (cited in Brylski et al. 1993). This observation is supported by others who also state that the Los Angeles pocket mouse prefers fine, sandy soils and may utilize these soil types for burrowing (e.g., Jameson and Peters 1988). This subspecies may be restricted to lower elevation grassland and coastal sage scrub (Patten et al. 1992).
Vegetation associations probably are important for the Los Angeles pocket mouse and, like other heteromyid species, it probably prefers sparsely vegetated habitats. For another subspecies, the Pacific pocket mouse (P. l. pacificus), evidence indicates that mice avoid dense grass cover because of difficulty locomoting and finding seeds (M. Pavelka 1998-99; cited in Spencer and Schaefer 2000). However, soil characteristics probably also must be appropriate for a site to support the Los Angeles pocket mouse. Nonetheless, the habitat associated with the MSHCP database records for which precision codes are level 1 or 2 include non-native grassland, Riversidean sage scrub, Riversidean alluvial fan sage scrub, chaparral and redshank chaparral.
The historic range of the Los Angeles pocket mouse was estimated to be from Burbank and San Fernando in Los Angeles County east to the City of San Bernardino, San Bernardino County (the type locality) (Hall 1981). Its range extends eastward to the vicinity of the San Gorgonio Pass in Riverside County, and southeast to Hemet and Aguanga, and possibly to Oak Grove, in north-central San Diego County (Hall 1981; Patten et al. 1992).
The inland valleys from San Bernardino south to the vicinity of Temecula appear to be the remaining stronghold for this subspecies. According to the MSHCP database, captures of the Los Angeles pocket mouse in the 1990's have occurred in the Anza Valley, Cactus Valley, at several locations along the San Jacinto River between Valle Vista in the south and the San Jacinto Wildlife Area in the north, east of the current terminus of Murrieta Hot Springs Road, along Highway 79 in the Temecula-Pauba Valley area, and in Moreno Valley near March Air Reserve Base (ARB) and adjacent to Alessandro Avenue. Other known locations in the 1990s not in the database include along the southern base of Double Butte and open grassland just east of Lake Perris (Behrends, pers. obs.).
San Jacinto, Anza, Aguanga, Valle Vista, Badlands, Banning, Beaumont, Cabazon, Potrero Valley, Temecula, Vail Lake, Cactus Valley, March ARB, Moreno Valley, Reche Canyon, Hemet, Riverside East, Winchester, French Valley, Murrieta Hot Springs, Temecula Creek, San Timoteo Creek, San Jacinto River, Lake Perris State Recreation Area, and San Jacinto Wildlife Area.
Very little biological information is available specifically for the Los Angeles pocket mouse (P. l. brevinasus). Therefore, the common name used in this section where appropriate, is the little pocket mouse, which refers to the species P. longimembris.
Genetics: The Los Angeles pocket mouse (P. l. brevinasus) is one of 16 subspecies of the little pocket mouse (Williams et al. 1993). The diploid number of chromosomes for the little pocket mouse is 56. There are no published data at this time of the genetic structure and diversity of the little pocket mouse. Genetic studies of different subspecies and populations of the little pocket mouse utilizing mitochondrial DNA (mtDNA) and nuclear microsatellites techniques currently are being conducted by Dr. James Patton of UC Berkeley. While the focus of the Patton study is on the recovery of the endangered Pacific pocket mouse (P. l. pacificus), the results of this study should be very relevant and important to the MSHCP.
Diet and Foraging: Like other heteromyids (pocket mice, kangaroo rats, and kangaroo mice), little pocket mice primarily are granivores (seed eaters). However, the little pocket mouse may specialize more on grass seeds than do other pocket mice and kangaroo rat species. For example, Meserve (1976) offered a variety of seeds to Pacific pocket mice (P. l. pacificus) "cafeteria" style and found that they strongly selected the seeds of ripgut grass (Bromus [rigidus] diandrus), foxtail chess (Bromus madritensis ssp. rubens), and purple needlegrass (Nassella [Stipa] pulchra). Forbs and perennial seeds selected (at least 26-50 percent consumed) included cudweed aster (Lessingia [Corethrogyne] filaginifolia), cotton-batting plant (Gnaphalium [chilense] stramineum), and rosin-weed (Osmadenia [Calycadenia] tenella). Whether the Los Angeles pocket mouse selects seeds of these species similar to the Pacific pocket mouse is unknown. All these plant species, except perhaps rosin-weed, are common in the range of the Los Angeles pocket mouse.
Beyond specialization on seeds, little is known of the foraging behavior of the Los Angeles pocket mouse. However, Reichman and Price (1993) provide a comprehensive treatment of heteromyid foraging that probably is generalizable to the Los Angeles pocket mouse. Pocket mice possess external, fur-lined cheek pouches that promote collecting and caching of seeds either in scatter- or larderhoards, but it is not known which pattern the Los Angeles pocket mouse exhibits in the wild. However, laboratory tests by Lawhon and Hafner (1981; cited by Price and Jenkins 1986) found that little pocket mice cached seeds in larderhoards more often than two kangaroo rat species (Dipodomys merriami and D. panamintinus). Price and Jenkins (1986) suggest that larderhoarding by little pocket mice may be related to their dormancy (torpor) in the winter.
Pocket mice (Chaetodipus, Perognathus) tend to forage under shrub and tree canopies, or around rock crevices, in contrast to kangaroo rats (Dipodomys ssp.) and kangaroo mice (Microdipodops spp.) which tend to forage in more open areas (Reichman and Price 1993). Brown and Lieberman (1973) observed the little pocket mouse foraging around clumps of vegetation. Kenagy (1973) also observed that little pocket mice rarely occurred in the open and spent most of their time in or near bushes. The reliable occurrence of different species in different microhabitats is well documented, but reasons for these microhabitat preferences are not well understood (Reichman and Price 1993). Factors such as inter-specific competition, foraging economics, and predation risk probably are important factors in microhabitat selection, but the mechanisms and functions of such selection are not known.
Daily and Seasonal Activities: The daily activities of the Los Angeles pocket mouse have not been studied, but various studies of the little pocket mouse indicate that its daily activity patterns are similar to other heteromyid rodents (e.g., Kenagy 1973; O'Farrell 1974). Little pocket mice primarily are nocturnal, with an initial bout of surface activity within two to four hours after sunset and then declining activity throughout the night. In spring and summer, there may be a smaller bout of surface activity before sunrise (O'Farrell 1974).
Little pocket mice exhibit a distinct seasonal pattern in surface activity (Chew and Butterworth 1964; Kenagy 1973; O'Farrell 1974). During the colder months the little pocket mouse may enter into torpor and not engage in surface activity. For example, in a study of a rodent community in west-central Nevada, O'Farrell (1974) recorded little pocket mice on the surface beginning in April, with peak abundances in June and July. By August, surface activity was in decline and was almost absent in October. No surface activity was recorded from November to March. Likewise, Chew and Butterworth (1964) did not trap the otherwise common little pocket mouse during most of the fall and winter months in Joshua Tree in the Mojave Desert. Kenagy (1973) observed similar patterns in the Great Basin Desert, with peak surface activity occurring from May through August and little activity between October and March. Surprisingly, Kenagy recorded surface activity at surface temperatures as low as -10o Celsius. This pattern of seasonal activity is apparent with the Los Angeles pocket mouse in the MSHCP Plan Area. For example, a total of five individuals were trapped on two different grids at Lake Perris in June 1996, but no individuals were trapped on the same trap lines in October of the same year (Dudek & Associates, Inc. 1997). Kenagy (1973) observed that males emerged on the surface earlier than females after their dormant period.
Kenagy (1973) attributes the little pocket mouse's decrease in winter activity to an increase in the cost-benefit ratio of foraging. During the winter energy maintenance requirements increase while the availability of food decreases. At some point when surface conditions are very cold and food is scarce, the animal cannot meet its energy needs by foraging and thus must shut down surface activity to survive the winter. During this period of dormancy, pocket mice survive on the food they have cached to their burrows.
Reproduction: As with other heteromyids, P. longimembris are not prolific breeders. In the laboratory Hayden et al. (1966) recorded typical gestation periods of 22-23 days. Females apparently are capable of breeding in their natal season and are reproductively active by as early as 41 days of age. In the wild, little pocket mice may produce one or two litters per year with typical litter sizes of 3-4 pups. Chew and Butterworth (1964) had few observations of reproduction in a population of the little pocket mouse in Joshua Tree, but reported pregnant females, males with testicular development, and very young animals in February through April. Kenagy (1973) found that males showed testicular enlargement within several weeks of emergence following the dormant period. Females showed evidence of vaginal activity (opening, swelling, and bleeding) shortly after emergence in the spring to September or October.
Survival: There are little data on survival in the wild in the little pocket mouse. It may live up to eight years in captivity (Edmonds 1972). In the wild, Chew and Butterworth (1964) recorded about 30 percent survival from one spring to the next in a population in Joshua Tree. They attributed this relatively high survival rate to the species' entering torpor during the cold months. Over three winters, Kenagy (1973) reported survival of 82 percent, 56 percent, and 36 percent from autumn to spring. In the year of highest survival, pocket mice were active all winter and the food supply was greater than the following two winters. In the following two winters, rainfall was below normal, presumably food supplies were scarce, and individuals entered dormancy. Kenagy's data indicate that dormancy is not a strategy to maximize survival, as Chew and Butterworth appear to suggest, but rather a strategy to minimize mortality. That is, when conditions support a low cost-benefit ratio of surface activity, survival is highest. When conditions are poor and the cost-benefit ratio of surface activity increases, dormancy provides the best opportunity to survive the winter.
Dispersal: An ongoing study of movement and dispersal by the Pacific pocket mouse on the Dana Point Headlands site in southern Orange County showed an average maximum distance moved of 19.7 meters, with a range of 4.0 to 87.0 meters (Spencer and Schaefer 2000). For adults the mean maximum distance was 26.4 meters and for young-of-the-year the mean distance was 18.9 meters. However, the Dana Point site is small and may limit the distance pocket mice may move compared to larger habitat areas. There are some data from MCB Camp Pendleton suggesting that juveniles may move up to several hundred meters between habitat patches in an "unconstrained system" (Spencer and Schaefer 2000). Trapping data from Chew and Butterworth at Joshua Tree indicate that the little pocket mouse shows high site fidelity from year to year. Of 19 individuals trapped in a second spring, 16 were trapped within two trap stations (100 feet) of the previous year, and of these 16, eight were trapped one station away (50 feet) from the previous year.
Socio-Spatial Behavior: Heteromyids (pocket mice, kangaroo rats, and kangaroo mice) in general are asocial, solitary animals. Except during reproduction, they do not frequently engage in direct social encounters. Based on a trapping study in west-central Nevada, O'Farrell (1980) determined that little pocket mice home ranges overlapped during the peak breeding season of May through July, with a later peak in the second half of August. No overlap was observed when surface population numbers were low in April and September-November. In contrast to many other heteromyids, little pocket mice in this study showed more female-female range overlap than male-male overlap. O'Farrell (1980) characterizes the little pocket mouse as relatively more social than other heteromyids studied.
Crude estimates of home range size were made by Chew and Butterworth (1964) for the Joshua Tree population based on grid trapping data. They reported home range diameters of 38.7 meters to 85.4 meters, with an average of 64.3 meters. Circular home ranges based on these diameters would be 0.1 ha (0.25 acre) to 0.5 ha (1.2 acres), with an average of 0.3 ha (0.74 acre). In the Nevada desert, Maza et al. (1973) reported home ranges of females to be 0.5 ha (1.2 acres) to 3.1 ha (7.6 acres) and for males 0.3 ha (0.7 acre) to 1.9 ha (4.7 acres). Kenagy (1973) never trapped an individual little pocket mouse in more than one quadrat (each quadrat was 62.5 meters to the nearest quadrat) and he concluded that individuals moved much less than 50 meters during the night.
Population densities in the Chew and Butterworth (1964) study were 0.7 to 1.7 individuals/ha.
Community Relationships: The community ecology of heteromyid rodents, including kangaroo rats (Dipodomys spp.), pocket mice (Perognathus and Chaetodipus spp.) and kangaroo mice (Microdipodops spp.) is among the most studied aspect of this family's biology. Brown and Harney (1993) provide a comprehensive overview and attempted synthesis of this complex subject.
Arid grassland and desert environments support a surprising diversity of coexisting rodent granivores. The diversity and number of coexisting species varies depending on local conditions and the requirements of the constituent species. The Los Angeles pocket mouse in western Riverside County probably overlaps with at least four kangaroo rat species (D. agilis, D. merriami, D. stephensi and D. simulans), two other pocket mice (Chaetodipus californicus and C. fallax), and at least six native murids (Peromyscus maniculatus, P. eremicus, P. californicus, Neotoma lepida, N. fuscipes, and Reithrodontomys megalotis) that potentially compete for space and food resources. Brown and Harney (1993) conclude that "the composition of these assemblages is not random. Instead it is determined by interactions of the species with the physical environment, with other kinds of organisms, and with other rodent species." page 646. Generally, species that do coexist tend to occupy and exploit different microhabitats or niches or differ in their seasonality of resource exploitation.
Interspecific competition is an important component of the organization of heteromyid community structure. For example, competitive exclusion can result in nonrandom assemblages that partition the resources and habitats in the community. Other potential mechanisms of resource partitioning listed by Brown and Harney (1993) include habitat selection or restriction, independent adaptations, food partitioning and variable foraging efficiency, seed distribution, resource variability, predator-mediated coexistence, aggressive interference, and seasonality. It was noted above that little pocket mice tend to forage under and near shrubs and avoid open spaces that are more likely to be used by kangaroo rats (Brown and Lieberman 1973; Kenagy 1973).
Pocket mice and other heteromyid rodents also modify their environments (Brown and Harney 1993; Price and Jenkins 1986). They dig burrows, which moves the soils and provides habitat and refugia for other species, including other rodents, reptiles, amphibians, birds and invertebrates. Collection, storage and consumption of seeds by kangaroo rats, for example, has profound effects on the vegetation structure of the habitats they occupy (Price and Jenkins 1986). In addition, resource use by pocket mice and kangaroo rats substantially overlaps with that of seed-eating birds and harvester ants. However, in a literature review of effect of granivorous rodents on the plant community, Price and Jenkins (1986) cautioned against drawing broad generalizations because specific effects will be affected by competitor densities, climate and edaphic conditions, rodent densities, seed preferences, and caching behavior.
The coevolutionary results of such inter- and intraspecific community relationships and their relationship to plant communities are not understood, but it can be concluded that rodents are an important component of arid ecosystems. In addition to their direct impacts on plant communities, they are important prey for a variety of predators and their presence also affects populations of other prey such as small reptiles, lagomorphs and some birds (Brown and Harney 1993).
Physiological Ecology: The little pocket mouse has demonstrated several physiological adaptations that allow it to survive in extreme and unpredictable environments. Perhaps best known is its ability to enter torpor or hibernate for long periods during the cold winter months. This trait is thought to be a means to conserve hoarded food during their seasonal dormancy and reflects the cost-benefit ratio of foraging on the surface during the winter (Kenagy 1973). Little pocket mice enter torpor through slow-wave sleep, which may itself be a mechanism for energy conservation in many species (French 1993). The timing of torpor and dormancy appears to be at least partly endogenously controlled because little pocket mice show distinct phases of dormancy and activity under constant conditions of temperature, photoperiod and food availability in the laboratory (French 1993). Also, the disappearance of mice from the surface in the wild is asynchronous (O'Farrell 1974) and the cycle of dormancy can be changed by hormonal manipulation and not allowing animals to build up a food hoard (French 1993). Kenagy (1973) reported that little pocket mice can remain torpid for more than 72 hours at 3 percent of their normal basal metabolic rate (BMR).
Another physiological mechanism that allows little pocket mice to survive in extreme environments is a low BMR. Their BMR is 51-81 percent of that expected based on their body mass. Also, this species has been demonstrated to rest at their lower end of thermoneutrality whenever possible (French 1993).
Little pocket mice have relatively low rates of evaporative water loss compared to most mammals that is accomplished through a reduction in respiratory and cutaneous water losses (French 1993). It is not known whether little pocket mice are completely independent of exogenous water, as are at least three other heteromyids (Dipodomys merriami, Chaetodipus fallax, and C. penicillatus). Other potential mechanisms for conserving water include reduced fecal water loss and reduced lactational water loss.
Potential behavioral adaptations for maintaining water balance, energy, and thermoneutrality are remaining in day burrows during periods of climatic extremes, plugging burrow entrances to retain moisture (i.e., humidity) in the burrow (Kenagy 1973), and ingestion of herbaceous and succulents plants (possibly to support lactation). Kenagy also found that little pocket mice in the Great Basin Desert position themselves in their burrow in relation to soil temperatures that vary daily and seasonally. For example, in the early spring, little pocket mice moved from a depth of 30-40 cm where the temperatures were 12-14o Celsius to within 1 cm of the surface by midmorning, where temperatures reached 29o by midday.
Habitat Loss and Fragmentation: Urbanization, agriculture, sand and gravel mining, and flood control projects are serious threats to the Los Angeles pocket mouse. Loss of and disruptions in the continuity of drainages and alluvial fan habitats that support patchy distributions of the species probably results in isolation of local populations and preclude or limit the amount of genetic exchange between populations. Such isolation can result in genetic drift and loss of heterogeneity in the populations, leaving small local populations at high risk of extirpation. Furthermore, the loss of large areas of sandy loam habitats in occupied bottom lands may also adversely affect this subspecies (S. Montgomery 1998).
Disease: Whitaker et al. (1993) report a variety endo- and ectoparasites and associates carried by the little pocket mouse. Little pocket mice carry rickettsia, which are small, non-motile or bacterial-like organisms, including Coxiella burnetii that causes Q fever and Rickettsia rickettsii which causes Rocky Mountain spotted fever. Both are carried by tick vectors. One flagellate protozoan, Tritrichomonas muris, is carried by the little pocket mouse. One tapeworm (Cestoda), Mathevotaenia deserti, and one roundworm (Nematoda), Protospirura dipodomis, also have been reported in little pocket mice. Mites (excluding chiggers) found on little pocket mice include Androlaelaps fahrenholzi, Echinonyssus hilli, E. incomptis, E. triacanthus, E. utahensis, Eubrachylaelaps circularis, Hypoaspis leviculus, Ischyropoda armatus, I. furmani, and Sertitympanum sp. Chiggers found on little pocket mice include Dermadelema furmani, D. lynnae, D. mojavense, D. sleeperi, Euschoengastia decipiens, E. heteromyicola, E. obscura, E. stephensi, Euschoengastoides imperfectus, Eutrombicula belkini, Hexidionis deserti, H. doremi, Hyponeocula arenicola, H. fovea, H. imitator, Odontacarus linsdalei, Otorhinophila desertorum, and O. xerophila. Ticks reported from little pocket mice include Dermacentor parumapterus, Ixodes kingi, and I. sculptus. Finally, fleas reported from little pocket mice include Meringis dipodomys, M. hubbardi, M. parkeri, and Rhadinopsylla sectilis. It is not known how harmful these parasites and associates are to little pocket mice, or what level of mutulism has evolved (e.g., benefits that might occur to the host) (Whitaker et al. 1993).
One of the most unique aspects of little pocket mouse biology, and one that makes it difficult to study, is its trait of entering long periods of dormancy during the winter. Some have suggested (e.g., Chew and Butterworth 1964) that this dormancy is related to its longevity (although it was noted above that year-to-year survival was positively related to winter surface activity, mild weather conditions and high food production [Kenagy 1973]). Also, this species may not breed during poor conditions (O'Farrell 1974) and, as a result, may limit surface activity some years. These traits make this species difficult to census and monitor population trends.
The Los Angeles pocket mouse has an affinity for sandy soils characteristic of intermittent washes, but also sandy areas of aeolian (windblown) origin such as the Colton dune formation is the western portion of the Plan Area. Habitats with these microhabitat features should receive strong consideration for preservation.
Brown, J.H. and B.A. Harney. 1993. Population and community ecology of heteromyid rodents in temperate habitats. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 618-651.
Brown, J.H. and G.A. Lieberman. 1973. Resource utilization and coexistence of seed-eating desert rodents in sand dune habitats. Ecology 54:788-797.
Brylski, P., L. Barkley, B. McKernan, S.J. Montgomery, R. Minnich, and M. Price. 1993. Proceedings of the Biology and Management of Rodents in Southern California Symposium. San Bernardino County Museum, Redlands, California, June 26, 1993. Presented by the Southern California Chapter of the Wildlife Society.
Chew, R.M. and B.B. Butterworth. 1964. Ecology of rodents in Indian Cove (Mojave Desert), Joshua Tree National Monument, California. Journal of Mammalogy 45:203-225.
French, A.R. 1993. Physiological ecology of the heteromyidae: economics of energy and water utilization. In Genoways, H.H. and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10, The American Society of Mammalogists, pp. 509-538.
Davis, D.E. 1982. Calculations used in census methods. In D.E. Davis (ed.) Handbook of Census Methods for Terrestrial Vertebrates. CRC Press, Inc., Boca Raton, Fl., pp 344-369).
Dudek & Associates, Inc. 1997. Final Report: Stephens'' kangaroo rat monitoring program, Lake Perris State Recreation Area. Prepared for the California Department of Parks and Recreation, 22 pp. + Appendix.
Edmonds, V.W. 1973. Longevity of the pocket mouse. The Southwestern Naturalist 17:300-301.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Hayden, P., J.J. Gambino, and R.G. Lindberg. 1966. Laboratory breeding of the little pocket mouse, Perognathus longimembris. Journal of Mammalogy 47:412-423.
Jameson, E.W. Jr. and H.J. Peeters. 1988. California Mammals. University of California Berkeley Press. 403 pp.
Kenagy, G.J. 1973. Daily and seasonal patterns of activity and energetics in a heteromyid rodent community. Ecology 54:1201-1219.
Maza, B.G., N.R. French, and A.P. Aschwanden. 1973. Home range dynamics in a population of heteromyid rodents. Journal of Mammalogy 54:405-425.
Meserve, P.L. 1976. Food relationships of a rodent fauna in a California coastal sage scrub community. Journal of Mammalogy 57:300-319.
Montgomery, Steve. 31 Aug 1998/28 Sept. 1998, Personal communication to the U.S. Fish and Wildlife Service.
O'Farrell, M.J. 1980. Spatial relationships of a rodents in a sagebrush community. Journal of Mammalogy 61:589-605.
O'Farrell, M.J. 1974. Seasonal activity patterns of rodents in a sagebrush community. Journal of Mammalogy 55:809-823.
Patten, M.A., S. J. Myers, C. McGaugh, and J.R. Easton. ca 1992. Los Angeles pocket mouse (Perognathus longimembris brevinasus). Unpublished report by Tierra Madre Consultants, Riverside, California.
Price, M.V. and S.H. Jenkins. 1986. Rodents as seed consumers and dispersers. In Seed Dispersal, Academic Press, Australia, pp. 191-235.
Reichman, O.J. and M.V. Price. 1993. Ecological aspects of heteromyid foraging. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 539-574.
Spencer, W. and C. Schaefer. 2000. Pacific pocket mouse studies program phase I report: task 1 - translocation feasibility, task 3 - dispersal characteristics. Prepared for Foothill/Eastern Transportation Corridors Agencies and U.S. Fish and Wildlife Service.
Whitaker, J.O. Jr., W.J. Wrenn, and R.E. Lewis. 1993. Parasites. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 386-478.
Williams, D.F., H.H. Genoways, and J.K. Braun. 1993. Taxonomy. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 38-196.
mountain lion (Puma concolor)
State: None
Federal: None
The mountain lion is known from the Santa Ana Mountains, San Bernardino Mountains, San Jacinto Mountains, Santa Rosa Mountains and brushy foothills and riparian areas that may serve as habitat connections between core mountainous areas. The mountain lion also has been seen in the 1990s in "lowland" areas such as Lake Mathews-Estelle Mountain, Lake Skinner-Diamond Valley Lake, the Badlands and the San Jacinto Wildlife Area. Maintaining this species throughout the Plan Area will require conservation of specific core and linkage habitats and implementation of specific monitoring and management actions. This species requires large expanses of relatively undisturbed brushy and rocky habitats where its main prey--the mule deer--also occurs. In addition to needing large habitat blocks, a key factor for conservation of the mountain lion in the Plan Area is the provision of adequate dispersal and movement habitat, especially at potential bottleneck areas. Wildlife crossings of major roadways will need to be designed to accommodate mountain lions.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 319,843 acres (71 percent) of suitable habitat in the Plan Area. The majority of habitat conservation will occur in large blocks throughout the Plan Area, including the Santa Rosa Plateau-Santa Ana Mountains (79,850 acres), Agua Tibia Wilderness-Palomar Mountains (35,210 acres), Badlands-San Jacinto Mountains-Santa Rosa Mountains (174,670 acres), and San Bernardino Mountains (9,610 acres). Additional areas likely to be used by the mountain lion include Lake Mathews-Estelle Mountain (31,200 acres), Lake Skinner-Diamond Valley Lake (27,600 acres), and Vail Lake-Sage-Wilson Valley (61,900 acres).
Include within the MSHCP Conservation Area habitat linkages and movement corridors between large habitat blocks that allow dispersal and movement of mountain lions throughout the Plan Area and to areas outside of the Plan Area. Conserved habitat connections and corridors will include the following:
Within the MSHCP Conservation Area, maintain or improve functionality of dispersal routes. Existing undercrossings in key areas will be evaluated for their adequacy to convey mountain lions. Key crossings that will be evaluated include, but are not limited to, the following:
The conservation analysis primarily takes a landscape approach. The MSHCP database has relatively few records for the mountain lion and, while useful in characterizing the distribution of lions, has little value in characterizing key populations or the abundance of the lion in the Plan Area.
For the purpose of the conservation analysis, suitable habitat for the mountain lion includes chaparral, coastal sage scrub (Diegan coastal sage scrub and Riversidean sage scrub), desert scrub, Riversidean alluvial fan sage scrub, pinyon juniper woodland and scrub, riparian, coniferous forests, and oak woodlands and forest. However, the mountain lion primarily occurs in the following bioregions within the MSHCP Plan Area:
As shown in Table 1, within these bioregions the Plan Area supports approximately 452,000 acres of suitable habitat for the mountain lion. Approximately 320,000 acres (71 percent) of the suitable habitat in the Plan Area would be conserved in the MSHCP Conservation Area. Within theses bioregions in the MSHCP Conservation Area, approximately 254,00 acres are in Public/Quasi-Public ownership and 66,000 acres in the Criteria Area. With more than 320,00 acres of protected habitat, and an average density of about one lion/25,000 acres (see Beier 1993; Padley 1989, 1996), the Plan Area could support as many as 13 lions.
It is important to understand that the Plan Area comprises only a portion of the occupied mountain lion habitat in the Peninsular Ranges of southern California and that mountain lions are common in the Santa Ana Mountains to the southwest, San Jacinto and Santa Rosa mountains to the east and the Cleveland National Forest of the Palomar, Volcan and Laguna mountain ranges of San Diego County to the south and southeast. These mountain ranges support rugged and mostly undeveloped land and provide extensive lion habitat outside the Plan Area. Combined they comprise a large breeding population of the mountain lion in southern California. With the exception of the Santa Ana Mountains, these ranges provide continuous habitat for the species. Therefore, the viability of the mountain lion in the Plan Area should be viewed in the context of the Peninsular Range population.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
MOUNTAIN LION
| Vegetation Type | MSHCP Plan Area1 (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area2 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 333,517 | 40,064 | 198,533 | 238,597 | 38,324 | 56,596 | 94,920 |
| Coastal Sage Scrub | 45,784 | 18,841 | 12,309 | 31,150 | 8,901 | 5,733 | 14,634 |
| Desert Scrub | 9,376 | 3,675 | 1,313 | 4,988 | 44 | 4,344 | 4,388 |
| Juniper Woodland and Scrub | 156 | 2 | 110 | 112 | 0 | 44 | 44 |
| Riversidean Alluvial Fan Sage Scrub | 3,014 | 1,541 | 884 | 2,425 | 86 | 503 | 589 |
| Montane Coniferous Forest | 29,898 | 17 | 20,483 | 20,500 | 43 | 9,355 | 9,398 |
| Woodland and Forest | 30,031 | 1,806 | 20,265 | 22,071 | 4,620 | 3,340 | 7,960 |
| TOTAL | 451,777 | 65,946 (15%) | 253,897 (56%) | 319,843 (71%) | 52,018 (11%) | 79,915 (18%) | 131,933 (29%) |
| 1 Plan Area for the mountain lion is defined as the following bioregions: Agua Tibia Mountains, Desert Transition, San Bernardino Mountains, San Jacinto Foothills, San Jacinto Mountains and Santa Ana Mountains. 2 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. |
|||||||
Based on typical dispersal distances by juvenile males in New Mexico of 63 miles (Sweanor et al. 1996b), juveniles should be capable of dispersing throughout any part of this range. Objectives have been incorporated into the conservation strategy for this species to minimize risk to dispersing mountain lions.
As described below under Data Characterization, the few point localities in the MSHCP database are not very helpful for characterizing key populations. Also, it is obvious that the foothills and mountains of the Peninsular Ranges are the key areas for lions. Therefore, an analysis of the data points inside and outside the MSHCP Conservation Area has not been done.
As described above, the MSHCP Conservation Area includes approximately 320,000 acres of suitable habitat for the mountain lion. The total area available to mountain lions in the Peninsular Ranges, however, is much larger and generally contiguous with the Plan Area, and includes the San Jacinto Mountains east of the Plan Area, the Santa Rosa Mountains, and the Palomar, Volcan and Laguna ranges in east San Diego County. These areas are contiguous and provide relatively unobstructed habitat for mountain lions to hunt and disperse.
Perhaps more important than the amount of conserved habitat in the Plan Area is the configuration of the reserve system to accommodate movement and dispersal of mountain lions to areas such as the Santa Ana Mountains, Lake Mathews-Estelle Mountain, Lake Skinner-Diamond Valley Lake, the Badlands, and the San Bernardino Mountains. Habitat linkages between these Core Areas will be important for accommodating movement and dispersal. Mountain lions may make daily movements of approximately 10 to 12 miles per day (Laundré et al. 1996), but most of these movements will be within the Core Areas related to hunting. The critical reserve configuration issue is habitat linkages that will allow successful dispersal between Core Areas by juveniles. While juveniles are capable of dispersing long distances (Sweanor et al. [1996b] determined an average dispersal of 7.7 miles for females and 62.8 miles for males), they require sufficient cover to move safely (see Beier 1996). Dispersal connections through marginal habitat should be as short as possible. Movements that could be made within one night could occur across marginal habitats, but longer movements will require refugia for resting, such as rockpiles, brushpiles, windfalls, hollow snags, and hollow trees. Riparian habitat and dense and rocky chaparral or coastal sage scrub along longer movement corridors (e.g., longer than 10 miles) would be ideal. In addition, movement across freeways and major roads will require adequate overpasses or underpasses to reduce the chance of mortality from vehicle collisions. Open bridges are the preferred undercrossing. Culverts should be at least 10-20 feet wide to accommodate movement, with fencing and vegetative cover to funnel lions into the wildlife crossing.
As described in detail by Beier (1993), the Santa Ana Mountains population is at high risk of extirpation because the population of 20 animals at the time of the study was determined to be "demographically unstable" without a movement connection between the Santa Ana Mountains and the Palomar Mountains. These two ranges currently are separated by Interstate 15, with the only relatively unobstructed corridor along Pechanga Creek, which runs through a highly urbanized area. It has been suggested that a wildlife overpass of Interstate 15 would provide a more effective connection between the two mountain ranges. The most logical location for the overpass is at some location between the INS checkpoint near Rainbow and Temecula, but a specific location and design has not been proposed.
The only potential large mammal connections between Lake Mathews-Estelle Mountain and the Santa Ana Mountains are along Indian Canyon and possibly Horsethief Canyon. The Gavilan Hills and Plateau area is becoming increasingly populated and mountain lions using this area may be at greater risk of vehicle collisions and direct conflicts with humans. For the purpose of this conservation analysis, the Riverside Lowlands bioregion was not included because of the long-term risk to lions in this area.
The Badlands provide a northwest-southeast movement corridor connected to the San Jacinto Wildlife Area-Lake Perris to the south, the San Jacinto Mountains to the southeast and the San Bernardino Mountains to the north. The Badlands would be comprised of Criteria Area, Public/ Quasi-Public lands and rural mountainous designation areas (see discussion below). Significant obstacles to large mammal movement along the Badlands are Highway 60 and Lamb Canyon (Highway 79). The connection between the Badlands and the San Bernardino Mountains is a constrained linkage through residential and agricultural development in Cherry Valley. This linkage may not be viable for mountain lions because of the risk of vehicle collisions and interactions with humans. A more logical movement linkage lies to the east of the Plan Area near Cabazon along San Gorgonio Wash, Hathaway Creek and Banning Canyon.
In summary, conservation for the mountain lion will be achieved by inclusion of at least 320,000 acres (71 percent) of the suitable Conserved Habitat and conservation of linkages between large habitat areas. Implementation of the MSHCP would provide large habitat blocks and ensure that movement areas are adequate to support the life history needs of the mountain lion, including foraging, reproduction, and dispersal activities. The main habitat areas for mountain lions in the MSHCP Conservation Area include the Santa Rosa Plateau-Santa Ana Mountains, Agua Tibia Wilderness-Palomar Mountains, Badlands-San Jacinto Mountains-Santa Rosa Mountains, and San Bernardino Mountains. Additional MSHCP Conservation Areas likely to be used by the mountain lion include Lake Mathews-Estelle Mountain, Lake Skinner-Diamond Valley Lake, and Vail Lake-Sage-Wilson Valley.
About 132,000 acres (29 percent) of suitable habitat would be outside the MSHCP Conservation Area and individuals within these areas will be subject to Incidental Take consistent with the Plan. Of this, approximately 52,000 acres (11 percent) are in Rural/Mountainous designation areas. The habitat outside of the MSHCP Conservation Area tends to be in areas that currently are more fragmented by urban and agricultural development, and thus, less suitable for conservation of the mountain lion.
There are 25 data locations for the mountain lion in the MSHCP database. Of these 25 locations, four have a precision code of 1 (i.e., an "x" and "y" coordinate), six have a code of 2 (one "x" or "y" coordinate or equivalent), and 15 have a code of 3 (generalized location), or 4 (an ambiguous location). Dates of the locations range from 1981 to 1999. Nineteen of the 25 records are since 1990. Mountain lion records are scattered throughout the Plan Area. The only area lacking records is the northwest part of the Plan Area north of the Riverside Freeway (State Highway 91). The MSHCP database provides useful distributional data, but the relatively few locations do not accurately represent the abundance of the mountain lion in the Plan Area. The conservation analysis thus primarily will be based on habitat and landscape characteristics of the reserve rather than rely on specific geographic occurrences.
Mountain lions use rocky areas, cliffs, and ledges that provide cover within open woodlands and chaparral, as well as riparian areas that provide protective habitat connections for movement between fragmented core habitat. A study of diurnal bedding habitat in northeast Oregon suggests that lions also need both vertical and horizontal cover components, such as rocks and downed logs, to feel secure enough to bed (Akenson et al. 1996).
Of the 25 records in the MSHCP database, five are in chaparral, five in grassland, three in Riversidean sage scrub, one in coniferous forest, one in oak woodland, one in alkali playa, and three in agriculture. Five records are in residential/urban/exotic and one is in open water/reservoir. Based on the known habitat associations of the mountain lion, many of the vegetation community/land use characterizations in the database appear to be biased to areas where mountain lions would be observable rather than indicative of their typical habitat.
Mountain lions occupy a latitudinal range of 110 degrees in North and South America and occupy a broad variety of habitats from the northern limit of the Canadian forests to Patagonia in South America. Within western Riverside County, mountain lions are found intermittently throughout the mountainous and foothill regions.
Mountain lions occur in the Santa Ana Mountains, San Bernardino Mountains, San Jacinto Mountains, Santa Rosa Mountains and adjacent brushy foothills and riparian areas that may serve as habitat connections for movement between core mountainous areas.
Same as listed above.
Genetics: Thirty subspecies of mountain lions have been described. Preliminary genetic studies using both mitochondrial DNA and nuclear microsatellites as molecular markers, however, have determined that North American populations of mountain lions have relatively low genetic variation (Culver et al. 1996). This finding is significant for conservation planning because reintroduction programs have to be less concerned about introducing genetically distinct individuals.
Diet and Foraging: The diet of mountain lions includes mule deer as their principal prey, but also other ungulates, rabbits and larger rodents (Ackerman et al. 1984; Cunningham 1996; Leopold 1986; Peirce and Cashman 1996; Spalding and Lesowski 1971). In the Ackerman et al. (1984) study in southern Utah, deer more than seven years old were disproportionately taken by lions and cattle made up less than 1 percent of their diet. However, Cunningham (1996) and Peirce and Cashman (1996) found that cattle are a more substantial component of the mountain lion's diet in Arizona. In southern California, Arizona, and New Mexico mountain lions also are known to prey on desert bighorn sheep (Ovis canadensis) (Krausman et al. 1989; Logan et al. 1996a; Peirce and Cashman 1996; Rubin et al. 1996). Hemker et al. (1984) suggest that the density of resident mountain lions in southern Utah is limited by the abundance of mule deer. Leopold et al. (1986) and Peirce and Cashman (1996) suggest that mountain lions change diets to smaller prey when ungulate populations (deer, desert bighorn, collared peccary [Tayassu tajacu]) decline.
Daily Activity: Studies of general activity patterns of lions suggest that lions have peaks of activity around sunset and sunrise (Laundré et al. 1996; Van Dyke et al. 1986). Laundré et al. (1996) found that lions in south-cental Idaho and northwestern Utah moved approximately 10 miles (males) to 12 miles (females) per day and that most of the day was spent in low level activities of walking and feeding.
Reproduction: Sweanor et al. (1996a) studied the reproductive biology of mountains lions in the San Andres Mountains of southern New Mexico from 1986 to 1994. Thirty-nine females produced 79 litters, with an average size of 3.02 cubs (range 2-4) in 53 litters observed in the first 9-49 days. Twenty-one litters observed from 52-427 days had a mean litter size of 2.19 cubs. Sex ratios were virtually equal in the litters observed in the first 9-49 days, but females outnumbered males in the litters observed from 52-427 days, indicating sex-related mortality in litters. Average gestation period was 91.5 days and litters were born every month except February, with peaks in August and September. Females appear to begin consorting with males at about age 21 months and first litters are produced at ages 22-40 months. There was substantial variation in female reproductive success in this population. While 39 of 53 (73 percent) females reproduced, 50 percent of the cubs were produced by only 26 percent of the females. Interbirth intervals for litters in which at least one cub survived to independence or 12 months of age averaged 17.4 months. After the loss of a litter, it took females an average of 100 days to successfully rebreed.
Survival: A study of lion cub survival rates indicates that annual survival rates of unhunted lions in southern New Mexico is about 70-72 percent, depending on the method for calculating survival (Logan et al. 1996b). Natural causes of mortality, in order of frequency, include cannibalism, starvation, disease, accidental fall and coyote predation (Logan et al. 1996b). Mean annual subadult survival was 87 percent for females and 60 percent for males, and all deaths were from intraspecific killing. Mean annual adult female survival was 81 percent and male survival was 90 percent.
Dispersal: A study of dispersal by juvenile mountain lions in the Santa Ana Mountain Range showed that dispersal is initiated by the mother abandoning her cub of about 18 months at the edge of her range (Beier 1996). The cub disperses to the part of urban-wildlife interface farthest from its natal range and uses temporary home ranges near this interface. Beier (1996) also observed dispersing individuals using corridors along well covered travel routes, an underpass, areas lacking artificial lighting, and areas with low residential densities (<1 dwelling unit/16 hectares). A dispersal study by Sweanor et al. (1996b) of a population in the San Andres Mountains of southern New Mexico showed dispersal at an average of 13.5 months for females and 15.7 months for males. Sixty percent of the females did not disperse from their natal range, whereas all males did. Females dispersed on average 7.7 miles and males dispersed on average 62.8 miles. Over the five-year study period, 21 progeny and 22 immigrants were recruited into the San Andres Mountains, and 47 progeny successfully dispersed outside of the mountain range.
Socio-Spatial Behavior: Socio-spatial information (home range, spatial overlap, population densities) for mountain lions is quite variable. Padley (1989, 1996) monitored female home ranges in the Santa Ana Mountains. He found that annual home ranges varied from 32 to 87 sq. miles, with a mean range of 43 sq. miles, and that home ranges of females with kittens were smaller. Padley also found that home ranges were stable from year to year and suggested that this stability may be related to the abundance of mule deer populations. Loft (1996) reported average male home ranges of 139 sq. miles in the winter and 176 sq. miles in the summer in the Sierra Nevadas. Average female home ranges were 63 and 117 sq. miles in the winter and summer, respectively. Mean spatial overlap of ranges in this study was 32 percent between females, 23 percent between males, and 31 percent between sexes. Lion densities were 1.2 to 2.0 lions per 100 sq. miles in the summer and 1.4 to 3.0 in the winter. Peirce and Cashman (1996) recorded home ranges of 93, 159, and 304 sq. miles in southwestern Arizona. Pittman et al. (1996) recorded male home ranges of 122 to 350 sq. miles and female home ranges of 78 to 150 sq. miles in the Trans-Pecos region of Texas. Based on a study of mountain lion feeding habits in the eastern Sierra Nevada, Pierce et al. (1996) suggest that prey density may be the most important factor regulating mountain lion populations.
Community Relationships: Mountain lions can be expected to compete with other carnivores such as bears, bobcats, and coyotes for prey. A study of the ecological relationship between black bears (Ursus americanus), grizzly bears (Ursus arctos) and mountain lions in Glacier National Park in Montana and Yellowstone National Park in Wyoming found that bears displace lions from kills and that displaced lions lost an average of 1.1 kg/day of ungulate biomass, or 25-40 percent of their daily food requirements (Murphy et al. 1996). In addition, lions killed a higher number of ungulates when they were displaced by bears. Ruth and Hornocker (1996) documented grizzly bears tracking, treeing and killing mountain lions in Montana. Direct competition with bears may not be a problem at present in western Riverside County, but, because the black bear population in the San Jacinto Mountains may increase in the future, such competitive relationships may become increasingly important. A study of seasonal resource use by mountain lions, bobcats and coyotes in central Idaho found that when resource use among these species overlapped in the winter, lions killed both bobcats and coyotes when defending or taking over a kill (Koehler and Hornocker 1991). Mountain lions in western Riverside County may compete with coyotes and bobcats for food resources when their preferred prey, mule deer, is scarce.
The primary threats to the mountain lion are habitat fragmentation, loss of large areas of undeveloped land, road kills, indiscriminate shootings, animal control measures, and loss of natural prey base. Using a simulation model, Beier (1993) estimated that lions were at a low extinction risk in areas at least 2,200 sq. km. in size (about 544,000 acres). The risk of extinction increases in smaller areas in the absence of immigration. For example, Beier (1993) estimated that the mountain lion population of about 20 adults in the Santa Ana Mountains in an area of 2,070 sq. km. was demographically unstable and that a movement corridor connection to the Palomar Mountain Range to the east will be important for sustaining this population.
Human presence also may have adverse effects on mountain lion behavior, and in particular range use and foraging activities. For example, Van Dyke et al. (1986) studied the reactions of mountain lions to logging and human activity and found that near human presence, lion activity peaks shifted to periods after sunset compared to areas with no human activity where activity peaks occurred within two hours of sunset and sunrise. In addition, juvenile lions encountered humans more frequently than adult lions, suggesting that dispersing juveniles are at relatively high risk of encounters with humans. Selected home ranges of both adults and juveniles were in areas with lower road densities, no recent timber sales, and few or no human residences. On the other hand, Jalkotzy and Ross (1996) found that mountain lions were relatively unaffected by summertime human activity (vehicular traffic and camping, equestrian and hiking activities) at Sheep River, Alberta, Canada, although they did suggest that lions may be more sensitive at kill sites than along travel routes.
Mountain lions are at risk to a variety of diseases, including feline immunodeficiency virus, feline leukemia virus, feline infectious peritonitis, canine distemper, panleukopenia, and rabies (Foley 1996). Mortality from diseases is a potential catastrophe for small, isolated mountain populations.
Mountain lions require large areas for hunting their preferred prey (mule deer) and Beier (1993) has shown through modeling that lion populations require at least 850 sq. miles to remain stable. Human developments have intruded upon, greatly reduced and fragmented this required habitat, thus resulting in apparent increased interactions between humans and mountain lions (e.g., Torres et al. 1996). This interaction has resulted in adverse impacts on mountain lions in addition to habitat loss and fragmentation: increased mortality of lions from vehicular collisions; and apparent loss of fear of humans by lions and consequently more frequent aggressive behavior toward humans (especially by juvenile lions). Sustaining mountain lion populations in the Transverse and Peninsular mountain ranges (the San Bernardino, San Jacinto, Santa Rosa, Palomar, Laguna, and Santa Ana ranges) will require substantial habitat linkages between ranges. The connection between the Santa Ana and Palomar ranges already is extremely constrained by Interstate 15 and the Santa Ana population is at serious risk of extirpation. A wildlife overpass is under consideration for Interstate 15 (Robert Fisher, pers. comm.).
The work of Sweanor et al. (1996a) indicates that females exhibit substantial variation in reproductive success; 50 percent of the offspring were produced by 26 percent of the females. It is likely that male productivity is even more variable. With such variability in production, small, isolated populations are at relatively greater risk of losing highly productive individuals and more prone to breeding depression and local extinction.
The relatively low genetic variation found by Culver et al. (1996) is significant for conservation planning because reintroduction programs have to be less concerned about introducing genetically distinct individuals. Finally, maintaining an adequate prey base of mule deer in the region will be crucial for sustaining the mountain lion.
Ackerman, B.B., F.G. Lindzey, and T.P. Hemker. 1984. Cougar food habitats in southern Utah. Journal of Wildlife Management 48:147-155.
Akenson, J. , M. Henjum, and T. Craddock. 1996. Diurnal bedding habitat of mountain lions in northeast Oregon. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Beier, P. 1996. Dispersal of juvenile cougars in fragmented habitat. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Beier, P. 1993. Determining minimum habitat areas and habitat corridors for cougars. Conservation Biology 7:94-108.
Beier, P. 1995. Dispersal of juvenile cougars in fragmented habitat. Journal of Wildlife Management 59:228-237.
Culver, M., M. Raymond, W. Johnson, M. Roelke, and S. O'Brien. 1996. Characterization of genetic variation in the puma (Puma concolor). [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Cunningham, S.C. 1996. Prey availability and selection by mountain lions in the Aravaipa-Klondyke area of Arizona. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Fisher, Robert. 9 June 1999. Personal communication regarding wildlife distribution and planning issues.
Foley, J. 1996. The role of infectious disease in population control and regulation of western mountain lions. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Hemker, T.P., F.G. Lindzey, and B.B. Ackerman. 1984. Population characteristics and movement patterns of cougars in southern Utah. Journal of Wildlife Management 48:1275-1284.
Jalkotzy, M.G. and Ross, I.P. 1996. Cougar responses to human activity at Sheep River, Alberta. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Koehler, G.M. and M.G. Hornocker. 1991. Seasonal resource use among mountain lions, bobcats, and coyotes. Journal of Mammalogy 72:391-396.
Krausman, P.R., B.D. Leopold, R.F. Seegmiller, and S.G. Torres. 1989. Relationships between desert bighorn sheep and habitat in western Arizona. Wildlife Monographs 102:1-66.
Laundré, J.W., C.A. López-González, and K.B. Altendorf. 1996. Daily and hourly summer activity levels of free roaming mountain lions. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Loft, E.R. 1996. Spatial-temporal analyses of mountain lions in the Sierra Nevada: looking for pattens and "bulls-eyes" amid the mess. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Leopold, B.D. and Krausman, P.R. 1986. Diets of 3 predators in Big Bend National Park, Texas, Journal of Wildlife Management 50:290-295.
Logan, K.A. , L.L. Sweanor, and M.G. Hornocker. 1996a. Effects of cougar (Felis concolor) predation on desert bighorn sheep (Ovis canadensis mexicana) in the San Andres Mountains, New Mexico. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Logan, K.A. , L.L. Sweanor, and M.G. Hornocker. 1996b. Survival and mortality of cougars (Felis concolor) in the San Andres Mountains, New Mexico. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Murphy, K.M., G.S. Felzien, M.G. Hornocker, and T.K. Ruth. 1996. Ecological relationships between bears and predation by cougars on ungulates. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Padley, W.D. 1996. Female mountain lion (Felis concolor) home ranges in the southern Santa Ana Mountains, California. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Padley, W.D. 1989. Mountain lion ecology in the southern Santa Ana Mountains, California. Prepared for the California Department of Fish and Game, Final Report Contract No. 87-M-6250, 27 pages.
Peirce, M.F. and J.L. Cashman. 1996. Movements and diets of mountain lions in southwestern Arizona. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Pierce, B. 1996. Implications of mountain lion movements for population regulation and conservation. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Pittman, M.T., B.P. McKinney, and G. Guzman. 1996. Ecology of the mountain lion on Big Bend Ranch State Park in Trans-Pecos Texas. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Rubin, E., W. Boyce, C. Hayes, S. Torres, and M. Jorgensen. 1996. Mountain lion predation on bighorn sheep in the peninsular ranges of California. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Ruth, T.K. and M.G. Hornocker. 1996. Interactions between cougars and wolves (and a bear or two) in the north fork of the Flathead River, Montana. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Spalding, D.J. and J. Lesowski. Winter food of the cougar in south-central British Columbia. Journal of Wildlife Management 35:378-381.
Sweanor, L.L., K.A. Logan, and M.G. Hornocker. 1996a. Reproductive biology of female cougars (Felis concolor) in the San Andres Mountains, New Mexico. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Sweanor, L.L., K.A. Logan, and M.G. Hornocker. 1996b. Dispersal of cougars (Felis concolor) in metapopulation dynamics. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Torres, S.G., T.M. Mansfield, and J. Foley. 1996. Mountain lion depredation and human activity in California: testing speculations. [Abstract]. Fifth Mountain Lion Workshop. Organized by the California Department of Fish and Game and the Southern California Chapter of the Wildlife Society, San Diego, California, February 27 - March 1, 1996.
Van Dyke, F.G., Brocke R.H, H.G. Shaw, B.B. Ackerman, T.P. Hemker, and F.G. Lindzey. 1986. Reactions of mountain lions to logging and human activity. Journal of Wildlife Management 50:95-102.
northwestern San Diego pocket mouse (Chaetodipus fallax fallax)
State: Species of Special Concern
Federal: None
The northwestern San Diego pocket mouse occurs throughout the Plan Area in coastal sage scrub (including Diegan and Riversidean upland sage scrubs and alluvial fan sage scrub), sage scrub/grassland ecotones, chaparral, and desert scrubs at all elevations up to 6,000 feet. This species is considered to be fairly common in suitable habitat. No specific management regimes are needed to maintain an adequate amount of habitat for this species, although management of habitat for species such as the Stephens' kangaroo rat, San Bernardino kangaroo rat, Los Angeles pocket mouse and California gnatcatcher may benefit the northwestern San Diego pocket mouse.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 407,645 acres (56 percent) of suitable habitat in the Plan Area. Conservation in the primary core habitat areas includes Existing Core C (15,610 acres), Existing Core G (4,490 acres), Existing Core H (17,470 acres), Existing Core F (8,360 acres), Existing Core I (9,610 acres), Existing Core J (24,370 acres), Existing Core M (10,460 acres), Proposed Extended Existing Core 2 (8,100 acres), Proposed Extension of Existing Core 6 (1,180 acres), Proposed Extension of Existing Core 7 (3,220 acres), Proposed Core 1 (7,470 acres), Proposed Core 2 (5,050 acres), Proposed Core 3 (24,920 acres), Proposed Core 4 (11,890 acres), Proposed Core 5 (3,220 acres), and Proposed Core 7 (50,000 acres).
Include within the MSHCP Conservation Area approximately 18,000 acres of suitable dispersal and/or movement linkages between habitat blocks, including contiguous uplands from Estelle Mountain to Wildomar, Gavilan Hills, San Jacinto River, Kolb Creek/Arroyo Seco, Temecula Creek, Tucalota Creek, Wilson Creek, Tule Creek, and San Gorgonio Wash.
For the purpose of the conservation analysis, suitable habitat for the San Diego pocket mouse includes chaparral, coastal sage scrub (including Riversidean and Diegan coastal sage scrub), desert scrub, grassland, juniper woodland and scrub, and Riversidean alluvial fan sage scrub. Based on these assumptions about habitat, the Plan Area supports approximately 730,652 acres of suitable habitat for the northwestern San Diego pocket mouse. Table 1 shows the conservation of suitable habitat for the San Diego pocket mouse. Overall, approximately 407,645 acres (56 percent) of suitable habitat in the Plan Area would be in the MSHCP Conservation Area.
As described below in the Species Account under Data Characterization, 62 of the 218 point localities have a precision of "1" or "2." Of these 62 point localities, 26 (42 percent) would be in the MSHCP Conservation Area. The occurrence data, however, probably do not accurately reflect the conservation of the northwestern San Diego pocket mouse that would occur under the MSHCP. Many of the data points were collected during trapping programs associated with various proposed development projects. Thus the data probably are biased to areas that were proposed for some type of project and, consequently, probably less suitable for long-term conservation.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
NORTHWESTERN SAN DIEGO POCKET MOUSE
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 413,488 | 64,899 | 207,381 | 272,280 | 59,582 | 81,626 | 141,208 |
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,970 |
| Desert Scrub | 9,378 | 3,675 | 1,314 | 4,989 | 44 | 4,345 | 4,389 |
| Juniper Woodland and Scrub | 1,082 | 336 | 274 | 609 | 23 | 450 | 473 |
| Riversidean Alluvial Fan Sage Scrub | 7,149 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,915 |
| Grassland | 146,869 | 20,011 | 22,806 | 42,817 | 12,223 | 91,829 | 104,502 |
| TOTAL | 730,652 | 139,253 19% |
268,393 37% |
407,645 56% |
98,330 13% |
224,676 31% |
323,457 44% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Very little is known about the relationship between populations of northwestern San Diego pocket mice in the different parts of the Plan Area. For example, no studies have been performed to determine whether there are genetic differences in geographically distinct populations that would be important for reserve configuration, and thus whether genetic exchange between reserve areas would be important for sustaining viable populations. For this analysis, it is assumed that populations of San Diego pocket mice are confined to areas within relatively contiguous habitat and unlikely to disperse between distant isolated habitat areas through unsuitable habitat. Given the existing distribution of suitable habitat and the proposed reserve design, the Plan Area contains four main habitat complexes for the San Diego pocket mouse:
Smaller habitat areas assumed to be isolated from the larger habitat complexes are the Jurupa Mountains, Box Springs Mountain, Lakeview Mountains, Sycamore Canyon Regional Park, Norco Hills, Double Butte, Motte-Rimrock Reserve, and Warm Springs Creek. Although these areas meet the minimum area of 60 acres suggested by Bolger et al. (1997) to sustain native rodent populations, northwestern San Diego pocket mice in these areas may still be at relatively high risk of extirpation because a single catastrophic event such as a wildfire or even extreme predation pressure could devastate a local population to a level beyond recovery.
The Santa Ana Mountain foothills form a large, contiguous habitat area connected by Public/Quasi-Public lands, reserve and rural mountainous areas. This habitat complex also includes extensive contiguous habitat in north San Diego County. Much of this area is chaparral and mesic coastal sage scrub. The only significant potential barrier in this area is State Highway 74 (Ortega Highway) between Lake Elsinore and Orange County. Two other roads may be potential barriers (Clinton Keith Road/Tenaja Road and De Luz Road), but these roads are very rural with relatively low traffic levels.
Lake Mathews-Estelle Mountain is generally contiguous with the Steele Peak reserve area. State Highway 74 is a potential barrier to movement to the Kabian Park area and Railroad Canyon Road is a potential barrier to movement between Kabian and the Sedco Hills. Culverts under these roads would allow for movement of northwestern San Diego pocket mice between these areas. There is some potential for northwestern San Diego pocket mice to move between this habitat complex and the Santa Ana Mountains foothills along Indian Canyon or Horsethief Canyon, but the crossings under Interstate 15 may be too long for the northwestern San Diego pocket mouse.
By far the largest intact habitat complex for the northwestern San Diego pocket mouse is the Badlands-San Jacinto Mountain foothills-Agua Tibia Wilderness complex. This area comprises approximately the eastern one-third of the Plan Area. With the exception of several major highways, continuous habitat for the northwestern San Diego pocket mouse runs from the northwest extent of the Badlands north of Moreno Valley south to the foothills of the San Jacinto Mountains in the area of Sage and farther south to the Agua Tibia Wilderness and the Cahuilla and Anza valleys. The southern part of this habitat complex also is contiguous with habitat in San Diego County. This complex also includes the San Jacinto Wildlife Area-Lake Perris and Lake Skinner-Domenigoni core reserves.
Major roads that interrupt this large habitat area include the following:
It should be noted that a substantial amount of the Badlands habitat is designated rural mountainous, which will provide some habitat for the pocket mouse, but which will not be managed as habitat. Given the steep topography in the Badlands, it is highly likely that the majority of the area will remain undeveloped and remain suitable for the San Diego pocket mouse. A large portion of suitable habitat in the Sage area also will be designated rural mountainous, but adequate reserve in the Criteria Area will be assembled in this area to maintain habitat connections.
The Banning Bench complex includes continuous habitat along the foothills of the San Bernardino Mountains, with most of the suitable habitat for the San Diego pocket mouse in San Bernardino County.
In summary, the MSHCP Conservation Area will include at least 407,645 acres (56 percent) of suitable habitat. Much of this habitat will be in large Core Areas and habitat linkages that are suitable for occupation by the San Diego pocket mouse in four major habitat complexes: the Santa Ana Mountain Foothills - Santa Rosa Plateau complex, the Lake Mathews/Estelle Mountain - Steele Peak - Kabian Park-Sedco Hills complex, the Badlands-San Jacinto Mountain Foothills-Agua Tibia Wilderness complex, and the Banning Bench complex. Populations of the pocket mouse should remain viable in these four areas.
Approximately 323,457 acres (44 percent) of suitable habitat for the northwestern San Diego pocket mouse would be outside the MSHCP Conservation Area.
The MSHCP database includes 218 records for the northwestern San Diego pocket mouse. Of the 218 records, 45 (21 percent) are precision code ‟1" (an ‟x" and ‟y" coordinate that allows for good precision in the location), 17 (8 percent) are precision code ‟2" (one ‟x" or ‟y" coordinate or equivalent), and the remaining 156 (71 percent) are precision codes ‟3" or ‟4" (relatively imprecise locations from general areas). Most of the records are relatively recent, with 149 (68 percent) since 1990. Records prior to 1970 comprise 23 percent of the data (50 records) and records from 1970 to 1990 comprise 9 percent of the data (19 records). The preponderance of data from the 1990s probably is due to the relatively intensive trapping effort in western Riverside County for the federally-listed endangered and state-listed threatened Stephens' kangaroo rat (Dipodomys stephensi) since its federal listing in 1988. The records are scattered throughout the Plan Area, with clusters from Sycamore Canyon, Santa Rosa Plateau, Lake Skinner-Diamond Valley Lake area, the Badlands, Lake Perris-San Jacinto Wildlife Area, Lake Mathews-Estelle Mountain, Vail Lake, Sage, Aguanga and Anza Valley. There are San Diego pocket mouse records for virtually all areas with suitable habitat in the Plan Area, indicating that this species is still relatively common in suitable habitat (Behrends, pers. obs.; also see Chase et al. 2000). This species is trapped in almost all trapping programs in grassland, coastal sage scrub, and chaparral habitats. The database appears to provide a fairly good representation of the population distribution of this species in the Plan Area.
The northwestern San Diego pocket mouse inhabits coastal sage scrub, sage scrub/grassland ecotones, and chaparral communities. It inhabits open, sandy areas of both the Upper and Lower Sonoran life-zones of southwestern California and northern Baja California (in McClenaghan 1983). Bleich (1973) recorded the highest populations of the San Diego pocket mouse in coastal sage scrub supporting a mixture of coastal sagebrush (Artemisia californica) and California buckwheat (Eriogonum fasciculatum) on the Naval Weapons Station, Fallbrook Annex in northwestern San Diego County, but it was also relatively abundant in chaparral. The San Diego pocket mouse generally exhibits a strong microhabitat affinity for moderately gravelly and rocky substrates (Bleich 1973; Price and Waser 1984), and, to a lesser extent, shrubby areas (MWD and RCHCA 1995). In western Riverside County, the San Diego pocket mouse also commonly is found in disturbed grassland and open sage scrub vegetation with sandy-loam to loam soils (S. Montgomery 1998).
In the MSHCP database, 84 of 218 records (38 percent) of the San Diego pocket mouse occur in sage scrub (coastal sage scrub, Riversidean sage scrub, Riversidean alluvial fan sage scrub) and chaparral (including red shank chaparral). An additional 47 records (21 percednt) are in grassland. Other natural habitats with records include alkali playa (1 record), coast live oak woodland (1 record), riparian (2 records), and coniferous forest (2 records). A number of records are in croplands (25 records), grove/orchard (2 records), and residential/urban/exotic (42 records), but it is assumed that these populations are either no longer extant or that the mapping represents registration errors. For example, the records may be from natural habitats adjacent to agricultural and urban development. Nonetheless, the database indicates that sage scrub, chaparral, and grassland are the primary habitats for this species in the Plan Area.
Marginal records for the northwestern San Diego pocket mouse include Claremont; San Bernardino; Banning; and Jacumba (Hall 1981), and San Jacinto Lake, Riverside County (Mearns 1901). The northwestern San Diego pocket mouse occurs throughout western Riverside County and has been collected at elevations from 138 meters (452 ft) at Palm Springs, Riverside County, to 1,835 meters (6,018 ft) on the northern slopes of the San Bernardino Mountains in San Bernardino County (Lackey 1996). It is uncertain where the boundary between the northwestern San Diego pocket mouse and the pallid San Diego pocket mouse (C. f. pallidus) lies. The pallid San Diego pocket mouse occurs on the eastern slopes of the Peninsular Ranges in eastern Riverside County, but occurs in the transitional Cabazon area of Riverside County and the San Felipe Valley in San Diego County (Hall 1981). A transition zone between the two subspecies may occur in the eastern portion of the Anza or Terwilliger valleys or more to the east in the Santa Rosa Mountains. For the purpose of this analysis, it is assumed that the San Diego pocket mouse in the Plan Area is the northwestern subspecies C. f. fallax.
The San Diego pocket mouse is widely distributed throughout the Plan Area in areas of sage scrub, chaparral and non-native grassland (Behrends, pers. obs.; Montgomery 1998). The MSHCP database records encompass more than 50 general locations in the Plan Area ranging from Pedley in the west, Reche Canyon in the north, Temecula in the south, and Anza in the east. Additional main localities for the San Diego pocket mouse include Lake Mathews/Estelle Mountain/Gavilan Hills, the Badlands, Potrero Valley, Domenigoni Valley, Cactus Valley, Crown Valley, the Sage/Vail Lake area, Aguanga, Santa Rosa Plateau, and the Anza Valley. It has been observed in at least 13 of 22 reserve/public ownerships and has high potential to occur in the remaining nine (based on the current mapping of reserves/public ownerships). Existing reserves/public ownerships that provide substantial habitat for this species include the core Stephens' kangaroo rat reserves: Lake Skinner core reserve, Lake Mathews core reserve; San Jacinto core reserve, Motte-Rimrock core reserve, and Sycamore Canyon core reserve. Other key public ownerships that provide habitat for the species include the Santa Rosa Plateau Reserve, Box Springs Mountain Park, Kabian Park, and Santa Margarita Ecological Reserve.
Throughout the Plan Area in sage scrub, grasslands, and chaparral.
Genetics: The northwestern San Diego pocket mouse (P. f. fallax) is one of six subspecies of San Diego pocket mouse (Williams et al. 1993). The diploid chromosome number of the San Diego pocket mouse is 44 (Patton and Rogers 1993a). Based on protein electrophoresis, the San Diego pocket mouse shows a moderate level of genetic heterozygosity (4-7 percent), and is similar to other non-heteromyid rodents, which typically are heterozygous at between 4 and 5 percent of their allozyme loci (Patton and Rogers 1993b). It is unclear, however, whether this observed heterozygosity reflects true genetic variation or is an artifact of the choice of proteins that were selected for analysis (Patton and Rogers 1993b).
Diet and Foraging: Like other desert-adapted heteromyid rodents, the San Diego pocket mouse primarily is a granivore (seed eater). In a study of a rodent community in Irvine, Orange County, Meserve (1976) determined that the diet of the San Diego pocket mouse consisted almost purely of seeds during the autumn and early winter. The pocket mouse harvested seeds of the shrubs Eriogonum, Rhus, and Artemisia in the winter and spring, and then returned to grass seeds in the summer. Herbaceous forbs and green grasses were seldom utilized except in the latter part of the spring. Insects also were taken.
Beyond specialization on seeds, little is known of the foraging behavior of the San Diego pocket mouse. However, Reichman and Price (1993) provide a comprehensive treatment of heteromyid foraging that probably is generalized to the San Diego pocket mouse. Pocket mice possess external, fur-lined cheek pouches that promote collecting and caching of seeds either in scatter- or larderhoards, but it is not known which pattern the San Diego pocket mouse exhibits. Pocket mice (Chaetodipus, Perognathus) tend to forage under shrub and tree canopies, or around rock crevices, in contrast to kangaroo rats (Dipodomys ssp.) and kangaroo mice (Microdipodops spp.) that tend to forage in more open areas (Reichman and Price 1993). The reliable occurrence of different species in different microhabitats is well documented, but reasons for these microhabitat preferences are not well understood (Reichman and Price 1993). Factors such as interspecific competition, foraging economics, and predation risk probably are important factors in microhabitat selection, but the mechanisms and functions of such selection are not known. An interesting laboratory study of microhabitat selection conducted by Price and Longland (1989) demonstrated that San Diego pocket mice tend to select artificial patches with aggregated seeds in light (vermiculite) soils. They suggest that San Diego pocket mice encounter similar habitats in the wild.
Daily Activities: Little is known of the specific daily activities of the San Diego pocket mouse, but heteromyids primarily are nocturnal, with peaks of activity shortly after dusk and again before dawn (Reichman and Price 1993). The time and temporal pattern of surface activity probably relates to the availability of food resources, predation risk, energy costs, and other important activities (e.g., breeding), but nothing is known of these dynamics in the San Diego pocket mouse. During the day, pocket mice remain in their day burrows. As described above, pocket mice tend to select microhabitats with shrub or tree canopy cover or rocky areas for nocturnal foraging bouts. The association of the San Diego pocket mouse with sage scrub and chaparral and rocky and gravelly substrates is consistent with this generalization.
McClenaghan (1983) suggests that the San Diego pocket mouse may become torpid (dormant) during periods of cold weather, but a review of the physiological ecology literature for heteromyids by French (1993) indicates that the San Diego pocket mouse probably only engages in short bouts of torpor during times of energetic emergency and can only tolerate body temperatures down to 10-15 Celsius. Because this species inhabits a relatively mild, coastal environment, it probably forages on the surface year-round. It has been trapped on the surface in all months (Bleich 1973). (See discussion of physiological ecology below for more complete treatment.)
Reproduction: There is little information regarding the reproduction of the San Diego pocket mouse, and the few studies that have been conducted were of relatively short duration. McClenaghan (1983) and Bleich (1973) both noted seasonal reproduction in the San Diego pocket mouse, with peak activity in the spring and early summer. McClenaghan conducted a two-year study of the San Diego pocket mouse in Jacumba in extreme southeastern San Diego County (possibly C. f. pallidus) and found that 55 percent to 100 percent of the individuals were in reproductive condition in the spring. Reproductive condition was temporally correlated with peak herbaceous plant production. McClenaghan also noted an earlier onset of breeding in the milder of the two winters, but the duration of the study was too short to draw valid conclusions about this relationship.
Like other heteromyids, the San Diego pocket mouse likely has a relatively low reproductive output. According to data summarized by Jones (1993), the typical litter size of the San Diego pocket mouse is four pups and the gestation period is about 25 days. Nothing is known of the number of litters produced per year, the timing of weaning or reproductive potential of young-of-the-year. However, most heteromyids show flexible reproductive strategies, with the capacity to produce at least two litters in good years and with females capable of breeding in their natal season, while on the other hand, foregoing reproduction altogether in poor years (e.g., see Jones 1993 for discussion of life history traits). It is expected that the San Diego pocket mouse employs similar reproductive flexibility.
Survival: The only information regarding survival of the San Diego pocket mouse in the wild is from McClenaghan (1983). In a two-year study in Jacumba in San Diego County, McClenaghan recorded an average survival on his study site of 5.2 months, with 18 months as the longest observed survival. The average monthly survival rate was 0.77 and no sex difference was observed. It should be noted, however, that these data do not separate disappearances from the study site due to mortality and emigration. The San Diego pocket mouse is known to survive in captivity up to 8 years (Jones 1982 as cited in Nowak 1991). This observed longevity is consistent with other heteromyids (Jones 1993).
Dispersal: In a review of Jones' (1993) discussion of dispersal pattens of heteromyids, no data were found concerning dispersal of the San Diego pocket mouse and there were very limited data for other pocket mouse species. Based on the data available, a conservative assumption is that pocket mice do not disperse great distances. Jones (1993) cites work demonstrating that while in one study 25-30 percent of Chaetodipus formosus made dispersal movements greater than 500 feet, in another study of the same species only 5 percent of the individuals shifted home ranges, and in a third study recapture rates were 62 percent for males and 55 percent for females (high recapture rates indicate relatively sedentary behaviors).
Socio-Spatial Behavior: Very little is known of the socio-spatial behavior of the San Diego pocket mouse. MacMillen (1964; as cited by Jones 1993) reported little intrasexual (i.e., male-male and female-female) home range overlap, but there was evidence of intersexual range overlap. Average home ranges were reported by MacMillen to be 0.36 ha (0.9 acre) for males and 0.25 ha (0.6 acre) for females.
Community Relationships: The community ecology of heteromyid rodents, including pocket mice (Perognathus and Chaetodipus spp.), kangaroo rats (Dipodomys spp.), and kangaroo mice (Microdipodops spp.) is among the most studied aspect of this family's biology. Brown and Harney (1993) provide a comprehensive overview and attempted synthesis of this complex subject. Some generalizations that fall from this large body of literature are presented here.
Arid grassland and desert environments support a surprising diversity of coexisting rodent granivores. The diversity and number of coexisting species vary depending on local conditions and the requirements of the constituent species. The San Diego pocket mouse in western Riverside County probably overlaps with at least four kangaroo rat species (D. agilis, D. merriami, D. stephensi and D. simulans), two other pocket mice ( Chaetodipus californicus and Perognathus longimembris), and at least six native murids (Peromyscus maniculatus, P. eremicus, P. californicus, Neotoma lepida, N. fuscipes, and Reithrodontomys megalotis) that potentially compete for space and food resources. Brown and Harney (1993) conclude that "the composition of these assemblages is not random. Instead it is determined by interactions of the species with the physical environment, with other kinds of organisms, and with other rodent species." page 646. Generally, species that do coexist tend to occupy and exploit different microhabitats or niches or differ in their seasonality of resource exploitation.
Interspecific competition is an important component of the organization of heteromyid community structure. For example, competitive exclusion can result in nonrandom assemblages that partition the resources and habitats in the community. Other potential mechanisms of resource partitioning listed by Brown and Harney (1993) include habitat selection or restriction, independent adaptations, food partitioning and variable foraging efficiency, seed distribution, resource variability, predator-mediated coexistence, aggressive interference, and seasonality.
Pocket mice and other heteromyid rodents also modify their environments (Brown and Harney 1993; Price and Jenkins 1986). They dig burrows, which moves the soils and provides habitat and refugia for other species, including other rodents, reptiles, amphibians, birds and invertebrates. Collection, storage and consumption of seeds by kangaroo rats, for example, have profound effects on the vegetation structure of the habitats they occupy (Price and Jenkins 1986). In addition, resource use by pocket mice and kangaroo rats substantially overlaps with that of seed-eating birds and harvester ants. However, in a literature review of effect of granivorous rodents on the plant community, Price and Jenkins (1986) cautioned against drawing broad generalizations because specific effects will be affected by competitor densities, climate and edaphic conditions, rodent densities, seed preferences, and caching behavior.
The coevolutionary results of such inter- and intraspecific community relationships and their relationship to plant communities are not understood, but it can be concluded that rodents are an important component of arid ecosystems. In addition to their direct impacts on plant communities, they are important prey for a variety of predators and their presence also affects populations of other prey such as small reptiles, lagomorphs and some birds (Brown and Harney 1993).
Physiological Ecology: Pocket mice and most other heteromyid species live in arid environments characterized by hot summers, long, cold winters, unpredictable precipitation, and ephemeral primary productivity of food sources (French 1993). Although the San Diego pocket mouse lives in a relatively mild coastal climate compared to many other heteromyid species, it still is subject to periods of fairly extreme cold, heat, and drought. As described above, the San Diego pocket mouse is active year-round, but may enter short periods of torpor during cold periods, but not to the deep level of the little pocket mouse (Perognathus longimembris); they can only tolerate body temperatures down to 10-15o Celsius and for periods less than 24 hours.
As with several other desert-adapted heteromyid species, the San Diego pocket mouse apparently does not require exogenous (i.e., drinking) water (French 1993); they can utilize water produced during oxidative metabolism. Compared to non-heteromyids, the San Diego pocket mouse and other heteromyids have low rates of evaporative water loss, accomplished by a reduction in both respiratory and cutaneous water losses (French 1993). The San Diego pocket mouse also has relatively high urine concentration levels (i.e., powerful kidneys) similar to those recorded for the hot desert species Merriam's kangaroo rat (Dipodomys merriami) and Sonoran Desert pocket mouse (Chaetodipus penicillatus) (French 1993). Other water-conserving mechanisms demonstrated in heteromyids and other rodents, but not specifically documented for the San Diego pocket mouse, are low water content in fecal matter, highly concentrated milk, and reingestion of the feces of young (allocoprophagy) and their dilute urine. Anecdotally, the fecal pellets of the San Diego pocket mouse collected from traps appear to be very dry compared to murid rodents such as deer mice, harvest mice, and woodrats (Behrends, pers. obs.).
Pocket mice and other heteromyids also reduce energy needs by having basal metabolic rates (metabolism at rest) about one-third lower than those of average mammals. This, in combination with hoarding food during productive periods, allows pocket mice to endure periods of scarce food.
Other potential behavioral adaptations for maintaining water balance, energy, and thermoneutrality are remaining in day burrows during periods of climatic extremes, plugging burrow entrances to retain moisture (i.e., humidity) in the burrow, moving vertically and horizontally within burrow systems in relation to soil temperatures, and ingestion of herbaceous and succulents plants (possibly to support lactation).
Habitat Fragmentation and Isolation: The San Diego pocket mouse appears to be sensitive to habitat fragmentation and degradation. Bolger et al. (1997) studied rodent diversity and abundance in isolated habitat fragments of varying size and age in San Diego County. The San Diego pocket mouse tended to occur in habitat patches with 90-100 percent shrub cover, with only two of eight occupied patches having shrub cover of 50 percent and 75 percent. Bolger et al. tentatively concluded that canyon fragments under 25 ha (61.8 acres) and isolated for more than 30 years support few populations of native rodents, including the San Diego pocket mouse. Their data also suggest that isolated habitat patches must be at least 25 ha (62 acres) to 80 ha (198 acres) to sustain native rodent populations.
Disease: There is little information on the endo- and ectoparasites and associates carried by the San Diego pocket mouse. Whitaker et al. (1993) report that one species of mite (Androlaelaps frontalis), 15 species of chiggers (Dermadelema, Euschoengastia, Hexidionis, Hyponeocula, and Otorhinophila), and one species of flea (Meringis dipodomys) have been recorded from the San Diego pocket mouse.
Little is known of the life history traits of the San Diego pocket mouse and more research is desirable. However, this species is still relatively common in sage scrub, chaparral, and grassland habitats throughout the MSHCP Plan Area. Conservation of this species can be accomplished at a landscape level; i.e., conservation of large blocks of connected habitat throughout the Plan Area should be adequate for this species. Based on the Bolger et al. study, however, blocks of habitat of at least 200 acres will be needed to conserve this species at a given location.
Bleich, V.C. 1973. Ecology of rodents at the United States Naval Weapons Station Seal Beach, Fallbrook Annex, San Diego County, California. M.A. Thesis, California State University, Long Beach, 102 pp.
Bolger, D.T., A.C. Alberts, R.M. Sauvajot, P. Potenza, C. McCalvin, D. Tran, S. Mazzoni, and M.E. Soulé. 1997. Responses of rodents to habitat fragmentation in coastal southern California. Ecological Applications 7:552-563.
Brown, J.H. and B.A. Harney. 1993. Population and community ecology of heteromyid rodents in temperate habitats. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 618-651.
Chase, M.K., W.B. Kristan III, A.J. Lynam, M.V. Price, and J.T. Rotenberry. 2000. Single species as indicators of species richness and composition in California coastal sage scrub birds and small mammals. Conservation Biology 14:474-487.
French, A.R. 1993. Physiological ecology of the heteromyidae: economics of energy and water utilization. In Genoways, H.H. and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10, The American Society of Mammalogists, pp. 509-538.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Jones, T. 1993. Social systems of heteromyid rodents. In Genoways, H.H. and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10, The American Society of Mammalogists, pp. 575-595.
Lackey, J.A. 1996. Chaetodipus fallax. Mammalian Species 517:1-6. Published by the American Society of Mammalogists.
McClenaghan, L.R. Jr. 1983. Notes on the population ecology of Perognathus fallax in southern California. The Southwestern Naturalist 28:429-436.
Mearns, E.A. 1901. A new pocket mouse [sic] from southern California. Biological Society of Washington 14:135-136.
Meserve, P.L. 1976. Food relationships of a rodent fauna in a California coastal sage scrub community. Journal of Mammalogy 57:300-319.
Metropolitan Water District (MWD) and Riverside County Habitat Conservation Agency (RCHCA). 1995. Lake Mathews Multiple Species Habitat Conservation Plan and Natural Community Conservation Plan: Volume 2.
Nowak, R.M. 1991. Walker's Mammals of the World. Fifth Edition. The Johns Hopkins University Press, Baltimore. 1629 pp.
Montgomery, Steve. 31 August 1998. Personal fax communication to the U.S. Fish and Wildlife Service.
Patton, J.L. and D.S. Rogers. 1993a. Cytogenics. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 236-258.
Patton, J.L. and D.S. Rogers. 1993b. Biochemical genetics. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 269-269.
Price, M.V. and S.H. Jenkins. 1986. Rodents as seed consumers and dispersers. In Seed Dispersal, Academic Press, Australia, pp. 191-235.
Price, M.V. and W.S. Longland. 1989. Use of artificial seed patches by heteromyid rodents. Journal of Mammalogy 70:316-322.
Price, M.V. and N.M. Waser. 1984. On the relative abundance of species: postfire changes in a coastal sage scrub rodent community. Ecology 65:1161-1169.
Reichman, O.J. and M.V. Price. 1993. Ecological aspects of heteromyid foraging. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 539-574.
Whitaker, J.O. Jr., W.J. Wrenn, and R.E. Lewis. 1993. Parasites. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 386-478.
Williams, D.F., H.H. Genoways, and J.K. Braun. 1993. Taxonomy. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No. 10 of the American Society of Mammalogists, pages 38-196.
San Bernardino flying squirrel (Glaucomys sabrinus californicus)
State: Species of Special Concern
Federal: None
Habitat for the San Bernardino flying squirrel in the Plan Area only occurs in the San Jacinto Mountains, primarily on U.S. Forest Service (USFS) lands in the San Bernardino National Forest (SBNF) and the Mt. San Jacinto Wilderness State Park. Suitable habitat also is present on private inholdings within the SBNF in the San Jacinto Mountains . The status (e.g., abundance, distribution, reproduction) of this species is not well understood within the Plan Area. Therefore, habitat assessments, population baseline information, long-term monitoring studies, and adaptive management are necessary. The San Bernardino flying squirrel is a Group 3 species because it has a narrow distribution in the Plan Area and requires site specific monitoring.
Conservation of the San Bernardino flying squirrel in the San Jacinto Mountains is largely dependent on activities on Forest Service lands, but activities in the State Park and private ownerships within the SBNF also will be important to conservation of the species. As a Forest Service Sensitive Species, the flying squirrel is protected through implementation of Forest plans and the biological evaluation (BE) process, which assesses the potential effects of Forest Service activities on the species.
Due to absence of information regarding abundance, distance and life history requirements, incidental take of this species is not included in this permit until conservation of the species in the Plan Area has been demonstrated by achieving Objective 2 below.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 19,476 acres (67 percent) of suitable montane coniferous forest and deciduous woodland and forest habitats within the San Jacinto Mountains Bioregion for breeding, foraging, wintering, and dispersal movement.
Within the MSHCP Conservation Area, confirm occupation of 1000 ha (2470 acres) with a mean density of at least 2 individuals per hectare (2 individuals per 2.47 acres) in the San Jacinto mountains; and in the San Bernardino Mountains confirm occupation of 100 ha.
This conservation analysis focuses on suitable habitat for the San Bernardino flying squirrel in the San Jacinto Mountains bioregion. Although flying squirrels appear to be more common in the San Bernardino Mountains, of which a small portion is in the extreme northern part of the Plan Area, work on spotted owls by LaHaye, and specifically owl pellet analyses, has revealed no evidence of flying squirrels within the portion of the San Bernardino Mountains located in the Plan Area (W. LaHaye, pers.comm. 2002). However, LaHaye did find evidence of flying squirrel occupation just north of the Plan Area boundary.
While approximately 68 percent of suitable habitat is in public ownership and 31 percent is in private ownership within the Plan Area, too few recent records for the species are available to identify core habitat areas at this time. Therefore, the conservation analysis is landscape-based and assumes implementation of the comprehensive surveys, conservation and management actions described above.
For the purpose of the conservation analysis, potential habitat for the San Bernardino flying squirrel includes broad-leaved upland forest, mixed evergreen forest, montane riparian forest and the various coniferous forest mapping units (Jeffrey pine, lodgepole pine, lower montane coniferous forest, southern California white fir and subalpine coniferous) in the San Jacinto Mountains bioregion. Based on these assumptions about habitat, the Plan Area supports approximately 28,880 acres of potential habitat for the flying squirrel.
Table 1 shows the conservation of potential habitat for the San Bernardino flying squirrel. Overall, approximately 19,476 acres (67 percent) of suitable habitat is in the MSHCP Conservation Area. Virtually no potential habitat is in the Criteria Area or in the rural mountainous designation areas.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
SAN BERNARDINO FLYING SQUIRREL
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Broad-leaved Upland Forest | 274 | 0 | 206 | 206 | 27 | 41 | 68 |
| Jeffrey Pine | 13,375 | 0 | 7,749 | 7,749 | 0 | 5,525 | 5,626 |
| Lodgepole Pine | 578 | 0 | 578 | 578 | 0 | 0 | 0 |
| Lower Montane Coniferous Forest | 6,070 | 0 | 3,592 | 3,592 | 0 | 2,478 | 2,478 |
| Mixed Evergreen Forest | 4,467 | 0 | 3,915 | 3,915 | 0 | 552 | 552 |
| Montane Riparian Forest | 218 | 4 | 180 | 184 | 1 | 33 | 34 |
| So. California White Fir | 3,871 | 0 | 3,225 | 3,225 | 0 | 646 | 646 |
| Subalpine Coniferous | 27 | 0 | 27 | 27 | 0 | 0 | 0 |
| TOTAL | 28,880 | 5 <1% |
19,472 67% |
19,476 67% |
28 <1% |
9,275 32% |
9,404 33% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
It should be understood that the San Jacinto population of the San Bernardino flying squirrel is physically isolated from other populations in the San Bernardino Mountains by the Banning Pass (Hall 1981). Also, because little is known of the distribution of the San Bernardino flying squirrel in the San Jacinto Mountains, little can be said about reserve configuration issues other than what can be generalized from research on this species in other geographic regions.
Home ranges of flying squirrels are relatively large. Wells-Gosling and Heaney (1984) reviewed data suggesting that an individual squirrel required 31 ha (76 acres) of "optimum" habitat in Alaskan taiga. In other studies, home ranges have been estimated to range from 3 ha (7.5 acres) to 12 ha (30 acres) by various measurement methods and statistical analyses (e.g., live-trapping and inclusive boundary strip calculation, radiotelemetry and minimum convex polygon calculation). (Because home range estimates are "assumption-laden" relating to observation methods and statistical techniques, it is best for conservation planning to state ranges and assume the larger range values reflect minimum habitat areas.). It has been suggested that the availability of nest sites and food resources also limits the population density and distribution of flying squirrels. Flying squirrels tend to occur in higher densities in old growth forest (Ransome and Sullivan 1997; Witt 1992; Waters and Zabel 1995). Waters and Zabel found that flying squirrel density was positively correlated with frequency of hypogeous (subterranean) sporocarps in their diet.
These spatial parameters and habitat requirements suggest that a viable population of the flying squirrel probably requires a large, interconnected habitat area, ideally with large patches of old growth forest, but that actual locales supporting squirrels will be related to the distribution of important microhabitats (i.e., nest cavities and food patches). Flying squirrels generally travel from tree to tree during foraging, but also occasionally on the ground (Wells–Gosling and Heaney 1984). While squirrels appear to prefer old growth forest, they are known to use second growth forest, and the latter may be essential to dispersal (although dispersal is poorly understood).
The San Bernardino National Forest south of the Banning Pass combined with the Mt. San Jacinto Wilderness State Park in the Plan Area provides a large, relatively contiguous block of habitat for the flying squirrel. There is existing habitat fragmentation in the communities of Pine Cove, Idyllwild and Mountain Center, but there is still a large, intact block of habitat remaining generally northeast of Idyllwild and east of Highway 243. If this species still occurs in the Plan Area, it should be possible to conserve and manage habitat to maintain the population.
In summary, conservation of the San Bernardino flying squirrel will be achieved by inclusion of approximately 19,476 acres (67 percent) of suitable Conserved Habitat in the San Jacinto Mountains Bioregion of the MSHCP Conservation Area.
About 9,404 acres (33 percent) of suitable habitat in the San Jacinto Mountains Bioregion is on private ownerships outside of the MSHCP Conservation Area. This suitable habitat is on private lands in the areas of Pine Cove, Idyllwild, Mountain Center, Hemet Lake and various other private inholdings within the forest. Any proposed Incidental Take of habitat on USFS or State Park lands would be consistent with approved activities for those lands.
The point data for the San Bernardino flying squirrel in the MSHCP database are relatively poor, with only eight total records and all having a precision codes of "4," meaning that the location is very imprecise or vague, or was plotted as a general location. Five of the records are quite dated (1908, 1915, 1916) and three area relatively recent (1987, 1993, 1995).
With regard to general life history information, there are relatively few studies of the flying squirrel beyond general habitat associations, diet, home range and reproductive behavior. There are no studies of physiological ecology nor detailed studies of community ecology. There are no specific studies of the subspecies San Bernardino flying squirrel (G. s. californicus).
Throughout their extensive continental range, northern flying squirrels (Glaucomys sabrinus) inhabit a wide variety of woodland habitats primarily consisting of conifers, mixed coniferous-deciduous forest and occasionally broad-leaf-deciduous forest (Ransome and Sullivan 1997; Wells-Gosling and Heaney 1984; Witt 1992). Flying squirrels primarily inhabit old growth forests, but also are found in second growth stands (Ransome and Sullivan 1997; Witt 1992). Doyle (1990) found similar abundances of flying squirrels in riparian and upland areas of montane forests, although juveniles tended to be more common in uplands and breeding adults more common in riparian areas. In the central Sierra Nevada, tree species in habitats occupied by the flying squirrel include white fir (Abies concolor), red fir (A. magnifica), lodgepole pine (Pinus contorta), Jeffrey pine (P. jeffreyi), and western white pine (P. monticola). Habitats in western Oregon are dominated by western fir (Pseudostuga menziesii) and western hemlock (Tsuga heterophylla). According to Holland (1986), the San Jacinto Mountains contain several intergrading associations of conifer forests, including Jeffrey pine-fir forest, Southern California white fir forest, lodgepole pine forest, and western Ponderosa pine forest. Common fir and pine species in the San Jacinto Mountains include white fir, coulter pine (P. coulteri), Jeffrey pine, sugar pine (P. lambertiana), and Ponderosa pine (P. ponderosa) (San Jacinto Mountains Digital Library 2000).
Nesting or den sites of northern flying squirrels are variable. Den sites in Alaska include cavities in trees (USFWS 1991) and "witches brooms," which are abnormal clumps of branches caused by tree rust diseases (Alaska Department of Fish and Game [ADFG] 1994). In Alaska, individuals nest in tree cavities approximately 25 feet above the ground (range 5-45 feet) (ADFG 1994). Throughout the species' range, predominant nest sites appear to be tree cavities, but they may also construct and use leaf nests in the summer (USFWS 1991). In northern Idaho, flying squirrels construct nests of dried grass lined with lichens and fastened to trees (Wells-Gosling and Heaney 1984).
The species G. sabrinus occurs throughout boreal (northern) forests from Alaska in the northwest, across Canada to Labrador in the northeast, south to Tennessee in the east and south to disjunct populations (G. sabrinus californicus) in the San Bernardino and San Jacinto mountain ranges (Hall 1981) in the west. Relatively little is known about the distribution of habitat actually occupied by the San Bernardino flying squirrel in southern California. Within the San Bernardino Mountains in the Big Bear area, flying squirrels were trapped in 1990 and apparently again in1998 on the west side of Bear Mountain, Barton Flats, Deer Canyon and Little Green Valley (USFS 1995; Driessen et al. 1998 [this study was vague as to specific location of trapping, but appears to be same areas as 1990 study]). Spotted owl pellet analyses by LaHaye also has revealed evidence of flying squirrel occupation in this portion of the San Bernardino Mountains Range (W. LaHaye, pers. comm. 2002).
Historic and recent locations of individuals of the San Bernardino flying squirrel in the Plan Area include the Idyllwild area along Highway 243, west of Pine Cove, Strawberry Creek west of Idyllwild, and near Apple Creek north of Lake Hemet. Seven of the eight locations occur on private lands, but most of the potential habitat probably is on USFS land.
Population data are too few to specify localities in the San Jacinto Mountains, but the flying squirrel is known from both USFS lands and private inholdings in the San Jacinto Mountains Bioregion. Although the species apparently is more common in the San Bernardino Mountains (USFS 1995; LaHaye, pers. comm. 2002), it is not known in the Plan Area portion of the San Bernardino Mountains, which mostly includes the south-facing foothills of the range above Cherry Valley and Banning/Beaumont. If the species is extant in the Plan Area, it would only occur in the San Jacinto Mountains.
Virtually nothing is known of the specific biology and habits of the sub-species San Bernardino flying squirrel. The review of the biology of the species provided here is for various other subspecies inhabiting different regions, primarily the Sierra Nevada and Cascade ranges of northern California and Oregon, British Columbia, and Alaska. Thus, the life history traits and ecological relationships reported here are only suggestive of those relevant to the San Bernardino flying squirrel.
Genetics: The San Bernardino flying squirrel is one of 25 subspecies of northern flying squirrel (Hall 1981). Range maps of most of the subspecies indicate relatively continuous geographic ranges of the various subspecies, but the San Bernardino flying squirrel is depicted as a disjunct population separated from the southern Sierra Nevada by the Mojave Desert. Furthermore, the populations in the San Bernardino and Jacinto mountain ranges are themselves geographically isolated by the Banning Pass. Thus, the San Jacinto population functionally is an island population. There is no scientific literature that addresses genetic diversity within the species, but it can be expected that a relatively small population of the flying squirrel such as that in the San Jacinto Mountains is subject to the effects of genetic drift, which can result in inbreeding depression from loss of heterozygosity or fixation of a deleterious gene, random changes in phenotypes, and a decrease in genetic variance (Franklin 1980). Anyone or combination of these effects may increase the chance of local extinction. Furthermore, it would be expected that the San Bernardino Mountain and San Jacinto Mountain populations, through evolutionary mechanisms such as genetic drift and differential selection pressures, would ultimately diverge into separate subspecies.
Diet and Foraging: Most studies indicate that fungi and lichens are primary food sources for the northern flying squirrel (Hall 1991; Maser et al. 1985; Ransome and Sullivan 1997; Waters and Zabel 1995; Witt 1991). Flying squirrels also are known to eat certain seeds, buds, fruit, staminate cones, insects, and other mammal material (McKeever 1960). Hall (1991) examined stomach and fecal samples of flying squirrels in the central Sierra Nevada and found that hypogeous (subterranean) fungi were most common, followed by puffballs, lichens, and gill fungi. Common fungi genera in their diets were Gautiera, Rhizopogon, and Geopora regardless of season. Lichens that grow on the bark of conifers were collected more frequently during snow cover. Witt (1991) suggests that basidiomycete fruit (mushrooms, toadstools, puff balls, rusts, and smuts) available in the autumn provide biomass and energy for physiological maintenance and fat deposition for the winter months. Fungi may be cached in tree cavities for the winter. Flying squirrels may obtain free water from their foods, rain, dew, and snow, and perennial water sources do not appear be a critical habitat requirement (ADFG 1994).
Daily Activities: Northern flying squirrels primarily are nocturnal and show a biphasic activity pattern in the summer (Wells-Gosling and Heaney 1984; Witt 1992). Using radiotelemetry, Witt (1992) found that squirrels in western Oregon old growth forest typically begin foraging approximately one hour after sunset, forage for three to four hours, return to their dens, and then emerge for another three- to four-hour foraging bout. In Alaska, flying squirrels have been observed to travel as far as 1.2 miles in a night and be away from their den for as long as seven hours (ADFG 1994). As their name suggests, they primarily move by gliding from tree to tree, but they also travel on the ground (Wells-Gosling and Heaney 1984).
Reproduction: Reproduction and breeding season appear to vary geographically, and may reflect physiological and/or behavioral adaptations to local climatic and environmental conditions. In Alaska, the peak breeding season is March to late June, depending on the length and severity of the winter (ADFG 1994). In the southern Appalachian, breeding occurs in the early spring (USFWS 1991). On the other hand, Witt (1991) found that breeding in western Oregon tended be in the summer months based on captures of juveniles less than 70 days old in autumn and observations of lactating females in August. The flexibility in timing of reproduction by flying squirrels is further evidenced by the record of a 16-18 day old juvenile in December (Witt 1991).
The number of litters produced per year probably also varies geographically. Muul (1969) recorded two litters of two to six young per litter per year, and a gestation period of 37-42 days. In the Appalachians, it appears that females produce one litter. In Alaska, one litter of two offsprings per year is typical (ADFG 1994). Young are fully grown by 240 days and females are reproductively mature by 11 months (ADFG 1994). Adult weights range from 95 to 175 g (ADFG 1994; Ransome and Sullivan 1997; USFWS 1991; Witt 1991). Sexual dimorphism size is not apparent, but sizes vary substantially geographically (Wells-Gosling and Heaney 1984). Females raise their litters without the help of males, but defense of dens against males and other females has not been observed (Madden 1974).
Habitat quality also may be a factor in the reproductive behavior of the flying squirrel. Doyle(1990) recorded more breeding males and females in riparian habitats than upland areas and suggested that upland habitats may be sinks where survivorship and reproduction are lower.
Survival: There are little data on survival by flying squirrels. In Alaska, the annual mortality rate is about 50 percent for one- and two-year-old squirrels (ADFG 1994), few individuals live more than four years (Wells-Gosling and Heaney 1984), and complete population turnover can occur in three years (ADFG 1994).
Dispersal: Northern flying squirrels appear to live in family groups of adults and juveniles at least outside the breeding season, are relatively gregarious, and known to share nests (USFWS 1991). This suggests that the species is philopatric (remaining in their natal range). However, Doyle (1990) recorded more juveniles than adults in upland habitat compared to riparian habitat in the Cascade Range, suggesting that juveniles are dispersing in this region. There are too little data to drawn conclusions about dispersal behavior and dispersal requirements for this species.
Socio-Spatial Behavior: The socio-spatial behavior of the northern flying squirrel is not well understood. As described above, flying squirrels appear to be relatively gregarious and live in family groups outside the breeding season, but the function and dynamics (e.g., seasonality) of their social structure in relation to foraging, reproduction, dispersal, and physiological ecology are not known. In studies utilizing feeding stations, adults dominate younger squirrels, but subadults share food. Aggression at feeding stations occurred occasionally, but was short-lived (Wells-Gosling and Heaney 1984).
It appears that northern flying squirrels have substantial home range overlap. For example, Wells-Gosling and Heaney (1984) reviewed data suggesting that in Alaskan taiga, each individual required 31 ha of "optimum" habitat and that ranges overlapped. Also, it is reported that two to six different individuals can be trapped in a 300 x 400 meter area (12 ha) (USFWS 1991) and flying squirrels in Alaska may use as many as 13 different den trees within 19.8 acres (8 ha). Home ranges of northern flying squirrels typically are on the order of 3 to 12 ha (ADFG 1994; Witt 1992). Witt (1992) calculated home ranges in western Oregon of 3.7 to 4.2 ha using live-trapping and the inclusive boundary strip calculation method, and ranges of 3.4 to 4.9 ha using radiotelemetry and the minimum convex polygon method of calculation. Based on live-trapping, Ransome and Sullivan (1997) reported average movements between trap sessions of 66-78 meters and maximum distances of 79-94 meters in British Columbia. But, as reported by the ADFG (1994), squirrels in Alaska can move at least 1.2 miles in a night. This information suggests that northern flying squirrels tend to be sedentary over long periods of time, but that their nightly moves can be extensive.
Ransome and Sullivan (1997) reported a density range of 0.35 squirrels/ha to 1.03 squirrels/ha in second growth and old growth forest, respectively, in British Columbia. Witt (1992) found much lower densities in western Oregon, with mean densities of 0.12 squirrels/ha in second growth forest and 0.85 in old growth forests. Waters and Zabel (1995) recorded densities in northeastern California ranging from 0.31 squirrels/ha in logged shelterwood stands to 3.29 squirrels/ha in old stands. Witt (1992) reported that other studies have found densities of 0.2 to 1.8, 1.2 to 2.1 and 0.2 to 2.1 squirrels/ha. There is some evidence that population densities are correlated with the availability of food. Waters and Zabel (1995) found that flying squirrel density was positively correlated with the frequency of hypogeous sporocarps in their diet ®= 0.86, but not with cavity density or understory cover in their habitat. Similarly, Ransome and Sullivan (1997) found that squirrel densities were 1.8 times higher in treatment patches supplemented with sunflower seeds; however, the proportion of adults in breeding condition was not related to the food supplementation treatment.
Community Relationships: In the western portion of the flying squirrel's geographic range, there is little information about community relationships. In the eastern portion of its range, where it overlaps with the southern flying squirrel (G. volans), there is evidence of direct competitive relationships with the more aggressive southern flying squirrel. Southern flying squirrels may force northern flying squirrels into conifer forest with fewer nesting sites (Weigl 1978). It can be expected that any overlapping species that are hole or cavity nesters could be potential competitors for nesting sites. In the San Jacinto Mountains, potential competitors include western gray squirrel, several woodpeckers, swallows, purple martins, and small rodents. However, there are no data for the San Bernardino flying squirrel directly addressing possible competitive relationships with other species.
Northern flying squirrels are prey for a number of species, including California spotted owl, great horned owl, barn owl, goshawk, red-tailed hawk, marten, wolf, lynx, weasel, foxes, and house cats (ADFG 1994). The northern flying squirrel is the primary prey of the northern and California spotted owls throughout much of their range (Waters and Zabel 1995) and a pair of spotted owls can consume about 500 squirrels per year (Wells-Gosling and Heaney 1984). Flying squirrels are a documented prey item in spotted owl diets in the San Bernardino Mountains (W. LaHaye, pers. comm. 2002), but whether this species is important prey for any particular predator in the San Jacinto Mountains is unknown. However, it seems unlikely because of the squirrel's apparent low density in the San Jacinto Mountains.
Flying squirrels also may play an important role in forest regeneration because they disperse spores of fungi that are dependent on animals digging them up (ADFG 1994). Squirrels consume the spores and disperse them in fecal material. Through this dispersal mechanism, northern flying squirrels may help inoculate disturbed areas such as clear cuts and burns with mycorrhizae that are symbiotic with plant roots, improving their ability to absorb nutrients and maintain health (ADFG 1994).
Physiological Ecology: The northern flying squirrel is adapted to a wide variety of environmental and climatic conditions, suggesting that they may have relatively broad habitat tolerances due to physiological (metabolic processes) or behavioral (social aggregation during cold periods) mechanisms. In Alaska, in the coldest parts of winter, they aggregate with two or more individuals and enter torpor (ADFG 1994), but there is no published literature of systematic studies of their physiological ecology or evidence that they hibernate in the winter. They may not enter torpor at all in warmer climates (Wells-Gosling and Heaney 1984). Wells-Gosling and Heaney (1984) also cite observations of flying squirrels being active in the winter at temperatures as low as -24o Celsius and tracks are often seen in the snow.
Direct Threats. Because of the poor database, known threats to the San Bernardino flying squirrel cannot be identified. There are too little data on distribution and ecology for the subspecies in the San Jacinto Mountains to determine whether ongoing specific activities are directly or indirectly affecting the population, or whether planned activities will have an effect in the future. However, it can be assumed that threats include loss and fragmentation of habitat, timber and firewood harvesting, predation, lack of food resources, lack of tree cavities, fungi harvesting, and recreation. Flying squirrels also have been found entangled in barbed wire fencing (Wells-Gosling and Heaney 1984). The potential deleterious effects of air pollution on food resources (fungi and lichens) also are unknown.
Parasites also may be a threat to the northern flying squirrels. Wells-Gosling and Heaney's (1984) review of parasites indicates that the species carries many ectoparasites including fleas (Opisodasys pseudarctomys, Opisodasys versperalis, Epitedia faceta, Tarsophylla octodecimdentata coloradensis, Orchopeas howardii, Orchopeas caedens, Orchopeas nepos, Monopsyllus vison, and Megarthroglossus divisus exsecatus), lice (Hoplopleura trisponosa, Microphthirus uncinatus, and Neohaematopinus sciuropteri), and mites and ticks (Acaropsellina summersi, Camincheyletus glaucomys, Eucheyletia oregonensis, Haemogamasus ambulans, Haemogamasus reidi, Hirstionyssus occidentalis (=punctatus), Hyperlaelaps microti, Ixodes marxi, Ioxdes pacificus, and Neotrombicula microti). Endoparasites include roundworms (Nematoda: Citellinema bifurcatum, Syphacia thompsoni), tapeworms (Cestoda: Andrya sciuri, Catenotaenia pusilla, Moneococestus thomasi and Hymenandrya sp.) and protozoa (Eimeria dorneyi and Eimeria sciurorum). The effects of these parasites is unknown, but a case of the nematode (Strongeloides robustus) being passed from the southern flying squirrel, its natural host, to the northern flying squirrel was lethal.
Long-term Threats. Virtually nothing is known of the status, population size and distribution of the flying squirrel in the San Jacinto Mountains. It should be understood, however, that if a San Jacinto Mountain population exists, it may be demographically and genetically unstable (Franklin 1980), and without a direct connection to the population in the San Bernardino Mountains, the risk of local extinction may be relatively high despite all conservation efforts. For example, a devastating fire, such as the one that burned thousands of acres near Idyllwild in 1996, could reduce the local population to levels that are unsustainable.
Little is known of the distribution, habitat requirements, and biology of the San Bernardino flying squirrel in the San Jacinto Mountains. Elsewhere in the range of G. sabrinus there is some evidence that distributions and populations may be limited by the availability of old growth forests (Witt 1992) and food resources (fungi year round and arboreal lichens during the winter) (Ransome and Sullivan 1997; Waters and Zabel 1995). For a federally-listed subspecies, the Carolina northern flying squirrel (G. s. coloratus), it is suggested that the species has declined since the last ice age, leaving only high elevation islands of occupation in its southern geographic range (USFWS 1991). The isolated San Bernardino and San Jacinto mountain range populations appear to be remnant populations resulting from this natural warming trend. As discussed above, these populations are at a relatively high risk of extirpation due to habitat isolation, and demographic and environmental stochastic events. Management for this species may include translocation.
At least two limiting factors may be important for the San Bernardino flying squirrel: food availability and nesting cavities. Very little is known about either in the MSHCP Plan Area. Work by Doyle (1990) indicates that within montane forest, breeding individuals tend to occur in higher abundances in riparian habitats compared to upland habitats, and that juveniles generally are more common in upland habitats. Doyle suggests that riparian habitats may be superior habitats because of more water, forage, herbs, deciduous shrubs, mast, more stable temperatures, and more friable soils for digging. Upland habitats may function as sink habitats that are marginal or unstable. While sink habitats provide refuge for dispersing individuals, survivorship and reproduction may be lower.
In a Biological Evaluation for the Bear Mountain Ski Resort in the San Bernardino Mountains, the USFS (1995) summarized the results of several studies that are directly relevant to conservation planning for the flying squirrel. These studies address effects of patch sized and fragmentation and the ability of squirrels to move between patches. Rather than summarize the USFS evaluation, it is restated in full here.
Northern flying squirrels may also be particularly sensitive to fragmentation of their habitat. Rosenberg and Raphael (1984) studied the effects of fragmentation in northwestern California. They found frequency of occurrence of northern flying squirrels was positively correlated with size of the stand - with only one occurrence in a stand less than 49 acres (20 ha). Stands less than 49 acres were concluded to be nonviable as they lacked a full complement of vertebrate species. Approximately 75 percent of stands over 247 acres (100 ha) had flying squirrels.
Rosenberg and Raphael (1984) also found a significant negative correlation between frequency of occurrence of northern flying squirrels and percentage of insularity (percentage of stand perimeter surrounded by clearcut edge). Frequency of occurrence was approximately equal in stands with up to 75 percent insularity. A sharp decline occurred in stands with over 75 percent insularity. Thus, it appeared that degree of isolation or forested patches and the size of those patches dictated usability by flying squirrels.
The ability of northern flying squirrels to traverse open areas has not been extensively studies. Mowrey and Zasada (1982) conducted radio-tracking studies of northern flying squirrel movements and found a maximum gliding distance of about 155 ft (48 m) with a mean glide distance of 65 ft (19.7 m). The squirrels readily glided over 30-ft-wide (10 m) roads. Waters (pers.comm. 1992) noted glides of 100-ft (45 m) across level ground.
Mowrey and Zasada (1982) also concluded that 65 ft (20 m) openings between forested areas, with occasional openings 100-120 ft wide (30-40 m), do not impede movement for northern flying squirrels. In larger areas, scattered trees appear to aid movement. Waters (pers. comm. 1992) found northern flying squirrels use in a shelterwood cut thinned to approximately 14 trees per acre (55-ft [17 m] spacing between 100-ft tall [45 m] trees). Some squirrels roosted in shelterwood-logging stands but foraged in surrounding uncut forests. Corridors connecting habitat blocks (leave strips between cuts) should be a minimum of 98.4 ft (30 m) wide when openings were [sic] present on both sides of the corridor (Mowrey and Zasada 1982." page 7.
Alaska Department of Fish and Game 1994 (ADFG). Northern flying squirrel. Alaska Department of Fish and Game Notebook Series. [www.state.ak.us/adfg/notebook/furbear/nfsquirl.htm].
Doyle, A.T. 1990. Use of riparian and upland habitats by small mammals. Journal of Mammalogy 71:14-23.
Driessen, R., G. Heit and B.R. Shute. 1998. San Bernardino flying squirrel report - Summer 1998. Population monitoring report for Bear Mountain Ski Resort Project. 9 pp.
Franklin, I.R. 1980. Evolutionary change in small populations. In M.E. Soulé and B.A. Wilcox (eds.) Conservation Biology, pp. 135-149.
Hall, D.S. 1991. Diet of the northern flying squirrel at Sagehen Creek, California. Journal of Mammalogy 72:615-617.
Hall, E.R. 1981. Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Holland, R.F. 1986. Preliminary descriptions of the terrestrial natural communities of California. Nongame Heritage Program, California Department of Fish and Game.
LaHaye. W. 2002. Personal communications with Phil Behrends of DUDEK on 4/16/02 and 5/14/02. Review of Plan Area map determined that no spotted owl pellet records exist for San Bernardino flying squirrel within the Plan Area.
Madden, J.R. 1974. Female territoriality in a Suffolk County, Long Island population of Glaucomys sabrinus. Journal of Mammalogy 55:647-652.
Maser, Z., C. Maser, and J.M. Trappe. 1985. Food habits of the northern flying squirrel in Oregon. Canadian Journal of Zoology 63:1084-1085.
McKeever, S. 1960. Food of the northern flying squirrel in northeastern California. Journal of Mammalogy 41:270-271.
Muul, I. 1969. Mating behavior, gestation period, and development of Glaucomys sabrinus. Journal of Mammalogy 50:121.
Ransome, D.B. and T.P. Sullivan. 1997. Food limitation and habitat preference of Glaucomys sabrinus and Tamiasciurus hudsonicus. Journal of Mammalogy 78:538-549.
San Jacinto Mountains Digital Library. 2000. [www.jamesreserve.edu.catabases.html/].
USFS. 1995. Biological evaluation for Bear Mountain Ski Resort's 1989 Development Plan - San Bernardino flying squirrel. 32 pp.
USFWS. 1991. Carolina northern flying squirrel Glaucomys sabrinus coloratus. Endangered and threatened species of the southeastern United States (The Red Book), FWS Region 4.
Waters, J.R. and C.J. Zabel. 1995. Northern flying squirrel densities in fir forests of northeastern California. Journal of Wildlife Management 59:858-866.
Weigl, P.D. 1978. Resource overlap, interspecific interactions, and the distribution of the flying squirrel, Glaucomys volans and G. sabrinus. American Midland Naturalist 100:83-96.
Weigl, P.D., T.W. Knowles, and A.C. Boynton. 1999. The distribution and ecology of the northern flying squirrel (Glaucomys sabrinus coloratus) in the southern Appalachians. North Carolina Wildlife Commission, Nongame and Endangered Wildlife Program, Division of Wildlife Management, Raleigh, NC. 93 pp.
Wells-Gosling, N. and L.R. Heaney. 1984. Glaucomys sabrinus. In: Mammalian Species No. 229:1-8. Published by the American Society of Mammalogists.
Witt, J.W. 1992. Home range and density estimates for the northern flying squirrel, Glaucomys sabrinus, in western Oregon. Journal of Mammalogy 73:921-929.
San Bernardino kangaroo rat (Dipodomys merriami parvus)
State: Species of Special Concern
Federal: Endangered
The San Bernardino kangaroo rat has a narrow distribution within the Plan Area, being primarily restricted to 1) the San Jacinto River from about Highway 79 (Lamb Canyon Road/Sanderson Avenue) in the north to the boundary with Forest Service land to the east, and 2) Bautista Creek from about Bautista Dam to the north and the Hixon Flat trailhead to the south. The precise status of smaller remnant populations in Reche Canyon and the northern portion of the Jurupa Mountains in the Bloomington area is unknown, but the persistence of remaining occurrences in these areas is likely tenuous given the rate of ongoing habitat destruction and fragmentation. The San Bernardino kangaroo rat typically is found in Riversidean alluvial fan sage scrub, but may occur at lower densities in Riversidean upland sage scrub, chaparral and grassland in uplands and tributaries in proximity to Riversidean alluvial fan sage scrub habitats. Conservation of Riversidean alluvial fan and upland sage scrub in the San Jacinto River and Bautista Creek is essential for conservation of this species in the Plan Area. Monitoring and adaptive management to maintain and enhance habitat in these areas also will be important for this species because of the small amount of remaining habitat. The San Bernardino kangaroo rat is a Group 3 species because of its narrow distribution in the Plan Area and the need for population monitoring and adaptive management.
The San Bernardino kangaroo rat is on the Additional Survey Needs and Procedures (Section 6.3.2) list and surveys for the species will be conducted as part of the project review process for public and private projects within the mammal species survey area where suitable habitat is present (see Mammal Species Survey Area Map, Figure 6-5 of the MSHCP, Volume I). San Bernardino kangaroo rat localities found as a result of survey efforts shall be conserved in accordance with the procedures described within Section 6.3.2, MSHCP, Volume I.
The species-specific conservation objectives developed for this species are based upon the best available scientific information existing at the time of MSHCP preparation. Pursuant to the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives may be adjusted as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 4,440 acres of occupied or suitable habitat within the historic flood plains of the San Jacinto River and Bautista Creek and their tributaries.
Surveys for San Bernardino kangaroo rat will be conducted as part of the project review process for public and private projects within the mammal species survey area where suitable habitat is present (see Mammal Species Survey Area Map, Figure 6-5 of the MSHCP, Volume I). San Bernardino kangaroo rats located as a result of survey efforts shall be conserved in accordance with the procedures described within Section 6.3.2 of the MSHCP, Volume 1.
Within the 4,440 acres of suitable habitat in the MSHCP Conservation Area, ensure that at least 75 percent of the total (3,330 acres) is occupied and that at least 20 percent of the occupied habitat (approximately 666 acres) supports a medium or higher population density (≥5 to 15 individuals per hectare; McKernan 1997) of the species as measured across any 8-year period (i.e., the approximate length of the weather cycle).
Within the MSHCP Conservation Area, Reserve Managers shall maintain or, if feasible, restore ecological processes within the historic flood plains of the San Jacinto River and Bautista Creek, their tributaries, and other locations within the Criteria Area where the San Bernardino kangaroo rat is detected in the future, given existing constraints and activities covered under the Plan. Maintenance and/or restoration of ecological processes may include: 1) allowing for natural dynamic fluvial processes of flooding, scouring and habitat regeneration, and possibly fire, to maintain healthy alluvial fan sage scrub habitat, 2) careful planning and design of existing and future authorized uses that may affect natural processes such as flood control, water conservation, and sand and gravel mining, 3) control of other uses and disturbances such as farming and discing for weed abatement, heavy grazing, off-road vehicles, and vandalism, and 4) control of invasive exotic species.
The main populations of the San Bernardino kangaroo rat in the Plan Area are in the San Jacinto River and Bautista Creek. The known occupied habitat in the San Jacinto River in this area ranges from about the San Bernardino National Forest boundary to the east to about State Highway 79 (Lamb Canyon Road/Sanderson Avenue) to the west, and is estimated to be at least 1,350 acres (USFWS 1998). However, a considerable amount of suitable habitat in this area has not been surveyed for this species. A total of approximately 3,750 acres is within proposed Core 5 along the San Jacinto River within this reach, including disturbed mined areas that account for about 230 acres and agriculture than accounts for about 312 acres. The area occupied by the San Bernardino kangaroo rat in Bautista Creek is more limited, and probably occurs in the wash above Bautista Dam about two miles southwest of the intersection of Fairview Avenue and Stetson Avenue in the north to about Hixon Flat trailhead and Bautista Springs in the south (Behrends, pers. obs.). A rough estimate of the area in Bautista Creek (in proposed Core 4) that may provide habitat for the San Bernardino kangaroo rat is approximately 690 acres, including about 155 acres of agriculture. Some of this suitable habitat that has not been surveyed for the species occurs in the tributaries to Bautista Creek and on the adjacent upland terraces. The precise limits of occupied habitat are unknown. Taken together, the total area within proposed Cores 4 and 5 is approximately 4,440 acres. This estimate is essentially the same as the USFWS estimate of approximately 4,857 acres of suitable habitat exist within Plan Area within the historic flood plains of the San Jacinto River and Bautista Creek, and their tributaries.
For the purpose of the conservation analysis, suitable habitat for the San Bernardino kangaroo rat includes Riversidean alluvial fan sage scrub, Riversidean sage scrub, chaparral and grassland within and adjacent to the San Jacinto River from Sanderson Avenue (State Highway 79) and about the boundary with Forest Service lands, Bautista Creek from south of the dam to the Hixon Flat trailhead, Laborde Canyon, Reche Canyon, San Timoteo Creek, the Santa Ana River northeast of State Highway 60, and an area at the base of the Jurupa Mountains. Currently occupied habitat within these suitable habitat areas is only known from the San Jacinto River and Bautista Creek. The other suitable habitat areas listed above are within the Criteria Area Mammal Survey Areas described in Section 6.3.2 of the MSHCP, Volume 1. For this analysis, areas mapped as disturbed/developed and agriculture are not included.
Based on the assumptions about suitable habitat, the Plan Area supports about 5,500 acres of suitable habitat for the San Bernardino kangaroo rat. Table 1 shows the conservation of suitable habitat for the San Bernardino kangaroo rat. Overall, approximately 3,748 acres (68 percent) of suitable habitat would be in the MSHCP Conservation Area. In the San Jacinto River and Bautista Creek, conservation of occupied or suitable habitat for the San Bernardino kangaroo rat in the Plan Area would be close to 100 percent (these two areas total over 4,440 acres, of which about 830 acres are disturbed/developed and agriculture).
TABLE 1
SUMMARY OF HABITAT CONSERVATION
SAN BERNARDINO KANGAROO RAT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 1,117 | 573 | 97 | 670 | 299 | 148 | 447 |
| Rivesidean Sage Scrub | 1,024 | 416 | 91 | 507 | 294 | 223 | 517 |
| Riversidean Alluvial Fan Sage Scrub | 1,843 | 819 | 877 | 1,696 | 0 | 147 | 147 |
| Grassland | 1,549 | 764 | 111 | 875 | 244 | 430 | 674 |
| TOTAL | 5,533 | 2,572 46% |
1,176 21% |
3,748 68% |
837 15% |
948 17% |
1,785 32% |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described above, the San Bernardino kangaroo rat primarily occurs in two key populations in the MSHCP Plan Area: the San Jacinto River and Bautista Creek. Historically these populations were naturally linked because Bautista Creek is a tributary to the San Jacinto River. At present these populations are isolated by an approximately 3.8-mile long concrete-lined flood control channel that runs through citrus groves and residential development. Thus these populations are effectively isolated. The main Plan Area configuration issue is to preserve the existing habitat continuity within each of the areas. Within the San Jacinto River, the USFWS (1998) identified several threats that could affect habitat connectivity and integrity, including sand and gravel mining, flood control activities, agriculture, and urban development. Based on a brief visual inspection, the main threat to the Bautista Creek population appear to be encroaching agriculture into the floodplain (P. Behrends, pers. obs.). The status of the San Bernardino kangaroo rat in other areas of identified suitable habitat such as Reche Canyon, San Timoteo Creek, Laborde Canyon and the Santa Ana River is unknown. With the possible exception of populations in the Santa Ana River that could be linked with the San Bernardino County populations upstream, these areas probably are isolated from the San Jacinto River population and would have to be self-sustaining or augmented by translocations of individuals. The Plan Area must incorporate uplands adjacent to the floodplains and maintain habitat that will allow the population of San Bernardino kangaroo rat along the San Jacinto River to expand westward towards the San Jacinto Valley through protection, habitat restoration, and/or population expansion or translocations.
In summary, conservation of the San Bernardino kangaroo rat will be achieved by inclusion of approximately 3,748 acres (68 percent) of suitable Conserved Habitat in the MSHCP Conservation Area. Virtually 100 percent of the known and high potential San Bernardino kangaroo rat occupied habitat in the San Jacinto River and Bautista Creek is within the MSHCP Conservation Area.
The Incidental Take of the San Bernardino kangaroo rat is difficult to quantify for the following reasons: 1) their use of burrows for diurnal resting sites; 2) finding a dead or impaired specimen is unlikely; and 3) losses may be masked by seasonal or annual fluctuations in numbers. For these reasons, the level of Take of the San Bernardino kangaroo rat is typically estimated as the amount of permanent and/or temporary disturbance to its habitat. Based on existing information, no known and relatively little high potential San Bernardino kangaroo rat habitat is outside the MSHCP Conservation Area. However, as shown in Table 1, approximately 1,785 acres (32 percent) of suitable habitat, as defined above, is outside the MSHCP Conservation Area. This suitable habitat, which may be subject to Incidental Take, is in areas where the status of the species is unknown. Surveys will be conducted in these areas in accordance with the procedures described within Section 6.3.2 of the MSHCP, Volume 1.
The MSHCP database includes a total of 55 records for the San Bernardino kangaroo rat. However, only 30 of the 55 records likely are valid records of the species. The 25 records that probably are not valid are from Vail Lake (1), Wilson Valley (2), and Aguanga (22). The Vail Lake and Wilson Valley records are from 1997 and 1996, respectively. The attribute data for these records indicate that these kangaroo rat were not identified to subspecies. The Aguanga records are from the 1890s, 1920s, and 1930s from the San Diego Museum of Natural History. Recent records from the Aguanga area are described as the Aguanga kangaroo rat (D. m. collinus), in accordance with the range maps for the two subspecies provided by Hall 1981, so it is likely that the Aguanga, Vail Lake and Wilson Valley records are incorrectly assigned to the San Bernardino kangaroo rat and should have been assigned to the Aguanga kangaroo rat. Most of the remaining 30 records are dated and have poor precision . General locations for these records include the San Jacinto Wildlife Area/Lake Perris, Perris, Moreno Valley, Menifee, Eden Hot Springs, Homeland, Reche Canyon, Jurupa Hills, March ARB, and Riverside areas. However, recent surveys suggest that the major extant populations of the San Bernardino kangaroo rat in Riverside County occur along the the San Jacinto River and Bautista Creek (USFWS 1998).
The vegetation descriptions in the MSHCP database for the San Bernardino kangaroo rat probably are not very reliable because the majority of the records are precision code "3" and "4." However, the habitat associations of the San Bernardino kangaroo rat generally are well understood based on recent field work by McKernan (1997; as cited in USFWS 1998; Braden and McKernan 2000) and others familiar with the subspecies.
The San Bernardino kangaroo rat, a subspecies of the Merriam's kangaroo rat (Dipodomys merriami), typically is found in Riversidean alluvial fan sage scrub and sandy loam soils, alluvial fans and flood plains, and along washes with nearby sage scrub (McKernan 1997 as cited in USFWS 1998). Braden and McKernan (2000) suggest that the San Bernardino kangaroo rat also occurs in other habitats in their range, including chaparral and even disturbed areas that are associated with alluvial processes.
Soil texture is a primary factor in this subspecies' occurrence. Sandy loam substrates allow for the digging of simple, shallow burrows (McKernan 1997 as cited by USFWS 1998). D. merriami, and other kangaroo rat species, actively avoid rocky substrates (Brown and Harney 1993). Soils along occupied portions of the San Jacinto River include riverwash, Tujunga loam sand, Soboba cobbly loamy sand, Hanford coarse sandy loam, Gorgonio loamy sand (Knecht 1971). All of these soils developed from granitic sources. However, as with vegetation types, Braden and McKernan (2000) demonstrated that the San Bernardino kangaroo rat occurs in various soil types, so soil alone cannot be used to rule out occupation. They argue that live-trapping is the only way to confirm or rule out occupation.
Portions of both habitat areas in the San Jacinto River and Bautista Creek have been surveyed or at least visually inspected from a distance by DUDEK biologist Philip Behrends, Ph.D. A reconnaissance survey conducted in June of 1999 in the San Jacinto River between about Main Street in the City of San Jacinto and the community of Valle Vista to the southeast characterized habitat occupied by the San Bernardino kangaroo rat in the MSHCP Plan Area (Behrends 1999, unpublished report). The San Jacinto River in this reach is comprised of open, unvegetated channel, and intermediate and mature Riversidean alluvial fan sage scrub, disturbed habitats, sand and gravel mining, and patches of southern willow scrub-cottonwood riparian habitat. Habitat in the open channel typically is unvegetated or very sparsely vegetated deep sand (in the northern segments) or braided channel containing large cobble and small boulders (in the southern segment). The USFWS terms such habitat as "pioneer phase" that is subject to frequent disturbance by annual floods and characterized by sparse vegetation (USFWS 1998). Open channel does not support permanent burrow systems because of its frequent disturbance and the loose consistency of the riverwash soils, but these areas are integral to the overall habitat system and life history of the San Bernardino kangaroo rat with regard to temporary use and dispersal and potential succession to more suitable habitat over time.
Much of the intermediate and mature Riversidean alluvial fan sage scrub in this reach of the San Jacinto River is disturbed and only supports trace populations (i.e., < 1 individual/ha) of the San Bernardino kangaroo rat. (This observation agrees with the conclusion by Braden and McKernan [2000] that the San Bernardino kangaroo rat may occur in mature alluvial scrub, Riversidean sage scrub and chaparral at lower densities.) While these areas support sage scrub vegetation and other plant species consistent with San Bernardino kangaroo rat occupation, including California buckwheat (Eriogonum fasciculatum), scale-broom (Lepidospartum squamatum), California croton (Croton californicus), yerba santa (Eriodictyon sp.), deerweed (Lotus scoparius), telegraph weed (Heterotheca grandiflora), western verbena (Verbena lasiostachys), and red-stemmed filaree (Erodium cicutarium), they also include a high percentage cover of invasive non-native grasses and ruderal species such as bromes (Bromus spp.), slender wild oat (Avena barbata), tocalote (Centaurea melitensis), and black mustard (Brassica nigra). These invasive species tend to preclude the San Bernardino kangaroo rat where they grow in high densities. In most cases, San Bernardino kangaroo rat scat and burrows are present but difficult to detect in disturbed habitat, indicating that the population occurs at very low or trace densities. The more southerly portions of this reach of the river near Valle Vista includes patches of relatively undisturbed alluvial fan sage scrub and easily detectable San Bernardino kangaroo rat surface sign. Such areas may support scattered patches of invasive species such as black mustard and brome grasses, but the habitat generally is open and predominantly supports native vegetation dominated by scale-broom, California buckwheat, California croton, and deerweed.
The highest quality habitat supports abundant San Bernardino kangaroo rat surface sign and is almost free of invasive species (although all areas exhibit some disturbance in the form of exotics and ground disturbances). High quality habitat supports California buckwheat, California croton, and deerweed as dominant species, and scattered Spanish bayonet (Yucca whipplei), cacti (Opuntia spp.) and a variety of native annual forbs such as phacelia (Phacelia sp.), lupine (Lupinus sp.), cryptantha (Cryptantha sp.), and popcorn flower (Plagiobothrys sp.). Such areas support little black mustard and brome grasses.
A visual inspection from several points along Bautista Canyon Road indicated that the habitat in the flood plain of Bautista Creek is similar in structure to high quality habitat in the San Jacinto River and it is expected that San Bernardino kangaroo rat densities would be similar as well.
According to Hall (1981), the species D. merriami occupies a broad range of grasslands and arid habitats in southwestern North America, extending from northwestern Nevada southward through southeastern California, Baja California and in mainland Mexico south to northern Sinaloa. It ranges eastward to southeastern Utah, western and southern Arizona, central and southern New Mexico, and into western Texas.
The historic range of the subspecies San Bernardino kangaroo rat lies west of the desert divide of the San Jacinto and San Bernardino mountains and extends from the San Bernardino Valley in San Bernardino County to the Menifee Valley in Riverside County (Lidicker 1960; Hall 1981). The USFWS estimates that at the time of listing in 1998, the San Bernardino kangaroo rat occupied approximately 6,576 ha (16, 440 acres) of suitable habitat in about seven general locations (USFWS 2000), including the Santa Ana River, Cajon Creek Wash, Lytle Creek Wash, City Creek, and upper Etiwanda Wash in San Bernardino County, and sites in western Riverside County described below.
The primary populations in the Plan Area are the San Jacinto River and Bautista Creek in the vicinity of San Jacinto, Hemet and Valle Vista. The USFWS (1998) estimated the amount of occupied and potential habitat Jacinto River at approximately 1,352 acres, but based on the more recent calculation this area probably is somewhat larger because of the broader definition of suitable habitat (USFWS 2000). The amount of occupied habitat in Bautista Creek has not been determined directly, but probably is on the order of 350-400 acres based on a rough calculation of the amount of Riversidean alluvial fan sage scrub mapped for the area in the MSHCP database. Smaller populations are historically known from Reche Canyon and the Bloomington area, but it is unclear whether these populations still exist in the MSHCP Plan Area. There also are historic records for the Homeland, Perris, March ARB, San Jacinto Wildlife/Lake Perris, and Moreno Valley areas, but it is unlikely that these populations still exist because of habitat conversion to agriculture and housing and consequent habitat fragmentation and isolation. There is also a record from the Banning Pass/Cabazon area, but the validity of this record as D. m. parvus is dubious because the subspecies D. m. simiolus occurs just to the east.
The key populations of the San Bernardino kangaroo rat are located along the San Jacinto River and Bautista Creek in the San Jacinto, Hemet and Valle Vista areas.
There are few specific studies of the subspecies San Bernardino kangaroo rat, but there is a substantial literature for the species D. merriami. The information presented in this section largely is for the species, with specific reference to the San Bernardino kangaroo rat where appropriate.
Genetics: Williams et al. (1993) provides descriptions for 19 subspecies of D. merriami. Patton and Rogers (1993a, 1993b) provide reviews of what is known of the cytogenetics (e.g., chromosomal variation) and biochemical genetics (e.g., isozyme and allozyme analyses, DNA sequencing) of heteromyid rodents, the rodent family to which D. merriami belongs. Patton and Rogers generally conclude that the understanding of heteromyid genetics is still relatively poor, the data are uneven, and that few studies have applied recent technical developments (e.g., DNA fingerprinting and sequencing). As of 1993, the only biochemical technique applied to heteromyids is protein electrophoresis, a relatively crude analytic tool by today's standards. Of interest to conservation planning would be any information relating genetics to habitat fragmentation and isolation, demography, habitat tolerance, and speciation. Unfortunately, very little information in the literature is available to address these issues.
D. merriami has 52 chromosomes and there is no reported karyotypic variation in the species (Patton and Rogers 1993a). The proportion of gene loci that are polymorphic among individuals ranges from 0.06 to 0.16 and the mean proportion of loci that are heterozygotic within individuals ranges from 0.00 to 0.061. These values, as well as values for other kangaroo rat species, are relatively low compared to other mammals (Patton and Rogers 1993b). (Patton and Rogers [1993b] caution that these summary statistics probably contain large sampling error as well as other important sources of error that limit their interpretation. Also, protein electrophoresis cannot provide the fine-grain genetic analysis possible with DNA fingerprinting and other recent techniques.) Studies of electromorphic distance for D. merriami also indicate high degrees of genetic similarity. Although Lidicker (1960) remarked that the San Bernardino kangaroo rat was noticeably smaller and more differentiated compared to other D. merriami, there is no existing evidence that it is genetically distinct from other subspecies. Furthermore, there are no genetic studies of different populations of the San Bernardino kangaroo rat to address the effects of habitat fragmentation and isolation, demography, or other issues relevant to conservation planning.
The only genetic demographic study of D. merriami identified by Patton and Rogers (1993b) was a study of spatial relationships among individual genotypes in a population of D. merriami on a 10-acre study site near Kramer, California by Johnson and Selander (1971). This study concluded, in Patton and Rogers' words, "that spatial clustering of genotypes was evident at two loci, and suggested that local structure, including the possibility of inbreeding, may characterize local kangaroo rat populations." page 264. However, their findings did not include statistical corroboration of this finding and these results must be interpreted as very preliminary.
Diet and Foraging: Many studies have reported on the diet of D. merriami (see Reichman and Price 1993 for a comprehensive review), but no specific studies have been conducted on the San Bernardino kangaroo rat. Nonetheless, it is unlikely that the San Bernardino kangaroo rat exhibits meaningfully different feeding patterns compared to other subspecies of D. merriami that would be relevant for conservation planning. D. merriami are primarily granivores (seed eaters), but they ingest herbaceous material and insects when available (Bradley and Mauer 1971; Reichman and Price 1993). They collect seeds from the substrate into fur-lined cheek pouches for transport and then store them in scattered surface caches in the vicinity of their home burrows for later retrieval and consumption (Daly et al. 1992a). Unlike some larger kangaroo rat species (e.g., D. spectabilis), D. merriami do not hoard seeds to a central location (i.e., larder hoarding). Bipedal locomotion in kangaroo rats allows them to travel large distances over open ground very quickly and exploit widely scattered food sources.
Daily Activities: D. merriami, and all other kangaroo rats, are primarily nocturnal animals, but they also exhibit crepuscular behavior around dusk and dawn. They emerge from their day burrows around dusk to engage in foraging and other activities. Animals may be active any hour of the night, but the heaviest concentration of activity tends to occur in the three- to four-hour time span just after dusk. They usually return permanently to their day burrows before dawn (Behrends et al. 1986a). Factors affecting the amount and patterns of surface activity of individuals include: (1) sex and reproductive condition, with reproductive active males traveling farther than female or males with regressed testes (Behrends et al. 1996a); and (2) moonlight, with animals reducing surface activity and shifting activity toward places with relatively dense cover (Lockard and Owings 1974; Price et al. 1984). Daly et al. (1992b) found that D. merriami shifted from nocturnal activity during full moon to more crepuscular activity during dawn and dusk periods, suggesting a more complex and fine-grain compensatory behavioral response to moonlight rather than simply reducing overall surface activity to avoid moonlight.
Reproduction: The species D. merriami, and heteromyids in general, have relatively low reproductive output for rodents (see Wilson et al. 1985). In the wild, D. merriami and other kangaroo rat species typically breed one or two times per year, with the peak breeding being mid-winter through spring, although they may breed more frequently in good years (Duke 1944; Fitch 1948; Quay 1953; Pfieffer 1956; Holdenreid 1957; Reynolds 1960; Beatley 1969; Bradley and Mauer 1971, 1973; Kenagy 1973; Reichman and Van De Graaf 1973, 1975; Van De Graaff and Balda 1973; Flake 1974). Field observations of reproductive activity by D. merriami include several records of females producing successive litters at intervals of about two months, with a minimum interval of about 45-50 days (Daly et al. 1984). Breeding activities appear to vary in relation to ecological conditions, and individuals may not breed in years when conditions are poor. In good years, females are known to breed in their natal season (Daly et al. 1984). Studies indicate that nearly all adult individuals in a population are capable of breeding, but the proportion of individuals active at non-peak breeding periods (e.g., late summer-early fall) may be smaller (e.g., Kenagy 1973). Fall and winter rains, and the consequent production of herbaceous annuals, appear to be an important factor for breeding activities, but the positive effects do not always occur in the following season; i.e., there may be lag effects in the correlation between rainfall, production of herbaceous annuals, and kangaroo rat reproduction (e.g., Beatley 1969; Chew and Butterworth 1964). Herbaceous vegetation is ingested in greater quantities during the breeding season (Bradley and Mauer 1973; Reichman and Van De Graaff 1975), and there is experimental evidence that herbaceous material or free water is necessary for successful reproduction (Soholt 1977).
A captive breeding study of D. merriami by Daly et al. (1984) found that mean litter size for 129 deliveries of captive bred females was 2.4, with few litters exceeding four pups. Interestingly, 10 litters of wild-conceived litters averaged 3.7 pups. The modal gestation period for D. merriami in this study was 33 days. D. merriami do not have a post-partum estrus (i.e., receptivity in conjunction with parturition), but they may become reproductively active within four days of removal of a nursing litter. Pups appear to stop nursing at about 25 days. The youngest mother in this captive breeding study conceived at 64 days of age and gave birth at 97 days. In the field, a female conceived her first litter between 40 and 50 days (Daly et al. 1984). D. merriami exhibit clear estrous cycles with a median length of 13.4 days and spontaneous ovulation (Wilson et al. 1985).
Based on field and laboratory studies of D. merriami, the maximal annual reproductive output of an individual female, based on a typical litter of two or three pups, is unlikely to exceed ten (Wilson et al. 1985), which is far below many other rodents that exhibit induced ovulation or post-partum estrous (e.g., murids).
Survival: Individual D. merriami have observed life spans of at least five years in the wild and at least seven years in captivity (Behrends, pers. obs.; Daly et al. 1990). However, the data on expected life span and annual survivorship of D. merriami in the field are equivocal because of the many practical limitations in measuring and interpreting survivorship (e.g., distinguishing between mortality and emigration). Nonetheless, French et al. (1967) estimated a life expectancy for D. merriami of 4.3 months in the Mojave Desert. Chew and Butterworth (1964) observed 12-19 percent annual survivorship in a trapping study in the Mojave Desert, with most disappearances occurring from October to April and attributable to juvenile disappearances and the harsh winter. Zeng and Brown (1987), on the other hand, concluded that adult survivorship appears to be relatively high and year-to-year survivorship of males and females appears to be very similar. Because D. merriami are long-lived and recruitment of juveniles into populations probably varies from year-to-year, most populations are comprised primarily of adults. After correcting for emigration, annual adult survivorship may be on the order of 75 percent (Brown and Harney 1993).
In a long-term study of predation of a D. merriami population in Palm Desert, California, Daly et al. (1990) recorded a total of 50 known or presumed predations and found that more mobile individuals were at higher risk of predation; general survivorship was not estimated because of the lack of control for emigration. Important predators in the Daly study were coyotes, snakes, owls, and shrikes. Bobcats and foxes also would be expected to be important predators of the San Bernardino kangaroo rat in western Riverside County.
Dispersal: Jones (1989) determined that D. merriami is philopatric; i.e., individuals tend to establish home ranges in proximity to their natal range. Dispersal in D. merriami is slightly male-biased, but more than 85 percent of individuals disperse less than 125 meters over their lifetimes (Jones 1989). Although recruitment of juveniles into the population is unknown, it probably varies in relation to breeding activities and ecological conditions (i.e., carrying capacity of the habitat). The data collected by French et al. (1967) and Chew and Butterworth (1964) suggests that juveniles are at high risk of disappearance, either through dispersal or mortality.
Socio-Spatial Behavior: Radio-telemetry studies and live-trapping studies of D. merriami have elucidated the basic patterns of this species' social and spatial behavior (e.g., Behrends et al. 1986a,b; Jones 1989). A review of heteromyid behavioral adaptations by Randall (1993) summarizes the fundamental aspects of D. merriami social organization. Although day burrows tend to be dispersed, this species exhibits overlapping home ranges. However, female-female overlap is less than male-male and male-female range overlap. Individuals primarily are solitary and asocial, although aggressive and non-aggressive interactions are not rare and individuals tend to tolerate familiar neighbors more than strangers. Core areas around day burrows may be aggressively defended. Although home ranges shift spatially over time, individuals tend to have long-term associations with the same individuals. Average home ranges of males and females are similar in size, and range from 0.16 ha (0.4 acre) in Arizona to 2.6 ha (6.4 acres) in Texas, with individual home ranges varying substantially (Behrends et al. 1986b).
That kangaroo rats are relatively long-lived (> 7 years in captivity), exhibit conservative reproductive traits, juvenile mortality exceeds adult mortality (French et al. 1967; Zeng and Brown 1987) and individuals disperse little between birth and adulthood (Jones 1989) all suggest that D. merriami has long-term stability in social communities.
Population densities of D. merriami can vary dramatically, probably in association with resource availability, but tempered by the conservative life history traits of the species; i.e., relatively low fecundity and recruitment of juveniles, storage of seeds, and effective predator avoidance. Geographically, typical population densities are variable and range from lows of 1 individual/ha in Texas to about 18 individuals/ha in Arizona (Behrends 1986b; Brown and Harney 1993). Typical densities in the Palm Desert area of California were approximately 6 individuals/ha over a five-year period (Behrends, pers. obs.). Subsequent trapping studies demonstrated an enormous range in abundance; fewer than 10 individuals were trapped on a 1-ha grid in drought years and more than 80 individuals in years following substantial rainfall and high production of food resources (Behrends, pers. obs.) (note that these are not density estimates for a unit area because the 1-hectare grid draws animals from beyond the grid). Reynolds (1958) conducted a 12-year trapping study in southern Arizona and recorded densities of 3.4 individuals/ha to a high of 17.3 individuals/ha. Zeng and Brown (1987) recorded population densities ranging between about 2 and 18 individuals/ha in the Chihuahuan Desert in southeastern Arizona.
Community Relationships: The community ecology of heteromyid rodents, including kangaroo rats (Dipodomys spp.), pocket mice (Perognathus and Chaetodipus spp.) and kangaroo mice (Microdipodops spp.) is among the most studied aspect of this family's biology. Brown and Harney (1993) provide a comprehensive overview and attempted synthesis of this complex subject. Presented here are some generalizations that fall from this large body of literature.
Arid grassland and desert environments support a surprising diversity of coexisting rodent granivores. The diversity and number of coexisting species vary depending on local conditions and the requirements of the constituent species. For example, the San Bernardino kangaroo rat potentially overlaps with two other kangaroo rats (D. stephensi and D. simulans), at least two pocket mice (Chaetodipus fallax and Perognathus longimembris), and at least four murids (Peromyscus maniculatus, P. eremicus, Neotoma lepida, and Reithrodontomys megalotis) that would compete for space and food resources. Brown and Harney (1993) conclude that "the composition of these assemblages is not random. Instead it is determined by interactions of the species with the physical environment, with other kinds of organisms, and with other rodent species." page 646. Generally, species that do coexist tend to occupy and exploit different microhabitats or niches or differ in their seasonality of resource exploitation. For example, a trapping program conducted along Wilson Creek east of Sage in Riverside County, California recorded three species of kangaroo rats: D. merriami collinus, D. stephensi and D. simulans. D. merriami was trapped in coarse, sandy soils adjacent to the creek, D. stephensi was trapped in sparse grassland and a dirt road away from the creek, and D. simulans was trapped in coastal sage scrub on the slopes above the creek (DUDEK 1995).
D. merriami exhibits somewhat greater habitat tolerance than other heteromyids. A survey of community assemblages by Brown and Harney (1993) found that D. merriami has one of the broadest geographic ranges and tends to be one of the most abundant species of assemblage where found.
Interspecific competition is an important component of the organization of heteromyid community structure. For example, competitive exclusion can result in nonrandom assemblages that partition the resources and habitats in the community. Other potential mechanisms of resource partitioning listed by Brown and Harney (1993) include habitat selection or restriction, independent adaptations, food partitioning and variable foraging efficiency, seed distribution, resource variability, predator-mediated coexistence, aggressive interference, and seasonality.
Kangaroo rats and other heteromyid rodents also modify their environments (Brown and Harney 1993). They dig burrows, which moves the soils and provides habitat and refugia for other species, including other rodents, reptiles, amphibians, birds and invertebrates. Collection, storage and consumption of seeds by kangaroo rats have profound effects on the vegetation structure of the habitats they occupy. For example, experiments by Brown and his colleagues in southeastern Arizona have demonstrated that kangaroo rats are a "keystone guild" where their removal from plots resulted in the habitat converting from desert shrub to grassland (Brown and Heske 1990). In addition, resource use by kangaroo rats substantially overlaps with that of seed-eating birds and harvester ants. Where kangaroo rats have been excluded in experimental plots, ants have increased dramatically (Brown and Harney 1993).
The coevolutionary results of such inter- and intraspecific community relationships and their relationship to plant communities are not understood, but it can be concluded that rodents are an important component of arid ecosystems. In addition to their direct impacts on plant communities, they are important prey for a variety of predators and their presence also affects populations of other prey such as small reptiles, lagomorphs and some birds (Brown and Harney 1993).
Physiological Ecology: Kangaroo rats and most other heteromyid species live in arid environments characterized by hot summers, long, cold winters, unpredictable precipitation, and ephemeral primary productivity of food sources (French 1993). For example, D. merriami has been observed on the surface at temperatures of -19 degrees Celsius (Kenagy 1993). Living in such extreme environmental conditions has high metabolic and thermoregulatory costs.
Kangaroo rats are perhaps most famous for their water conservation capabilities. Schmidt-Nielsen (1964) and French (1993) summarized the behavioral and physiological means by which kangaroo rats, and D. merriami, in particular, conserve water: they occupy burrows during daylight hours to avoid high temperatures; their evaporative water loss is much lower than other mammals when corrected for body mass; they have relatively low metabolic rates (about 30 percent lower than average mammals); they produce low volumes of highly concentrated urine and low-moisture feces; and their water requirements can be satisfied by oxidative or metabolic water in conjunction with the seeds and herbaceous material they consume. D. merriami also produces highly concentrated milk, thus minimizing lactational water loss.
Energy conservation is very important for species living in extreme environments. D. merriami is active on the surface the entire year (e.g., Behrends et al. 1986b, Kenagy 1973). Other than at times of starvation, there is no evidence that D. merriami goes into torpor (a kind of hibernation) to conserve resources, as do pocket mice (Perognathus and Chaetodipus) and kangaroo mice (Microdipodops) (French 1993). However, D. merriami does tend to rest at temperatures at the lower end of thermal neutrality whenever possible to conserve energy (French 1993).
These physiological and behavioral characteristics allow kangaroo rats to inhabit a broad range of arid habitats in western North America, as well as allow individuals to survive during long periods of adverse climatic conditions.
Habitat Loss: Identified threats to the San Bernardino kangaroo rat include the loss of habitat, habitat fragmentation, urban and industrial development, highway construction, flood control and water conservation projects, sand and gravel mining, grazing, and vandalism (USFWS 1998). Additional threats to the species likely include farming and discing of habitat for weed abatement, heavy grazing, and off-road vehicles. Although this species is associated with sandy washes and drainages, permanent habitat supporting sparse alluvial fan sage scrub and other occupied habitat (e.g., Riversidean sage scrub, chaparral, grasslands and disturbed habitat) often may not be in areas under the jurisdiction of the U.S. Army Corps of Engineers (i.e., within the ordinary high water mark of the drainage) or California Department of Fish and Game (i.e., streams with bed and bank). For example, non-jurisdictional benches above creek channels probably are important for this species.
Genetic Isolation: Although there appears to be little genetic variation in kangaroo rats in general (Patton and Rogers 1993a,b), a study by Johnson and Selander (1971) suggested some degree of local genetic structure and the possibility inbreeding in a population D. merriami in Kramer, California. With such small and currently isolated populations of the San Bernardino kangaroo rat, such effects could have important conservation implications. Genetic studies of the San Bernardino are urgently needed.
Disease: The relationship of parasites and associates (e.g., viruses, bacteria, spirochetes, fungi, protozoa, etc.) in disease in D. merriami is not well understood, but various studies summarized by Whitaker et al. (1993) indicate that the species supports and/or may be affected by a variety of organisms. While many of these "parasites" may be benign, others may cause disease and mortality that could have severe impacts on small, insular populations. Because of the enormous number of parasites and associates D. merriami, on a brief summary of the general types and number of genera and species are reported here. The reader is directed to Whitaker et al. (1993) for a more detailed description.
D. merriami is known to carry at least two fungi species, eight species of protozoa, four species of tapeworm (cestodes), 10 species of roundworm (nematodes), 10 species of mites, 34 species of chiggers, two species hard ticks, two species of sucking lice, one moth, and 22 species of fleas. The effects of these parasites and their associates on the health of D. merriami generally are unknown. Many may be benign, but some may be pathogenic and have deleterious effects on populations (Whitaker et al. 1993). Such effects in small, isolated populations would be particularly serious. The relationships between host and parasites, such whether they cause harm to the host, the geographic range of the parasites, and whether the number of parasites an individual carries is related to health, are all topics that require further study (Whitaker et al.1993).
Maintenance of suitable habitat will be important for this species. San Bernardino kangaroo rats that occupy the San Jacinto River and Bautista Creek, experience fluctuations in habitat quality based on the fluvial processes related to flooding and drought. Intermediate alluvial fan sage scrub, which occurs on terraces between pioneer and mature habitats, probably provides the best habitat for the species because it does not flood often, but also is fairly open (7-22 percent cover) with a low shrub canopy. The density of vegetation is particularly important for kangaroo rats as it affects their burrowing, locomotion and foraging ability. The experimental removal of vegetation can result in an increase in kangaroo rats using the more open habitat (Rosenzweig 1973; Price 1978). Pioneer and mature sage scrub stages, on the other hand, are less suitable; pioneer areas are subject to frequent flooding and mature alluvial scrub may become too dense in cover for this species. Consequently, natural fluvial processes, whereby cycles of flooding and dry periods result in dynamic fluctuations of habitat, probably are crucial for this species.
Beatley, J.C. 1969. Dependence of desert rodents on winter annuals and precipitation. Ecology 50:721-724.
Behrends, P., M. Daly, and M.I. Wilson. 1986a. Aboveground activity of Merriam's kangaroo rats (Dipodomys merriami) in relation to sex and reproduction. Behaviour 96:210-226.
Behrends, P., M. Daly, and M.I Wilson. 1986b. Range use and spatial relationships of Merriam's kangaroo rats (Dipodomys merriami). Behaviour 96:187-209.
Braden, G.T. and R.L. McKernan. 2000. A databased survey protocol and quantitative description of suitable habitat for the endangered San Bernardino kangaroo rat (Dipodomys merriami parvus). Final Report. Biology Section, San Bernardino County Museum, 35 pp.
Bradley, W.G. and R.A. Mauer. 1973. Rodents of a creosote bush community in southern Nevada. The Southwestern Naturalist 17:333-344.
Bradley, W.G. and R.A. Mauer. 1971. Reproduction and food habits of Merriam's kangaroo rat (Dipodomys merriami). Journal of Mammalogy 52:479-507.
Brown, J.H. and B.A. Harney. 1993. Population and community ecology of heteromyid rodents in temperate habitats. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No, 10 of the American Society of Mammalogists, pages 618-651.
Brown, J.H. and E.J. Heske. 1990. Mediation of a desert-grassland transition by a keystone rodent guild. Science 250:1705-1707.
Chew, R.M. and B.B. Butterworth. 1964. Ecology of rodents in Indian Cove (Mojave Desert), Joshua Tree National Monument, California. Journal of Mammalogy 45:203-225.
Daly, M., L.F. Jacobs, M.I. Wilson, and P.R. Behrends. 1992a. Scatter-hoarding by kangaroo rats Dipodomys merriami) and pilferage from their caches. Behavioral Ecology 3:102-111.
Daly, M., P. R. Behrends, M.I. Wilson, and L.F. Jacobs. 1992b. Behavioral modulation of predation risk: moonlight avoidance and crepuscular compensation in a nocturnal desert rodent, Dipodomys merriami. Animal Behaviour 44:1-9.
Daly, M., M. Wilson, P.R. Behrends, and L.F. Jacobs. 1990. Characteristics of kangaroo rats, Dipodomys merriami, associated with differential predation risk. Animal Behavior 40:380-389.
Daly, M., M.I. Wilson, and P. Behrends. 1984. Breeding of captive kangaroo rats, Dipodomys merriami and D. microps. Journal of Mammalogy 65:338-341.
Dudek and Associates, Inc. (DUDEK). 1995. Stephens' kangaroo rat assessment for the Stardust Ranch/Mission Foundation Property.
Duke, K.L. 1944. The breeding season in two species of Dipodomys. Journal of Mammalogy 25:155-160.
Fitch, H.J. 1948. Habits and economic relationships of the Tulare kangaroo rat. Journal of Mammalogy 29:5-35.
Flake, L.D. 1974. Reproduction of four rodent species in a short grass prairie of Colorado. Journal of Mammalogy 55:213-216.
French, A.R. 1993. Physiological ecology of the Heteromyidae: economics of energy and energy and water utilization. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No, 10 of the American Society of Mammalogists, pages 509-538.
French, N.R., B.G. Maza, and A.P. Aschwanden. 1967. Life spans of Dipodomys and Perognathus in the Mojave Desert. Journal of Mammalogy 48:537-548.
Hall, E.R. 1981. The Mammals of North America, Second Edition, John Wiley and Sons, New York.
Holdenreid, R. 1957. Natural history of the bannertail kangaroo rat in New Mexico. Journal of Mammalogy 38:330-350.
Johnson, W.E. and R.K. Selander. 1971. Protein variation and systematics in kangaroo rats (genus Dipodomys). Systematic Zoology 20:377-405.
Jones, W. T. 1989. Dispersal distance and the range of nightly movements in Merriam's kangaroo rats. Journal of Mammalogy 70:27-34.
Kenagy, G.J. 1973. Daily and seasonal patterns of activity and energetics in a heteromyid community. Ecology 54:1201-1219.
Knecht, A.A. 1971. Soil Survey of Western Riverside Area, California. Department of Agriculture, Washington, D.C.
Lidicker, W.Z., Jr. 1960. An analysis of intraspecific variation in the kangaroo rat Dipodomys merriami. University of California Publications in Zoology, 67:125-218.
Lockard, R.B. and D.H. Owings. 1974. Moon-related surface activity of bannertail (Dipodomys spectabilis) and Fresno (Dipodomys nitratoides) kangaroo rats. Animal Behaviour 22:262-273.
Patton, J.L. and D.S. Rogers. 1993a. Cytogenics. In H.H. Genoways and J.H. Brown (eds.) Biology of the Heteromyidae, Special Publication No, 10 of the American Society of Mammalogists, pages 236-258.
San Diego black-tailed jackrabbit (Lepus californicus bennettii)
State: Species of Special Concern
Federal: None
The San Diego black-tailed jackrabbit occurs throughout the Plan Area in open habitats, primarily including grasslands, Riversidean sage scrub, Riversidean alluvial fan sage scrub, Great Basin sagebrush, desert scrub, and juniper and oak woodlands. Although widespread in the Plan Area, the jackrabbit can be characterized as ranging from relatively uncommon to locally common. Identifying Core Areas is difficult because this species exhibits natural fluctuations in population sizes and distributions in relation to reproduction and shifting distributions and densities of food resources. With a large enough MSHCP Conservation Area however, specific management regimes will not be necessary for this species because it occurs in a variety of habitats ranging from undisturbed to highly disturbed.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 142,116 acres (44 percent) of suitable habitat in the Plan Area comprised of grassland, coastal sage scrub, Riversidean alluvial fan sage scrub, desert scrub, juniper woodland and scrub, and playas and vernal pools. Conservation in the primary core habitat areas includes Existing Core A (10,740 acres), Existing Core C (15,610 acres), Existing Core D (2,510 acres), Existing Core G (4,490 acres), Existing Core H (17,470 acres), Existing Core F (8,360 acres), Existing Core J (24,370 acres), Proposed Extension of Existing Core 2 (8,100 acres), Proposed Extension of Existing Core 6 (1,180 acres), Proposed Extension of Existing Core 7 (3,220 acres), Proposed Core 1 (7,470 acres), Proposed Core 2 (5,050 acres), Proposed Core 3 (24,920 acres), Proposed Core 4 (11,890 acres), Proposed Core 5 (3,220 acres), Proposed Core 6 (4,290 acres), Proposed Core 7 (50,000 acres), Non-contiguous Habitat Block 2 (1,230 acres), and Non-contiguous Habitat Block 5 (7,150 acres).
Include within the MSHCP Conservation Area approximately 27,700 acres of habitat linkages between Core Areas, including contiguous uplands from Estelle Mountain to Wildomar, Temescal Wash, Gavilan Hills, San Jacinto River from the National Forest to Canyon Lake, Santa Ana River, Murrieta Creek, Temecula Creek, Tucalota Creek, Wilson Creek, Tule Creek, San Timoteo Creek, and San Gorgonio Wash.
Conservation of the black-tailed jackrabbit is assessed from a landscape perspective because the species is found throughout the Plan Area. While there are definable locations for focusing conservation efforts, there does not appear to any single one or a few key populations that would be essential for conservation of the species.
For the purpose of the conservation analysis, suitable habitat for the San Diego black-tailed jackrabbit includes coastal sage scrub, desert scrub, grassland, juniper woodland and scrub, playas and vernal pools, and Riversidean alluvial fan sage scrub. Based on these assumptions about habitat, the Plan Area supports approximately 325,000 acres of suitable habitat for the black-tailed jackrabbit. Table 1 shows the conservation of suitable habitat for the San Diego black-tailed jackrabbit. Overall, approximately 142,116 acres (44 percent) of suitable habitat in the Plan Area would be in the MSHCP Conservation Area.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
SAN DIEGO BLACK-TAILED JACKRABBIT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,970 |
| Desert Scrub | 9,378 | 3,675 | 1,314 | 4,989 | 44 | 4,345 | 4,389 |
| Grassland | 146,869 | 20,011 | 22,806 | 42,817 | 12,223 | 91,829 | 104,502 |
| Juniper Woodland and Scrub | 1,082 | 336 | 274 | 609 | 23 | 450 | 473 |
| Playas and Vernal Pools | 7,914 | 3,828 | 2,923 | 6,751 | 0 | 1,163 | 1,163 |
| Riversidean Alluvial Fan Sage Scrub | 7,149 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,915 |
| TOTAL | 325,078 | 78,182 (24%) |
63,935 (20%) |
142,116 (44%) |
38,748 (12%) |
144,213 (44%) |
183,412 (56%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described below under Data Characterization, 154 of the 264 point localities have a precision of "1" or "2." Of these 154 point localities, 42 (27 percent) would be inside the MSHCP Conservation Area. Within the MSHCP Conservation Area, two points are mapped in existing agriculture and five points are in residential/urban/exotic. The relatively low percentage of point localities conserved probably reflects a lack of systematic survey information for large blocks of suitable habitat that would be conserved in the eastern portion of the Plan Area, i.e., the Vail Lake-Sage Aguanga area.
Several large blocks of habitat supporting the black-tailed jackrabbit would be conserved within the MSHCP Conservation Area, including the Santa Rosa Plateau, Lake Skinner-Diamond Valley Lake, Lake Mathews-Estelle Mountain, San Jacinto Wildlife Area-Lake Perris, Sycamore Canyon Regional Park, Lakeview Mountains, San Jacinto River, Santa Ana River, the Badlands, Vail Lake-Sage-Aguanga, Potrero Valley, Anza Valley, and the Jurupa Mountains. These large areas will conserve populations of black-tailed jackrabbit. Acreages of these Core Areas are provided in Objective 1.
The MSHCP Conservation Area also will conserve adequate habitat linkages between habitat blocks for this species. Although most dispersal distances are less than 0.25 mile, jackrabbits are capable of dispersing long distances, with one individual observed to disperse 28 miles in 17 weeks (French et al. 1965). Based on observations of jackrabbits in a variety of natural and non-natural habitats, it is expected that they will also disperse across marginal habitats such as agriculture, disturbed habitats (e.g., fallow fields, abandoned vineyards) and golf courses. They probably are not as limited in their dispersal behavior as other species with more specialized or narrow habitat requirements. The Vail Lake-Sage-Aguanga habitat block is linked to the Lake Skinner-Diamond Valley Lake habitat block via Tucalota Creek as the southern connection and via Railroad Creek-Hixon Flat to Selgato, St. Johns, and Goodhart canyons, and west to Crown Valley as the northern connection. The Vail Lake-Sage- Aguanga habitat block also is linked to the Anza Valley via Tule Creek and Culp Valley. The Badlands, San Jacinto Wildlife Area-Lake Perris, the Lakeview Mountains and the vernal pools west of Hemet are all generally contiguous with the San Jacinto River. The San Jacinto River also connects to habitat areas to the southwest such as Kabian Park, the Sedco Hills, and the linkages to Meadowbrook, the Gavilan Hills, Lake Mathews-Estelle Mountain habitat block, and Temescal Wash. Finally, the jackrabbit should remain in the Santa Ana River floodplain, with connections to populations and habitats in San Bernardino and Orange counties. Depending on future development patterns, areas that may be marginally suitable for the jackrabbit in the future include relatively isolated habitat areas such as Double Butte, Sycamore Canyon Regional Park, Box Springs Mountain Regional Park, and the Antelope Valley and French Valley areas. If the landscape surrounding these areas become heavily urbanized, the jackrabbit may be extirpated from these areas in the future.
In summary, conservation of the San Diego black-tailed jackrabbit will be achieved by inclusion of approximately 142,116 acres (44 percent) of suitable Conserved Habitat in the MSHCP Conservation Area. The MSCHP Conservation Area includes large habitat areas and adequate habitat linkages that will allow for the natural fluctuations in population densities and distribution of the jackrabbit, including the Santa Rosa Plateau, Lake Skinner-Diamond Valley Lake, Vail Lake-Sage-Wilson Valley, the Badlands-San Jacinto River, Lakeview Mountains, Sedco Hills-Kabian Park, and Anza-Cahuilla valleys.
Approximately 183,412 acres (56 percent) of suitable habitat for the jackrabbit would be outside the MSHCP Conservation Area.
The MSHCP database includes 264 records for the San Diego black-tailed jackrabbit. Of the 264 records, 122 (46 percent) are precision code "1" (an "x" and "y" coordinate that allows for good precision in the location), 32 (12 percent) are precision code "2" (one "x" or "y" coordinate or equivalent), and the remaining 110 (42 percent) are precision codes "3" or "4" (relatively imprecise locations from general areas). Most of the records are relatively recent, with 221 (84 percent) since 1990 and 43 (16 percent) pre-1990 or with no associated date. The bias toward records since 1990 is a result of the heightened awareness of the jackrabbit's potential decline in coastal southern California resulting from habitat loss and consequent inclusion as a California Species of Special Concern and former USFWS Category 2 candidate for listing as threatened or endangered.
The records are scattered throughout the Plan Area, with records only lacking from higher elevations in the San Jacinto Mountains and along the northeastern slopes of the Santa Ana Mountains. Although no particular locations in the Plan Area stand out as the "key" or "core" populations, clusters of occurrences include Wildomar-Sedco Hills-Kabian Park, Lake Skinner-Diamond Valley Lake, Wilson Valley, Tule Valley, Gavilan Hill-Lake Mathews, Sycamore Regional Park, Jurupa Hills, Sun City and Banning-Beaumont. In general, the MSHCP database for the black-tailed jackrabbit appears reasonably accurate and up to date and should be useful for conservation planning.
The black-tailed-jackrabbit occupies many diverse habitats, but primarily is found in arid regions supporting short-grass habitats. Jackrabbits typically are not found in high grass or dense brush where it is difficult for them to locomote, and the openness of open scrub habitat probably is preferred over dense chaparral. Jackrabbits are common in grasslands that are overgrazed by cattle and they are well adapted to using low-intensity agricultural habitats (Lechleitner 1959). In fact, to a point, drought and overgrazing may create better habitat for black-tailed-jackrabbits (Bronson and Tiemeir 1959). The openness of such habitat allows jackrabbits to escape predators and humans by fast, often long-distance sprints (S. Montgomery 1998). In Riverside County, black-tailed jackrabbits are found in most areas that support annual grassland, Riversidean sage scrub, alluvial fan sage scrub, Great Basin sagebrush, chaparral, disturbed habitat, and agriculture. Jackrabbits also are observed in southern willow scrub and juniper woodland (MWD and RCHCA 1995). Black-tailed-jackrabbits typically do not burrow, but take shelter at the base of shrubs in shallow depressions called forms. However, during the summer in the Mojave Desert, jackrabbits may use desert tortoise (Gopherus agassizii) burrows to escape the heat (Costa et al. 1976). Smith (1990) observed jackrabbits using burrows in the winter in northern Utah, concluding that it was an anti-predator strategy.
Black-tailed-jackrabbits locations in the MSHCP database include a broad variety of vegetation and land cover mapping types. The natural habitats with the most frequent occurrences of black-tailed jackrabbits are grassland (including alkali playa) with 64 occurrences, scrubs (including coastal sage scrub, Riversidean sage scrub, alluvial fan sage scrub, disturbed alluvial, big sagebrush scrub, and semi-desert succulent scrub) with 55 occurrences, and chaparral (including red shank chaparral) with 48 occurrences, although it is likely that observations in chaparral were in openings or along trails and roads. Other native vegetation communities with jackrabbit occurrences are oak woodland (coast live oak, Engelmann oak) with three occurrences and southern cottonwood/willow riparian with one occurrence. Many occurrences are in non-natural areas, including agriculture (dairy/livestock, field croplands, and grove/orchard) with 36 locations and residential/urban/exotic with 52 occurrences. The non-natural landscapes are difficult to assess because jackrabbits may persist in agricultural and rural residential settings, especially in the Glen Avon, Mira Loma and Pedley areas, but as these areas become more urbanized it is likely that jackrabbits will disappear. Five locations are mapped in open water/reservoir/pond, but is assumed that these records reflect lack of precision with the mapped point; all but one of the locations carries a precision code of "3."
The black-tailed jackrabbit is widespread throughout the western United States, west from central Missouri and Arkansas, and only is absent from the higher elevations of the Rocky Mountains, the Sierra Nevada, and the Cascades (Hall 1981). It ranges south into central Mexico. The subspecies L.c. bennettii, which is one of nine subspecies of black-tailed-jackrabbit (Dunn et al. 1984), is confined to coastal Southern California, with marginal records being Mt. Piños, Arroyo Seco, Pasadena, San Felipe Valley, and Jacumba (Hall 1981). The type locality for L. c. bennettii is San Diego.
The San Diego black-tailed jackrabbit is found throughout western Riverside County in suitable grassland, sage scrub and chaparral (openings) habitat. It is also found in substantial numbers in agricultural and rural residential settings. It ranges from being relatively uncommon to locally common.
A focused survey to census the jackrabbit population in western Riverside County and systematically identify key populations has not been done. Even in principle, a complete census would be difficult because of the natural population fluctuations exhibited by this species; populations may dramatically vary in size and distribution in relation to reproduction and shifting distributions and densities of food resources (French et al. 1965). Key population areas for the black-tailed jackrabbit thus are defined here as areas that currently support substantial suitable habitat for the species and frequent occurrences, especially since 1990. Some areas with fewer occurrences were included as key populations areas because of the presence of suitable habitat and/or anecdotal, but unrecorded, field observations.
Clusters of occurrences in areas that appear to be important for the conservation of this species are Lake Skinner-Diamond Valley Lake area, Sycamore Canyon Regional Park, Wildomar-Sedco Hills-Kabian Park, Sage-Wilson Valley, Tule Valley, Gavilan Hill-Lake Mathews, and Sycamore Canyon Regional Park, and Jurupa Hills. Other areas that probably are key for this species but do not have frequent occurrences in the database are Santa Rosa Plateau, the Badlands, Vail Lake-Aguanga, and Anza Valley.
Smaller, more isolated populations occur north of the Santa Ana River in the Jurupa Hills and Mira Loma-Glen Avon area, and the old vineyards and disturbed habitats in this region support a surprising number of jackrabbits (P. Behrends, pers. obs.). As the existing agricultural areas becomes more urban, jackrabbits probably will be more confined to the undeveloped hills. The database includes clusters of occurrences in the Sun City and Banning-Beaumont areas, but increasing urbanization in these areas also likely will result in a decline of jackrabbits.
Genetics: Very little data are available on black-tailed jackrabbit genetics. Best (1996) noted a diploid chromosome number of 48, but no data are available on subjects such as genetic diversity, etc. that would be helpful in conservation planning and management.
Diet and Foraging: Black-tailed jackrabbits are considered generalist herbivores (Johnson and Anderson 1984). In semidesert and desert rangelands in New Mexico, Nevada and Idaho, for example, grasses and forbs are the largest components of their diet, with shrubs less important (Johnson and Anderson 1984; Hayden 1966; Wansi et al. 1992). However, their diet shifts between season, locations, years, and vegetation types, suggesting that jackrabbits are opportunistic foragers. This is an important trait in a species that occupies a broad range of habitats and climates.
Daily Activities: Black-tailed jackrabbits primarily are nocturnal. They typically are non-burrowers and take refuge under shrubs in depressions or forms during the day. In a study of jackrabbits in the Mojave Desert, Costa et al. (1976) observed that animals became active within 30 minutes of sunset and retreated to daytime forms between dawn and sunrise. During the night they spent between 3.5 and 4.5 hours foraging, with bouts being intermittent. Non-feeding time was spent moving about and standing in open areas. Activity was reduced during the winter, but there was no detectable seasonal patterns of nocturnal activity related to season. Diurnal behavior was markedly different. During moderate temperature conditions, jackrabbits spent the entire day in their refuges. On cold winter mornings, jackrabbits basked in the sunlight, presumably helping them to keep warm and reduce energy requirements. On hot summer days, jackrabbits became restless, and moved to find shade or enter burrows dug by tortoises or by the jackrabbit itself. They retreat to burrows only during the hottest part of the day. Smith (1990) observed jackrabbits using burrows in the winter in northern Utah and concluded that it was an anti-predator strategy. Smith (1990) also found that males were more active than females in the breeding season (winter and spring).
Reproduction: Black-tailed jackrabbits exhibit a promiscuous breeding pattern, with females accepting the first interested male (Best 1996). They are induced ovulators; i.e., copulation is required to stimulate ovulation. Breeding can occur throughout the year, but shows stronger seasonality in some regions, with more northern latitudes exhibiting shorter, distinct seasons (Bronson and Tiemeir 1958; Feldhamer 1979; Wagner and Stoddart 1972). The length of the breeding season appears to be related to the production of herbaceous vegetation (Lechleitner 1959). In Butte County, California, Lechleitner (1959) observed slight seasonality, and found reproductive males and young in every month of the year. Females in his study area were pregnant every month, but showed a peak pregnancy period from January to August. In a Kansas population of black-tailed jackrabbit, Bronson and Tiemeir (1958) found that breeding occurred in January through August; a 220-day breeding season. Feldhamer (1979) recorded a breeding season from mid-February to mid-June in Idaho. The peak breeding season in northern Utah also was about January to August (Wagner and Stoddart 1972). Litter sizes vary seasonally, with larger litters later in the breeding season (Bronson and Tiemeir 1959; French et al. 1965; Lechleitner 1959). French et al. (1965) also suggested that the shorter breeding seasons in more severe northern climates are compensated for by larger litters that populations in southern latitudes with longer breeding seasons. Litters of 1-7 have been recorded (Bronson and Tiemeir 1958; Feldhamer 1979; French et al. 1965) and average litter sizes were 4.9 and 3.3 in southeastern Idaho, 2.5 in Kansas, 2.3 to 2.5 in California, and 1.8 and 2.2 in Arizona. Bronson and Tiemeir (1958) estimated that an adult female in Kansas could produce 3.8 litters per year and about 9.9 offspring, without correction for resorption of the litters (i.e., probably a slight overestimate). Lechleitner (1959) estimated productivity of about 10 young per female per year in California. Feldhamer estimated productivity of 2.5 litters per season and 10.2 young/female/ season in Idaho. The number of young produced per year is about the same throughout the range of the black-tailed jackrabbit, but populations in the north achieve similar productivity with fewer, but larger litters because of the shorter breeding season.
The gestation period of the black-tailed-jackrabbit is approximately 43 days (41-47 days) (Best 1996; Dunn et al. 1984). In response to environmental stressors (e.g., blizzards), prenatal mortality appears to be high, with 16 percent preimplantation resorption and up to 30 percent post-implantation loss (Feldhamer 1979). Young in northern California are weaned by three weeks (Lechleitner 1959). Breeding by young of the year may be uncommon (e.g., Feldhamer 1979; Lechleitner 1959). Males produce sperm at 5-7 months of age and in Butte County, California jackrabbits reach adult weight by about 32 weeks of age (Lechleitner 1959). French et al. (1965) found that population increases were followed by decreases in the breeding season and an overall decline in population productivity (i.e., a decline in fertility), while population declines were followed by increases in the breeding season and productivity. They concluded that black-tailed jackrabbit exhibit density-dependent reproduction.
Survival: Survival rates generally appear to be low and population turnover high in black-tailed jackrabbit (Feldhamer 1979; French et al. 1965; Lechleitner 1959). For example, French et al. (1965) observed that two-thirds of the cohort in southeastern Idaho turnover from the population each week during the winter due to mortality and dispersal and only 3.5 percent of the cohort remained after one year. Feldhamer (1979) noted a similar mortality rate in black-tailed jackrabbit in Idaho, with estimates of 91 percent for first-year mortality, 94 percent by two years of age, and 98 percent by three years of age. In a northern Utah population, the March-to-October mortality rate was 56 percent of the population, the October-to-March rate was 57 percent, and birth-to-October rate for juveniles was 58 percent (Wagner and Stoddart 1972). Monthly mortality rates were about 13-16 percent. Wagner and Stoddart determined that the mortality rates for juveniles and adults were about the same. They also determined that coyotes are a primary cause of mortality by noting the high correlation between coyote populations and adult mortality and documenting kills of radio-telemetered animals. Other predators of jackrabbits include bobcats (Felis rufus), American badger (Taxidea taxus), golden eagle (Aquila chrysaetos), red-tailed hawk (Buteo jamaicensis), northern harrier (Circus cyaneus), and great-horned owl (Bubo virginianus) (Wagner and Stoddart 1972). In many areas of the black-tailed-jackrabbit's range, hunting, road and landowner kills, and predation are the major cause of mortality (Bronson and Tiemeir 1959). Best (1996) concluded that jackrabbits probably do not live much longer than 7 years in the wild.
Populations are thought to fluctuate widely on 7 to 10 year cycles (Smith 1990; Wagner and Stoddart 1972).
Dispersal: Typical dispersal distances may be relatively short, but black-tailed jackrabbits are capable of dispersing long distances. French et al. (1965) recorded most dispersal distances at less than 0.25 mile, but 18 percent of juveniles dispersed greater distances and one individual dispersed 28 miles in 17 weeks. Most seasonal movements involve short distances and may be related to food availability (Bronson and Tiemeir 1959).
Socio-Spatial Behavior: Home ranges of the black-tailed jackrabbit are variable, but typically range from 20 to 140 hectares (ha) (Best 1996). French et al. (1965), however, recorded ranges of only 16 ha (40 acres) in southeastern Idaho. On the other hand, Smith (1990) used radiotelemetry to estimate home ranges in northern Utah and found ranges of less than 100 ha to 300 ha. Smith also found that home ranges typically were sexually monomorphic; ranges were only slightly larger for males compared to females. There was substantial overlap in home ranges among individuals, with no relationship to sex or age-group. Smith also found that jackrabbits tend to shift their home range over time, with the shifts occurring gradually. There also were no sex or age-group effects in home range shifts. These rather random spacing patterns are consistent with their promiscuous mating system.
The apparent density and spacing of the black-tailed jackrabbit may be related to changes in the distribution of food resources. For example, Bronson and Tiemeir (1959) found in Kansas that changes in food availability was a primary factor in population densities. Drought and overgrazing depleted food resources, resulting in aggregations of black-tailed jackrabbits in low areas where moisture collected and near crops. After rains, black-tailed jackrabbits dispersed because food was more plentiful. Population densities in this study varied from 1 rabbit/4-6 acres when food was plentiful to 1.4/acre when food was scarce. Johnson and Anderson (1984) concluded that jackrabbits in Idaho were found in higher densities in areas that had large amounts of grassland and that this distribution was related to diet rather than nesting cover. Because of shifting distributions and densities in relation to food resources, French et al. (1965) concluded that estimating population densities is difficult.
Community Relationships: Black-tailed-jackrabbits are important prey for a number of upper trophic species, including coyotes, hawks, and owls. They also are primary foragers on herbaceous material and may affect ecological systems. For example, Best (1996) noted that jackrabbits are dispersers of seeds, and in particular Opuntia seed. When food is scarce, they forage on agricultural crops and are considered a pest species. They also may be competitors with sheep and cattle during drought (Dunn et al. 1984).
Physiological Ecology: Like other species inhabiting extreme and variable habitats, it is expected that black-tailed jackrabbits have a variety of behavioral and physiological adaptations that allow them to survive extreme conditions of heat and cold and fluctuating food resources. One factor in the jackrabbit's environment is periodic reductions in food availability. Henke and Demarais (1990) food-deprived jackrabbits by 25 percent for two weeks and found several consequences, including decreased body weight, reduced kidney fat, serum bilirubin indicating liver stress, and higher cortisol concentrations and increased adrenal cortex width, both indicating a general stress response. Muscle catabolism as indicated by ketones in urine was not detectable in the two-week study.
Climatic extremes of cold and heat are a potential sources of stress for the black-tailed jackrabbit. In a study of seasonal energy requirements, Shoemaker et al. (1976) found that energy expenditure in black-tailed jackrabbits is highest in the winter in the Mojave Desert when ambient temperatures are below their zone of thermoneutrality (i.e., they are not expending extra energy for thermoregulation). In general, though, they found that energy expenditure was relatively constant throughout the year. They also found that jackrabbits utilize different amounts of energy (metabolizable calories) contained in their food in different seasons; they utilized 65 percent of the energy contained in their spring diet and only 18 percent of their winter diet. This result indicates that jackrabbits are not in energy balance during the coldest winter months because their energetic costs are higher and the energy returns from their forage are low. Finally, Shoemaker et al. found that during the hottest times of the year, jackrabbits' body temperatures rose to 410 Celsius, thus allowing them to store heat rather than dissipate it by evaporation. In addition, by attaining a body temperature consistent with the ambient temperature, jackrabbits reduce water expenditure for thermoregulation. Thus, black-tailed jackrabbits have a "voluntary" diurnal hyperthermia which helps water conservation. Costa et al. (1976) made observations of behavior that indicate relatively simple behavioral adaptations to cold winter and hot summer temperatures. During moderate temperature conditions, jackrabbits spent the entire day in their refuges and move very little. On cold winter mornings, they bask in the sunlight, presumably helping them to keep warm and reduce energy requirements. On hot summer days, jackrabbits become restless, and move to find shade or enter burrows dug by tortoises or by the jackrabbit itself. They retreat to burrows only during the hottest part of the day. Best (1996) noted that their large ears may serve conductive, convective, or radiative heat exchange, allowing them to maintain lower temperatures. Dunn et al. (1984) indicate that jackrabbits also are able to reduce water loss by excreting dry feces.
Loss of Habitat: Urban development, habitat loss, and habitat fragmentation and isolation of populations are all potential long-term risks to jackrabbits in the MSHCP Plan Area. They may disappear from a location when the size of the habitat patch declines to some critical point. Assuming that black-tailed jackrabbits exhibit drastic population fluctuations in the MSHCP study as they do elsewhere (Smith 1990; Wagner and Stoddart 1972), the risk of extirpation from marginal isolated habitat patches probably is high. Suitable habitat linkages, including agriculture, may be very important for colonization of unoccupied habitat patches.
Disease: As summarized by Best (1996) and Dunn et al. (1984), black-tailed jackrabbits are known to carry wide variety of ectoparasites, including ticks, fleas, mites, lice and flies. Endoparasites include protozoans, cestodes (tapeworms), and nematodes (roundworms). According to Dunn et al. (1984), jackrabbits also can be infected with tularemia, Q fever, equine encephalitis, brucellousus, and Rocky Mountain spotted fever.
Anthropogenic Risks: Throughout their range, and presumably in the MSHCP Plan Area as well, jackrabbits suffer substantial mortality from road kills, hunting, and landowner kills. It is possible that pet dogs (Canis lupus familiaris) from residential developments are a source of mortality, but there are no data for western Riverside County. However, Lechleitner (1958) determined that dogs were the only predator that killed substantial numbers of jackrabbits in the Sacramento area.
It is not clear what factors determine or limit the distribution and densities of black-tailed jackrabbits in the MSHCP Plan Area. Elsewhere populations and distributions vary in relation to food resources and density-dependent reproduction (e.g., Bronson and Tiemeir 1959; French et al. 1965; Johnson and Anderson 1984). The MSHCP database indicates that they occur in suitable habitat throughout the Plan Area (also S. Montgomery 1998), but there appears to be areas with particularly high densities (e.g., the Santa Rosa Plateau, Lake Skinner-Diamond Valley Lake, the Badlands, Lakeview Mountains. and the Sedco Hills and Kabian Park area). They also are common in the San Jacinto River south of Hemet (P. Behrends, pers. obs.). The ultimate conservation plan will be need to account for populations fluctuations and provide adequate habitat for the species to disperse.
Best, T.L. 1996. Lepus californicus, Mammalian Species, Publication of the American Society of Mammalogists, pp. 1-10.
Bronson, F.H. and O.W. Tiemeir. 1958. Reproduction and age distribution of black-tailed jack rabbits in Kansas. Journal of Wildlife Management 22:409-414.
Bronson, F.H. and O.W. Tiemeir. 1959. The relationship of precipitation and black-tailed jack rabbit populations in Kansas. Evolution 40:194-198.
Costa, W.R., K.A. Nagy, and V.H. Shoemaker. 1976. Observations of the behavior of jackrabbits (Lepus californicus) in the Mojave Desert. Journal of Mammalogy 57:399-402.
Dunn, J.P., J.A. Chapman, and R.E. Marsh. 1982. Jackrabbits. In J.A. Chapman and G.A. Feldhamer (eds.) Mammals of North America, pp 124-145.
Feldhamer, G.A. 1979. Age, sex ratios, and reproductive potential in black-tailed jackrabbits. Mammalia 43:473-478.
French, N.R., R. McBride, and J. Detmer. 1965. Fertility and population density of the black-tailed-jackrabbit. Journal of Wildlife Management 29:14-26.
Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York. 2 Vol. 1181 pp.
Hayden, P. 1966. Food habits of black-tailed jack rabbits in southern Nevada. Journal of Mammalogy 47:42-46.
Henke, S.E. and S. Demarais. 1990. Effect of diet on condition indices in black-tailed jackrabbits. Journal of Wildlife Disease 26:28-33.
Johnson, R.D. and J.E. Anderson. 1984. Diets of black-tailed jackrabbits in relation to population density and vegetation. Journal of Wildlife Management 37:46-47.
Lechleitner, R.R. 1959. Sex ratio, age classes and reproduction of the black-tailed jackrabbit. Journal of Mammalogy 40:63-81.
Lechleitner, R.R. 1958. Movements, density, and mortality in a black-tailed jackrabbit population. Journal of Wildlife Management 22:371-384.
Metropolitan Water District (MWD) and Riverside County Habitat Conservation Agency (RCHCA). 1995. Lake Mathews Multiple Species Habitat Conservation Plan and Natural Community Conservation Plan: Vol. 2.
Shoemaker, V.H., K.A. Nagy, and W.R. Costa. 1976. Energy utilization and temperature regulation by jackrabbits (Lepus californicus) in the Mojave Desert. Physiological Zoology 49:364-375.
Smith, G.W. 1990. Home range and activity patterns of black-tailed jackrabbits. Great Basin Naturalist 50:249-256.
Wagner, F.H. and L.C. Stoddart. 1972. Influence of coyote predation on black-tailed jackrabbit populations in Utah. Journal of Wildlife Management 36:329-342.
Wansi, T., R.D. Pieper, R.F. Beck, and L.W. Murray. 1992. Botanical content of black-tailed-jackrabbit diets on semidesert rangeland. Great Basin Naturalist 52:300-308.
San Diego desert woodrat (Neotoma lepida intermedia)
State: Species of Special Concern
Federal: None
The San Diego desert woodrat is found throughout the Plan Area in sage scrub and chaparral wherever there are rock outcrops, boulders, cactus patches and dense undergrowth. The largest contiguous populations probably are in Lake Mathews-Estelle Mountain, Kabian area, the Badlands, San Jacinto Wildlife Area-Lake Perris, Lake Skinner-Diamond Valley Lake, Vail Lake-Sage, and on the Santa Rosa Plateau. As long as adequate microhabitats are conserved, this species will remain viable in the Plan Area. No specific management regimes are anticipated for maintaining an adequate amount of habitat for this species.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 364,828 acres (62 percent) of suitable habitat in the Plan Area comprised of chaparral, coastal sage scrub, Riversidean alluvial fan sage scrub, desert scrub, and juniper woodland and scrub. Conservation in the primary core habitat areas includes Existing Core C (15,610 acres), Existing Core G (4,490 acres), Existing Core H (17,470 acres), Existing Core F (8,360 acres), Existing Core J (24,370 acres), Proposed Extension of Existing Core 2 (8,100 acres), Proposed Extension of Existing Core 6 (1,180 acres), Proposed Extension of Existing Core 7 (3,220 acres), Proposed Core 1 (7,470 acres), Proposed Core 2 (5,050 acres), Proposed Core 3 (24,920 acres), Proposed Core 4 (11,890 acres), Proposed Core 5 (3,220 acres), Proposed Core 6 (4,290 acres), Proposed Core 7 (50,000 acres), and Non-contiguous Habitat Block 5 (7,150 acres).
For the purpose of the conservation analysis, suitable habitat for the San Diego desert woodrat includes chaparral, coastal sage scrub (including Riversidean and Diegan coastal sage scrub), desert scrub, juniper woodland and scrub, and Riversidean alluvial fan sage scrub. Based on these assumptions about habitat, the Plan Area supports approximately 583,780 acres of suitable habitat for the San Diego desert woodrat. Table 1 shows the conservation of suitable habitat for the San Diego desert woodrat. Overall, approximately 364,830 acres (62 percent) of suitable habitat in the Plan Area would be in the MSHCP Conservation Area.
As described below under Data Characterization, 48 of the 123 point localities have a precision of "1" or "2." Of these 48 point localities, 24 (50 percent) would be inside the MSHCP Conservation Area.
Conservation of the San Diego desert woodrat can be considered from a landscape perspective because the species is found throughout the Plan Area. Even though desert woodrat dens are tied to specific microhabitats such as cactus patches, rock outcrops and dense shrub cover, these microhabitats are common in suitable habitat throughout the Plan Area and can be analyzed at the landscape level. Furthermore, while there are definable locations for focusing conservation efforts, there does not appear to any single one or a few key populations that would be essential for conservation of the species in the Plan Area.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
SAN DIEGO DESERT WOODRAT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Chaparral | 413,488 | 64,899 | 207,381 | 272,280 | 59,582 | 81,626 | 141,208 |
| Coastal Sage Scrub | 152,686 | 47,161 | 34,555 | 81,716 | 26,241 | 44,729 | 70,970 |
| Desert Scrub | 9,378 | 3,675 | 1,314 | 4,989 | 44 | 4,345 | 4,389 |
| Juniper Woodland and Scrub | 1,082 | 336 | 274 | 609 | 23 | 450 | 473 |
| Riversidean Alluvial Fan Sage Scrub | 7,149 | 3,171 | 2,063 | 5,234 | 217 | 1,697 | 1,915 |
| TOTAL | 583,783 | 119,242 (20%) |
245,587 (42%) |
364,828 (62%) |
86,107 (15%) |
132,847 (23%) |
218,955 (38%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Very little is known about the relationship between populations of woodrats in the different parts of the Plan Area. For example, no studies have been performed to determine whether there are genetic differences in geographically distinct populations that would be important for reserve configuration, and thus whether genetic exchange between reserve areas would be important for sustaining viable populations. Woodrats are sedentary with relatively small home ranges (Bleich and Schwartz 1975), and little is known of their dispersal behavior. Given their sedentary behavior, it seems unlikely that woodrats would disperse long distances through unsuitable habitat. Consequently, it should be assumed that desert woodrats will be confined to areas with relatively contiguous habitat and be unlikely to disperse between distant isolated habitat areas. Given the existing distribution of suitable habitat and the proposed reserve design, the Plan Area probably contains four main contiguous habitat complexes for the woodrat.
Smaller habitat areas that probably would be isolated from the larger habitat complexes are the Jurupa Mountains, Box Springs Mountain, Lakeview Mountains, Sycamore Canyon Regional Park, Norco Hills, Double Butte, Motte-Rimrock Reserve, and Warm Springs Creek. Woodrats in these areas may be at relatively high risk of extirpation because a single catastrophic event such as a wildfire or even extreme predation pressure could devastate a local population to a level beyond recovery.
The Santa Ana Mountain foothills-Santa Rosa Plateau form a large, contiguous habitat area connected by Public/Quasi-Public lands, Criteria Area, and rural mountainous designation areas. This habitat complex also includes extensive contiguous habitat in north San Diego County. Much of this area is chaparral and mesic coastal sage scrub. The only significant potential barrier in this area is State Highway 74 (Ortega Highway) between Lake Elsinore and Orange County. Two other roads may be potential barriers (Clinton Keith Road-Tenaja Road and De Luz Road), but these roads are very rural with relatively low traffic levels.
Lake Mathews-Estelle Mountain generally is contiguous with the Steele Peak reserve area. State Highway 74 is a potential barrier to movement to the Kabian area and Railroad Canyon Road is a potential barrier to movement between Kabian and the Sedco Hills. Culverts under these roads would allow for movement of woodrats between these areas. There is some potential for woodrats to move between this habitat complex and the Santa Ana Mountains foothills along Indian Canyon or Horsethief Canyon, but the crossings under Interstate 15 may be too long for woodrats.
By far the largest intact habitat complex for the desert woodrat is the Badlands-San Jacinto Mountain foothills-Agua Tibia Wilderness complex. This area comprises approximately the eastern one-third of the Plan Area. With the exception of several major highways, continuous habitat for the woodrat runs from the northwest extent of the Badlands north of Moreno Valley south to the foothills of the San Jacinto Mountains in the area of Sage and farther south to the Agua Tibia Wilderness and the Cahuilla and Anza valleys. The southern part of this habitat complex also is contiguous with habitat in San Diego County. This complex includes the San Jacinto Wildlife Area-Lake Perris and Lake Skinner-Diamond Valley Lake core reserves.
Major roads that interrupt this large habitat area include the following: