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 | |