Field Guide to Mammals
of Southern California
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Tehachapi White-Eared Pocket Mouse (Perognathus alticolus inexpectatus)
White-eared pocket mouse (Perognathus alticolus) is known to occur in arid shrub and forest communities in south-central California in Kern, Ventura, Los Angeles, and San Bernardino Counties. Tehachapi white-eared pocket mouse is endemic to the Tehachapi Mountains and western Transverse Ranges of southern Kern County (Tehachapi, Tehachapi Peak, Sand Canyon, and Oak Creek Canyon) and northern Los Angeles County (Lebec, Gorman, Lake Hughes, Quail Lake, and Elizabeth Lake), west to the Mount Pinos/Frazier Mountain region (Pinyon Pines and Cuddy Valley) on either side of the Kern/ Ventura County line (Best 1994). The range of Perognathus alticolus inexpectus is disjunct from the conspecific Perognathus alticolus alticolus. The latter subspecies is found further south in the San Bernardino Mountains. Williams (1986) speculates that this allopatric distribution may be more apparent than real. Based on museum records and historic information, known localities on National Forest System lands are near Lake Hughes, Elizabeth Lake, and Quail Lake on the desert side of the Castaic Ranges on and adjacent to the Angeles National Forest, and at Pinyon Pines and Cuddy Valley in the Mount Pinos/ Frazier Mountain region of the Los Padres National Forest (Best 1994, Williams 1986). There is a recent observation at Chuchupate Campground of individuals that may belong to this taxon; individuals were found in 1998 by public health biologists monitoring vector-borne diseases (Stephenson and Calcarone 1999). Extant populations may also occur at Sand Canyon, 13.3 miles (21.4 kilometers) east of Tehachapi in Kern County, and at Oak Creek Canyon in Joshua tree woodland near Mohave. These locations are north of the Angeles National Forest. The most recent records are of individuals trapped in 2001 from Bronco Canyon and Cameron Creek, both well north of the Angeles National Forest (Patton pers. comm.).
White-eared pocket mouse is an isolated allospecies of Great Basin pocket mouse (Perognathus parvus) (Williams 1986). Hall (1981) recognized two subspecies of white-eared pocket mouse (also known as P. alticola): San Bernardino white-eared pocket mouse (P. a. alticolus) and Tehachapi white-eared pocket mouse (P. a. inexpectatus).
Habitat associations of Tehachapi white-eared pocket mouse are not well defined. The species has been collected in arid annual grassland, desert scrub communities, Joshua and pinyon pine woodland, sagebrush/rabbitbrush scrub, a grain field, and in open desert-side pine forest at elevations of 3,500- 6,000 feet (1,070-1,830 meters) (Williams 1986). Williams (1986) identified the desert slopes of the Tehachapi and San Gabriel Mountain Ranges as areas likely to support this species. The microhabitat requirements of this subspecies are poorly known and even less is known about its diet (in captivity, white-eared pocket mice ate rolled oats, sunflower seeds, and vegetable greens). It is assumed that white-eared pocket mice eat grass seeds and perhaps some insects, and that free water is not required (Los Padres National Forest 2003).
There is no information available on the reproductive biology of the Tehachapi white-eared pocket mouse. In the congeneric Great Basin pocket mouse, breeding occurs from May to July, and one or two litters may be produced. The breeding period can extend into fall when conditions are favorable. The gestation period is 21–25 days, with the average litter size ranging from 3.9 offspring in south-central Washington to 5.6 in Nevada (USDA Forest Service 2002).
The species is nocturnal and uses underground burrows for cover and rearing of young. White-eared pocket mouse may enter torpor during high summer and low winter temperatures (Zeiner and others 1990). The CNDDB indicates that the Tehachapi white-eared pocket mouse burrows for cover and nesting, and that this subspecies avoids extreme weather by aestivating during portions of the summer and by hibernating in the winter.
Diet and Foraging
In captivity, white-eared pocket mice ate rolled oats, sunflower seeds, and vegetable greens; however, no data are available on the natural diet of this species (Best 1994). Great Basin pocket mice consume primarily grass and forb seeds, but will occasionally eat some green vegetation and insects (USDA Forest Service 2002). Foraging occurs above ground in open areas and beneath shrubs, usually at night.
No information is available. Throughout its range, the distribution and abundance of this pocket mouse is poorly known. Much of our knowledge of the Tehachapi white-eared pocket mouse is based on historical trapping records and additional studies are needed to determine its current distribution and abundance. Based on the paucity of specimens and the general inability to find the Tehachapi white-eared pocket mouse, Williams (1986) concluded that "their populations must be small, scattered, and vulnerable to changes in habitat quality." This taxon is believed to be declining due to loss of habitat (Winter 1998).
Common predators of white-eared pocket mice include owls, hawks, foxes, skunks, and snakes (Zeiner and others 1990).
Best, T.L. 1994. Perognathus alticolus. Mammalian Species 463: 1–4. Published by the American Society of Mammalogists.
Hall, E.R. 1981. The mammals of North America. 2d ed. New York: John Wiley & Sons.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment: Habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Los Padres National Forest. 2003. Tahachipi white-eared pocket mouse. Species Accounts for the Los Padres National Forest.
USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Ed.). Fire Effects Information System. [Homepage of USDA Forest Service], [Online]. Available: http://www.fs.fed.us/ database/feis/ [2002, January 21].
Williams, D.F. 1986. Mammalian species of concern in California. California Department of Fish and Game Report 86-1. Sacramento, CA: California Department of Fish and Game.
Williams, Daniel. 1993. Perognathus alticola. In: Genoways, H.; Brown, J., eds. Biology of the Heteromyidae. Special Publication No. 10, The American Society of Mammalogists.
Winter, K. 1998. Tehachapi white-eared pocket mouse. Region 5 USFS sensitive animal species evaluation and documentation form. USDA Forest Service, unpublished data.
Zeiner, D.C.;Laudenslayer, W.F., Jr.; Mayer, K.E.; White, M., eds. 1990. California's wildlife. Volume III: Mammals. Sacramento, CA: California Department of Fish and Game.
Information gathered from California DFG - California Interagency Wildlife Task Group