Field Guide to Mammals
of Southern California
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Los Angeles Pocket Mouse (Perognathus longimembris brevinasus)
In California, the known range of the Los Angeles pocket mouse extends from the cities of Burbank and San Fernando on the northwest to San Bernardino on the northeast and to the vicinity of Cabazon, Hemet, and Aguanga on the east and southeast. The subspecies' geographic limits to the southwest are unclear, but they probably lie somewhere near the Hollywood Hills (Williams 1986). Bond (1977) identified specimens from Ranchita and Warner Pass in San Diego County as P. l. brevinasus , but Williams (1986) believed these were probably P. l. internationalis. California Natural Diversity Database records indicate that this subspecies was historically found in several inland valleys of western Riverside and San Bernardino Counties (California Natural Diversity Database 2002). Williams (1986) noted that more information is needed on the extant distribution of this species.The geographic range described above is almost entirely outside National Forest System lands. One historic occurrence of Los Angeles pocket mouse listed by Williams (1986) is at Dos Palmas Spring at the base of the Santa Rosa Mountains, well to the east of the described range and within the San Jacinto District of the San Bernardino National Forest. Historic localities near Cabazon, Banning, Valle Vista, and Cajon Wash are close to National Forest System lands, although the transition to steep, low-quality habitat occurs rapidly in these areas (Stephenson and Calcarone 1999). Additional potential habitat occurs near Lytle Creek and the San Jacinto River on or adjacent to National Forest System lands (Loe pers. comm.).
According to Williams (1986), the species P. longimembris is in need of taxonomic revision. There are 11 species of pocket mice in this genus, some of which may be very difficult to identify (Ingles 1965). Some of the specimens currently assigned to the subspecies P. l. brevinasus, particularly those found at Ranchita and Whitewater Ranch may be more appropriately assigned to other taxa.
The Los Angeles pocket mouse occupies areas with fine, sandy soils, typically in arid grassland or coastal sage scrub habitats (Genoways and Brown 1993). The upper elevation limit of records listed in Williams (1986) is 3,500 feet (1,065 meters) (at Dos Palmas Spring), but most documented occurrences (all but two) are below 2,200 feet (670 meters). Pocket mice require soils that allow them to construct burrows 2-3 feet deep for escape from the desert heat and predators. These burrows generally include individual chambers that serve as nest cavities and food storage locations.
Perognathus young are born in burrow nests, usually in late spring through early fall. Litter size ranges from one to eight, and one female may have multiple litters throughout the year (Whitaker 1991). Several studies suggest that reproduction in heteromyids may be dependent on availability of annual vegetation.
All members of the Heteromyidae family are nocturnal (Burt 1980). P. longimembris is a seasonally active pocket mouse; it is generally inactive from October to January (Whitaker 1991).
Diet and Foraging
P. longimembris feed on seeds and greens, which are stored in underground chambers (Whitaker 1991).
No information is available for this species. Pocket mice of the P. longimembris group are nocturnal, solitary, and generally exhibit strong intraspecific aggression (Dodd 1996).
Rattlesnakes, hawks, owls, coyotes, foxes, bobcats, mountain lions, weasels, badgers, and skunks likely predate the Los Angeles pocket mouse.
Bartholomew, G.A.; Cade, T. 1957. Temperature regulation, hibernation, and aestivation in the little pocket mouse, Perognathus longimembris. Journal Mammal. 38: 60-72.
Bond, S.I. 1977. An annotated list of the mammals of San Diego County, California. Transactions of the San Diego Society of Natural History 18(14): 229–248.
Burt, W.H. 1980. A field guide to the mammals of North America North of Mexico. New York: Houghton Mifflin Company. California Natural Diversity Database. (2001, September 5 - last update). RareFind 2, Version 2.2.2, Sacramento, CA: California Department of Fish and Game. 2002.
CVMSHP/NCCP. 2003. Coachella Valley multiple species habitat conservation plan and natural communities conservation plan. Coachella Valley Association of Governments.
Dodd, S.C. 1996. Report of the 1996 Palm Springs pocket mouse (Perognathus longimembris bangsi) surveys. Palm Desert, CA. Unpublished report to the Coachella Valley Association of Governments.
Genoways, H.H.; Brown; J.H., eds. 1993. Biology of the Heteromyidae. Special publication of the American Society of Mammalogists. Provo, Utah: Brigham Young University.
Ingels, Lloyd. 1965. Mammals of the Pacific states. Stanford, CA: Stanford University Press.
Whitaker, J.O., Jr. 1991. National Audubon Society guide to North American mammals. New York: Alfred A. Knopf.
Williams, D.F. 1986. Mammalian species of concern in California. California Department of Fish and Game Report 86-91. Sacramento, CA: California Department of Fish and Game.
Winter, K. 1998. Los Angeles pocket mouse. Unpublished document. Evaluation and documentation form for the Los Angeles pocket mouse. USDA Forest Service.
Information gathered from California DFG - California Interagency Wildlife Task Group