Publications:

Literature Review

Palm Springs pocket mouse

Perognathus longimembris bangsi

USFWS: No status
CDFG: California Species of Special Concern

Background

Distribution, Abundance and Trends. The Palm Springs pocket mouse is one of seven subspecies of Perognathus longimembris, the "silky pocket mice" that occur in southern California. The species is the smallest of the Heteromyidae family which also includes kangaroo rats, kangaroo mice, and spiny pocket mice. The Palm Springs pocket mouse was originally described by Mearns (1898) with the type locality in Palm Springs. This subspecies occurs in the lower Sonoran life zone from the San Gorgonio Pass area east to the Little San Bernardino Mountains and south along the eastern edge of the Peninsular Range to Borrego Valley and the east side of San Felipe Narrows (Hall 1981). There is no evidence that this subspecies' range is different than what has been described in the past (Dodd 1996), although its habitat has been greatly reduced by urbanization and agriculture in the Coachella Valley.

The Palm Springs pocket mouse is known to hybridize with the Los Angeles pocket mouse (P.l. brevinasus) along its western boundary. Hybridization also occurs, although the extent is not known, with other subspecies, the Jacumba pocket mouse (P. l. internationalis) to the south, and little pocket mouse (P. l. longimembris) to the north.

Generally, their habitat is described as having level to gently sloping topography, sparse to moderate vegetative cover, and loosely packed or sandy soils. The species was found broadly distributed in the Plan area on slopes ranging from 0% to approximately 15%. The Plan area contains the major portion of the range of this species, including the western, northern, and eastern limits of the species' range. The southern boundary of the range extends out of the Plan area into Imperial, and San Diego counties. The species occurs on three existing preserves: the Coachella Valley Preserve, the Whitewater River Floodplain Preserve, and the Willow Hole-Edom Hill Preserve/ACEC. It occurs at the highest reported densities for the Plan area in the Snow Creek area. Three individuals were captured in a small mammal trapping grid (Tierra Madre Consultants 1999) in the blowsand habitat adjoining the San Gorgonio River wash just north of One Horse Spring; this location is approximately 3 miles west of Snow Creek Road. Surveys completed for this plan (Dodd 1999) confirmed that the species also occurs at Dos Palmas Preserve/ACEC and in the Cottonwood Canyon area of Joshua Tree National Park. Tests to determine that the subspecies captured in these areas is bangsi and not longimembris have not been finalized.

According to the survey results of Shana Dodd in 1995 and 1999 (Dodd 1996, 1999) the highest densities of this pocket mouse occur at the western end of the Plan area, with lower densities occurring further east. Her live trapping data, which are summarized in the table below, indicate that this species is most abundant throughout the Snow Creek to Windy Point area. She describes the Palm Springs pocket mouse as moderately abundant in the Highway 62/Mission Creek area, where the species is not currently protected. Considerable unprotected habitat also occurs adjacent to the Willow Hole Preserve; Dodd (1996) describes the density of this species at Willow Hole as moderate. Additional density estimates were made for the Palm Springs pocket mouse, based on live trapping on two 0.5 ha grids located west or Snow Creek Road, approximately ½-mile north of Snow Creek Village in the Snow Creek area (Spencer et al. 2000). The minimum density was 81.6 individuals/ha and 63.3 individuals/ha, on two adjacent grids.

Our understanding of the ecology of the Palm Springs pocket mouse arises largely from the observations of mammalogists studying other species. Pocket mice of the P. longimembris group are nocturnal, solitary, and generally exhibit strong intraspecific aggression (Dodd 1996). They spend the day in burrows they construct, comprised of a system of tunnels and resting areas, with the entrance plugged. This species generally breeds from January to August, with a peak of activity from March to May (Dodd 1996). Several studies suggest that reproduction in heteromyids may be dependent on availability of annual vegetation. The little pocket mice hibernate in winter and are active above ground in spring, summer, and fall (Bartholomew and Cade 1957).

Estimates of home range size are not available for the Palm Springs pocket mouse. In Joshua Tree National Park, home ranges of P. longimembris range from 38.7 to 84.4 meters (Chew and Butterworth 1964); in this study densities ranged from 0.85 to 1.74 individuals/ha. In Nevada, home ranges of males ranged from 12.4 to 31.6 meters and home ranges of females from 13.7 to 40.5 meters (Maza et al. 1973). O'Farrell (1978) determined that home range for both sexes varied from 0.28 ha in early spring to 0.80 ha in late fall.

TABLE 2.27 RESULTS OF LIVE TRAPPING FOR PALM SPRINGS POCKET MOUSE ¹

Threats and Limiting Factors. Threats to this species and its habitat within the Coachella Valley include agricultural development, urban development, construction of roads, railroads, airports and other structures, off-highway vehicle use, illegal trash dumping, and domestic animal predators.

Special Considerations. This species is generally associated with sandy soils. Thus, long-term viability of populations will require the continued functioning of the sand source and transport systems that sustain the habitat.