Stephens' Kangaroo Rat

Dipodomys stephensi

Description

Dipodomys stephensi (Stephens' kangaroo rat) is a small rodent with a large head, external cheek pouches, elongated and well-developed hind legs used for jumping, and small front legs used for grasping food. Body length reaches about 12 in (30 cm), and the tail is typically one and a half times the length of the body. Full grown, this kangaroo rat weighs about 2.5 oz (90 g). This species can be distinguished from near relatives by a narrower white tail band, dusky soles on the hind feet, and a more grizzled appearance.

Behavior

Stephens' kangaroo rat, like all kangaroo rats, is nocturnal. It spends the day in underground burrows and forages for seeds on the surface after dark. Young are born in spring or early summer. The size of the population can fluctuate wildly from season to season and from year to year.

Habitat

Habitats for this species are usually described as sparse, coastal sage scrub or annual grassland that has been slightly disturbed. Ideally, the scrub or grassland is part of a mosaic of other habitat types. The terrain is typically flat or gently rolling. The kangaroo rat may move into cultivated fields when they are allowed to lie fallow. Stephens' kangaroo rat is most abundant where stands of native vegetation still remain.

Distribution

Stephens' kangaroo rat is endemic to the Perris and San Jacinto valleys in western Riverside County and to the San Luis Rey and Temecula valleys in northern San Diego County, California. It has been estimated that at the turn of the century 308,750 acres (125,000 hectares) of suitable habitat were available to this species. By 1984, only about 125,000 acres (50,500 hectares) remained, mostly in isolated patches. Only about 21,000 acres (8,500 hectares) of habitat are in areas of 0.4 sq m (1 sq km) or larger. As the flat valleys have become more populated, the Stephens' kangaroo rat has been increasingly confined to the bases of hills, the tops of level ridges, and the margins of plowed fields. Suitable habitat remains at Lake Henshaw, the Fallbrook Naval Weapons Annex, and Lake Matthews. On the east side of the San Jacinto Valley, the species has been confined to the edges of plowed fields. It has been reported from the Lakeview Mountains and from the Beaumont-Banning Plain. Most of these areas are experiencing a building boom as urbanization sweeps north and west from San Diego and south from Palm Springs and Riverside. There is no current estimate of the total Stephens' kangaroo rat population, but both overall numbers and average densities have declined steeply. Loss of habitat to development continues at an accelerating rate.

Threats

The rapid rate of development in Riverside County clearly imperils the continued existence of the Stephens' kangaroo rat. Most of the Stephens' kangaroo rat habitat is privately owned and a prime target for development. The Fish and Wildlife Service (FWS) has reported that some landowners have plowed or disked their lands after being informed of the presence of the kangaroo rat; other populations have suspiciously disappeared, apparently the victims of rodenticide.

Conservation and Recovery

Only about 15% of its range is on federal lands. The Bureau of Land Management, which owns several small parcels of suitable habitat near Lake Elsinore, is pursuing land exchanges to consolidate its holdings to provide a preserve for the Stephens' kangaroo rat. In order to head off continuing conflicts between landowners, developers, conservationists, and the FWS, Riverside County is fashioning a Habitat Conservation Plan for the kangaroo rat. The plan is intended to identify sites for a viable Stephens' kangaroo rat preserve. In late 1988 the county imposed an "impact fee" to be charged developers in order to raise funds for the preserve. In 1990, the FWS signed a cooperative agreement with the Nature Conservancy and the Air Force to restore and expand occupied habitat for the Stephens' kangaroo rat on March Air Force Base in southern California. The agreement called for the occupied habitat to eventually expand from several hundred acres to 600 acres (250 hectares), and eventually (possibly) to over 1,000 acres (400 hectares). The California Transportation District contributed $1.5 million to fund the habitat restoration in compensation for habitat loss from the development of a Federal highway on the base. The interest from this money is being used for managing the species.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

References

Bleich, B. C. 1977. Dipodomys stephensi. Mammalian Species. American Society of Mammalogists.

Lackey, J. A. 1967. "Growth and Development of Dipodomys stephensi. " Journal of Mammalogy 48:624-632.

Thomas, J. R. 1973. "Stephens' Kangaroo Rat Survey." California Department of Fish and Game, Sacramento.