Tipton Kangaroo Rat

Dipodomys nitratoides nitratoides

Description

The Tipton kangaroo rat, Dipodomys nitratoides nitratoides, has a head and body length of about 3.9-4.3 in (10-11 cm) and a tail length of 4.8-5.3 in (12.5-13 cm). It is dark yellowish tan above and has a white underbelly. A white stripe extends across each flank and along the sides of the tail. It has large, protruding eyes and very small front legs. It uses its large hind legs to hop, much like a kangaroo. The Tipton kangaroo rat is larger than the Fresno kangaroo rat.

This kangaroo rat was first described as a sub-species of D. merriami, Merriam's kangaroo rat. In 1920-1921 it was changed to a subspecies of the Fresno kangaroo rat, which is its present classification.

Behavior

Tipton kangaroo rats are nocturnal and feed on seed grains and green parts of plants, which they transport in cheek pouches formed from folds of fur-lined skin that stretch back as far as the neck. They occasionally eat insects.

Kangaroo rats breed all year. Gestation is four to five weeks; litters contain up to five young, which leave the nest after about six weeks. One female can bear as many as three litters a year.

Foraging and breeding patterns of the Tipton and Fresno kangaroo rats are identical. See the account of the Fresno kangaroo rat for more details.

Habitat

The Tipton kangaroo rat inhabits saltbrush scrub and sink scrub. Plants in these sparsely vegetated communities include iodinebush, saltbush, Mormon-tea, red sage, and sea blite. This kangaroo rat is found in soft, friable soil in and around lakebed areas that escape seasonal flooding. It digs shallow burrows around the base of shrubs where wind-deposited soils have accumulated.

Distribution

The historic range once encompassed about 1.7 million acres (695,000 hectares) in the San Joaquin Valley in California. This area extended from Hanford (Kings County) in the north, south to Arvin (Kern County).

As of July 1985, only about 63,000 acres (25,000 hectares), encompassing 3% of its historic range, were still occupied by the Tipton kangaroo rat. About 10% of the current range is public land and includes the Pixley National Wildlife Refuge, Allensworth Ecological Preserve, and lands administered by The Nature Conservancy at the Paine Wild-flower Preserve. Since 1985, some acreage has been reclaimed and other acreage lost, so that the total suitable habitat acres is at its 1985 level.

At Pixley National Wildlife Refuge, Tipton kangaroo rats are the most numerous small mammal.

Threats

The primary threat to the Tipton kangaroo rat is the conversion of large areas of its historic range to agricultural use. Other reasons for the species' decline have been the construction of roads, canals, and railroads, as well as residential and commercial development. Many of the populations are isolated from each other, resulting in inbreeding.

Furthermore, because populations are so small and are typically surrounded by agricultural lands with their attendant chemicals and disturbances, the Tipton kangaroo rat is vulnerable to extirpation by a single catastrophic event, including floods, disease, predation, and rodentcides. It may also become the victim of programs aimed at controlling other species, not the kangaroo rat, such as the California ground squirrel.

Conservation and Recovery

Populations are on public land at Pixley National Wildlife Refuge and at Allensworth Ecological Preserve, and on private lands administered by The Nature Conservancy. These habitats are relatively secure and are managed with the welfare of the kangaroo rat in mind. Most of these lands are unsuitable to farming because of heavy seasonal rains. However, it is estimated that the minimum area for supporting a viable reproducing population is from 800 to 3,000 acres (325 to 1,214 hectares), and most of the fragmented habitat areas are too small to support long-term survival of the Tipton kangaroo rat. The goal of the conservation effort is to secure more suitable habitat.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232
http://pacific.fws.gov/

References

Eisenberg, J. F. 1963. "The Behavior of Heteromyid Rodents." University of California Publications in Zoology 69:1-100.

Grinnell, J. 1920. "A New Kangaroo Rat from the San Joaquin Valley, California." Journal of Mammalogy 1:78-179

Grinnell, J. 1921. "Revised List of the Species in The Genus Dipodomys. " Journal of Mammalogy 2:94-97.

Rado, Ted. 1988. "Determination of Endangered Status for the Tipton Kangaroo Rat." Federal Register 53(131):25606-25611.