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Tipton kangaroo rat
Dipodomys nitratoides nitratoides

Status

U.S.A. and California Endangered

Life History

The Tipton kangaroo rat is one of three subspecies of the San Joaquin kangaroo rat (Dipodomys nitratoides). Tipton kangaroo rats are visually similar to other kangaroo rats; they have a tawny yellow head and back with a white belly and a white stripe on the elongated hind legs that continues down the sides of the otherwise black tail. Other characteristics include: a large head, compared to other rodents, with large dorsally-placed eyes and small rounded ears; small forelegs with strong claws; and a long, tufted tail.

Tipton kangaroo rats eat mostly seeds, but will supplement their diet with green, herbaceous vegetation and insects when available. Most aspects of food and foraging of Tipton kangaroo rats are identical to those of Fresno kangaroo rats, Dipodomys nitratoides exilis.

Little specific information is available on the reproduction of Tipton kangaroo rat. In general, this aspect of their biology is similar to that of the Fresno kangaroo rat. Reproduction occurs in the winter months with most females giving birth to only one litter of two young. Some females born early in the year may breed when about 12 weeks old.

Tipton kangaroo rats inhabit arid-land vegetative communities with level or nearly level terrain located within the floor of the Tulare Basin in the southern San Joaquin Valley. Many of the presently inhabited areas have one or more species of woody shrubs, such as saltbush, iodine bush, goldenbush, and honey mesquite, sparsely scattered throughout and a ground cover dominated by introduced and native grasses and forbs. Burrows are commonly located in slightly elevated mounds, the berms of roads, canal embankments, railroad beds, and bases of shrubs and fences where wind-blown soils accumulate above the level of surrounding terrain. Soft soils, such as fine sands and sandy loams, and powdery soils of finer texture and of higher salinity generally support higher densities of Tipton kangaroo rats than other soil types. Terrain not subject to flooding is essential to sustain a population of Tipton kangaroo rats. The placement of burrows on elevated grounds in flood-prone areas is important, but depending on the extent and duration of the flooding, those burrows and populations may still be adversely affected.

Distribution

Historically, Tipton kangaroo rats were distributed from the southern margins of Tulare Lake on the north and eastward and southward along the edge of the San Joaquin Valley floor in Tulare and Kern counties to the foothills of the Tehachapi Mountains. The westward edge of their ranges were the marshes and open water of Kern and Buena Vista lakes and the sloughs and channels of the Kern River alluvial fan.

Current distribution is not completely known-occurrences of the Tipton kangaroo rats are limited to scattered, isolated clusters west of Tipton, Pixley, and Earlimart and in areas in southern Kern County. Cultivation and urbanization has reduced much of the area historically inhabited. However, in recent years, Tipton kangaroo rats have reinhabited several hundred acres that were formerly in crop production but were retired and allowed to go fallow due to drainage problems, or lack of water, or were acquired by state or federal government as wildlife habitat.

Classification

Order RODENTIA, Suborder SCIUROGNATHI, Family HETEROMYIDAE, Genus Dipodomys, Species nitratoides

Subspecies

D. n. nitratoides, Tipton kangaroo rat, is one of the three subspecies of the San Joaquin kangaroo rat. The other two subspecies are: D. n. exilis, Fresno kangaroo rat, and D. n. brevinasus, short-nosed kangaroo rat.

Recent Synonyms

None.

Other Common Names

None.

References

Hoffmann, W. M. 1975. Geographic variation and taxonomy of Dipodomys nitratoides from the California San Joaquin Valley. M.A. thesis, California State Univ., Fresno, 75pp; Williams, D. F. and D. Germano. 1992. Recovery of endangered kangaroo rats in the San Joaquin Valley, California. Trans. West. Sect. Wildl. Soc. 28:93-106; Williams, D. F., and K. S. Kilburn. 1992. The conservation and status of the endemic mammals of the San Joaquin faunal region, California. Pp. 329-345, in Endangered and sensitive species of the San Joaquin Valley, California: their biology, management, and conservation (D.F. Willliams, S. Byrne, and T.A. Rado, eds.).

Size

Total length (average):
males: 235 mm (9.25 in)
females: 231 mm (8.7 in)

Weight (range for both sexes):
35-38 g (1.23-1.34 oz)
Length of hind foot (average):
males: 34.7 mm (1.37 in)
females: 33.6 mm (1.32 in)

Identification

The San Joaquin kangaroo rat can be distinguished from other kangaroo rats within its geographic range by the presence of four toes on its hind foot; the other species in the area have five toes. The Tipton kangaroo rat is intermediate in size between the other two subspecies of D. nitratoides. Individuals of the three subspecies cannot be reliably distinguished without dissection unless the geographic location of the individual is known.

Authors of Profile

N. L. Brown and D. F. Williams

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