Animal Info - Stephens' Kangaroo Rat

Dipodomys stephensi

Status: Lower Risk - Conservation Dependent

1. Profile (Picture)
2. Tidbits
3. Status and Trends (IUCN Status, Countries Where Currently Found, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Weight, Habitat, Age to Maturity, Gestation Period, Birth Season, Birth Rate, Early Development, Diet, Behavior, Social Organization, Density and Range)
5. References

Profile

Pictures: Stephens' Kangaroo Rat #1 (9 Kb GIF) (Calif. Fish & Game); Stephens' Kangaroo Rat #2 (16 Kb JPEG); Stephens' Kangaroo Rat #3 (59 Kb JPEG) (Univ. Calif.)

Stephens' kangaroo rat weighs about 65 g (2.3 oz). Within its range, Stephens' kangaroo rat occurs at elevations below about 610 m (2000') in flat or gently rolling, often degraded, annual grassland. Rainfall is an important factor in its ecology: densities of Stephens' kangaroo rat show 10-fold fluctuations in population density related to regional rainfall. Stephens' kangaroo rat eats seeds and is nocturnal. Adults are solitary and are characterized by a promiscuous mating system and no persistent pair bonds.

Stephens' kangaroo rat was first described in 1907. Its entire geographic range, estimated at several thousand sq km (about 1000 sq mi), is centered in the San Jacinto and Perris Valleys of western Riverside County, California, USA, with minor extensions south into San Diego County and north into San Bernardino County.

By 1938, only about 37% of its original habitat was estimated to have remained, and its range had become greatly fragmented. Accelerating urban development has led to a further degradation in available habitat. Currently its remaining habitat occurs as small isolated patches embedded in rocky outcrops unsuitable for cultivation or as relatively extensive patches in protected watersheds (Price & Kelly 1994). Only 5% of its original habitat remains, although it still occupies a large area that has been partially protected through various agreements (Nowak 1999).

Stephens' kangaroo rat's decline was caused by habitat loss due to agriculture and development. It is currently threatened by urban development, although conservation agreements have apparently diminished this threat for the time being.

Tidbits

*** Kangaroo rats seldom drink water, since they are able to use water resulting from the chemical breakdown of their food. They conserve moisture by coming out of their burrows at night when the humidity is highest. They have kidneys at least 4 times as efficient as those of humans, and thus need much less water to remove wastes. (Nowak & Paradiso 1983)

*** Stephens' kangaroo rat is known to invade cultivated fields in suitable locations once plowing ceases (Price & Endo 1989).

*** Kangaroo rats travel by hopping on their hind legs. When threatened, they can hop 2 m (6.6') or more with one hop.

*** Bathing in dust is apparently necessary for the well-being of kangaroo rats. When they are not able to do so, captive kangaroo rats develop sores on their body and their fur becomes matted from oily secretions on their back. (Nowak 1999)

Status and Trends

IUCN Status:

1994: Endangered
1996 - 2004: Lower Risk - Conservation Dependent (IUCN 2004)

The assignment of Stephens' kangaroo rat to "Lower Risk - Conservation Dependent" is based on the assumption that the Habitat Conservation Action Plan, prepared for this species by officials of Riverside County, California, has provided sufficient preserve sites and will be fully implemented (IUCN 2004).

Countries Where Stephens' Kangaroo Rat Is Currently Found:

2004: Occurs in USA (California) (IUCN 2004).

History of Distribution:

Stephens' kangaroo rat was first described in 1907. Its entire geographic range, estimated at 2870 sq km (1100 sq mi), is centered in the San Jacinto and Perris Valleys of western Riverside County, California, USA, with minor extensions south into San Diego County and north into San Bernardino County.

By 1938, only about 37% of its original habitat remained, and it had become greatly fragmented. Accelerating urban development has led to a further degradation in available habitat. Currently its remaining habitat occurs as small isolated patches embedded in rocky outcrops unsuitable for cultivation or as relatively extensive patches in protected watersheds (Price & Kelly 1994). Only 5% of its original habitat remains, although it still occupies a large area that has been partially protected through various agreements (Nowak 1999).

Distribution Map #1 (3 Kb GIF) (Smith. Inst.)
Distribution Map #2 (12 Kb) (NatureServe Expl.)

Threats and Reasons for Decline:

Stephens' kangaroo rat's decline was caused by habitat loss due to agriculture. It is currently threatened by urban development, although conservation agreements have apparently diminished this threat for the time being.

Data on Biology and Ecology

Weight:

Stephens' kangaroo rat weighs about 65 g (2.3 oz).

Habitat:

Within its range, Stephens' kangaroo rat occurs at elevations below about 610 m (2000') in flat or gently rolling, often degraded, annual grassland. Trapping showed that it is associated with locations where grass cover and bare ground are abundant but where bush and rock are uncommon. (It is replaced on steeper slopes and in shrublands by a morphologically similar kangaroo rat, D. agilis.) Rainfall is an important factor in its ecology: densities of Stephens' kangaroo rat (and similar seed-eating species) show 10-fold fluctuations in population density positively correlated with regional rainfall. (Price & Endo 1989; Goldingay & Price 1997)

Stephens' kangaroo rat is found in the California Floristic Province Biodiversity Hotspot (Cons. Intl. 2005).

Age to Maturity:

3 months. 55 g (2.0 oz) is the minimum weight observed for lactating females (Price & Kelly 1994).

Gestation Period:

30 days.

Birth Season:

Reproductively active individuals have been found in every month of the year, although onset of estrus in females appears to be triggered by the start of winter rains (a pattern typical of kangaroo rats) and estrous cycling ceases after plants disperse seeds (Price & Kelly 1994).

Birth Rate:

The number of young per litter averages about 2.5.

Early Development:

Weaning takes place at 18 - 22 days.

Diet:

Stephens' kangaroo rat eats seeds.

Behavior:

Stephens' kangaroo rat is nocturnal.

Social Organization:

Stephens' kangaroo rat is solitary and is characterized by a promiscuous mating system and no persistent pair bonds, as has been reported in other kangaroo rats (Price & Kelly 1994). Kangaroo rats are usually strongly territorial, with 1 adult per burrow.

Density and Range:

Population density:

7.5 - 57.5 individuals/hectare (3 - 23 individuals/acre) (Nowak & Paradiso 1983)

4.9 - 5.2 individuals/hectare (2 - 2.1 individuals/acre) (Price & Endo 1989)

10 - 34 individuals/hectare (4 - 13.6 individuals/acre) (Price & Kelly 1994)

Range:

Individual home ranges of 420 - 1600 sq m (4500 - 17,000 sq ft) have been reported. (Nowak & Paradiso 1983)

Based on radio-implanted individuals, the area of the average home range corresponded to a circle with a radius of 20 m (66') (i.e. 1260 sq m (13,500 sq ft)) (Price & Kelly 1994)

References

Calif. Fish & Game, Cons. Intl. 2005, Goldingay & Price 1997, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, Lidicker 1989, NatureServe Expl., Nowak 1999, Nowak & Paradiso 1983, Price & Endo 1989, Price & Kelly 1994, Smith. Inst., Univ. Calif.

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Last modified: March 11, 2005;