Dipodomys stephensi
Stephens's kangaroo rat

Dipodomys stephensi are commonly called Stephen's kangaroo rats. This species of kangaroo rat is confined to a relatively small geographical range, approximately 1,100 square miles. They can be found in North America, in Riverside County through northern San Diego County, in the state of California ( http://ecoregion.ucr.edu/mshcp/full.asp?sp_num=6308).

Stephen's kangaroo rats are found in arid and semi-arid habitats with some grass or brush. They prefer open habitats with less than 50% protective cover. They require soft, well-drained substrates for building burrows and are typically found in areas with sandy soil. ( http://ecoregion.ucr.edu/mshcp/full.asp?sp_num=6308).

Total body length in Stephen's kangaroo rats, from the head to the tip of the tail, can be up to 330 mm. The tail can be twice as long as the body. The relatively bare tail ends with a tuft of dark and white fur. Stephen's kangaroo rats have large hind feet which are used for jumping. The body is covered with light brown fur which becomes lighter on the ventral surface and legs. Ears are small and lay back against the head. Eyes are large, which is an important adaptation for these nocturnal creatures (Storer, 1963 ; http://www.desertusa.com/aug96/du_krat.html).

Kangaroo rats have several remarkable adaptations to desert life. Their large ears and enlarged auditory bullae permit keen hearing and the perception of low frequency sounds. These adaptations allow Stephen's kangaroo rats to avoid nocturnal predators such as owls or rattlesnakes (Raven, 1999).

Kangaroo rats also use water very efficiently. Most mammals obtain water through drinking and food consumption. Stephen's kangaroo rats have specialized kidneys that produce highly concentrated urine. As a result, Stephen's kangaroo rats are never required to drink water because a sufficient amount is obtained through food and metabolic activity (Raven, 1999).

Breeding occurs twice a year, in summer and in winter. Each year Stephen's kangaroo rats produce, on average, 5 young. Numbers of young per litter is correlated with amount of rainfall, higher rainfall resulting in higher litter size. The gestation period is approximately 30 days with weaning occuring between 18 to 22 days after birth. Offspring are born in enlarged burrows, which often double as locations of food storage. Age of sexual maturity is estimated to be acheived at 3 months, and females must weigh 55 g before they can produce milk.

( http://ecoregion.ucr.edu/mshcp/full.asp?sp_num=6308 ; http://www.animalinfo.org/species/rodent/dipostep.htm ; Storer, 1963)

Stephen's kangaroo rats are nocturnal and are not sexually dimorphic. All members are solitary and maintain asymmetrical territories which often overlap with related species of rodents. The time of most activity occurs between 9 P.M and 3 A.M. Males and females do not form a pair bond and males do not contribute to raising young.

Kangaroo rats travel primarily by saltatory locomotion, they use their long hind feet to hop and can acheive high speeds in this manner. Each individual hop may be up to 2 meters long. Only when an animal is moving slowly will it use its forelimbs.

Dustbathing is vital to the health of kangaroo rats. When prevented from dustbathing their fur becomes matted and unhealthy and they develop sores on their body.

( http://ecoregion.ucr.edu/mshcp/full.asp?sp_num=6308 ; http://www.ocregister.com/science/features/edgeofnature/stephenskangaroorat.shtml)

Stephen's kangaroo rats are granivores. Seeds are collected in cheek pouches and stored in either shallow holes or nesting burrows (Storer, 1963).

Stephen's kangaroo rats are important in maintaining the ecological integrity of arid and semi-arid habitats where they occur. They modify habitats by impacting the structure of vegetation and they serve as important prey sources for raptors, foxes, coyotes, and other predators.

The feeding habits of Stephen's kangaroo rats causes a decrease in the grass and shrub density. Research indicates that "their removal from plots resulted in the habitat converting from desert shrub to grassland".

Stephen's kangaroo rats may take enough grain from neighboring agricultural fields to be important economically but generally they do not adversely affect human populations.

( http://ecoregion.ucr.edu/mshcp/full.asp?sp_num=6308).

Currently, Stephen's kangaroo rats are listed as threatened under the Endangered Species Act of the United States. Farming is the number one threat to Stephen's kangaroo rats because it limits food availability and destroys burrows. Development for agriculture has resulted in a loss of 95% of appropriate habitat for Stephen's kangaroo rats. Overgrazing by domesticated animals, such as horses and cattle, also limits the food supply.

( http://ecoregion.ucr.edu/mshcp/full.asp?sp_num=6308).