Perception Channels: tactile ; chemical
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).
US Federal List: threatened
CITES: no special status
IUCN Red List of Threatened Species: endangered
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.
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.
Stephen's kangaroo rats are granivores. Seeds are collected in cheek pouches and stored in either shallow holes or nesting burrows (Storer, 1963).
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).
Biogeographic Regions: nearctic (Native )
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).
Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral
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).
Average mass: 65 g.
Other Physical Features: endothermic ; bilateral symmetry
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)
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Stephens's kangaroo rat (Dipodomys stephensi) is a species of rodent in the family Heteromyidae.[2] It is endemic to the Southern California region of the United States, primarily in western Riverside County.[3] The species is named after American zoologist Frank Stephens (1849–1937).[4]
The natural habitat of Stephens's kangaroo rat is sparsely vegetated temperate grassland.[5] This habitat has been destroyed or modified for agriculture throughout the species' range; as a result, Stephens's kangaroo rat is listed as an threatened species[6] by the U.S. Fish and Wildlife Service. It occurs sympatrically with the agile kangaroo rat, but tends to prefer few shrubs and gravelly soils to the agile's preference for denser shrubs.[7]
This kangaroo rat is part of the Dipodomys genus. Despite the common name, this is unrelated to an Australian kangaroo (Macropodidae). It is a medium size for its genus at 277 to 300mm in total length and an average weight of 67.26g. Its tail length is 164 to 180mm, which puts the tail about 1.45 times the length of the body. The color is described as being bicolored with tan to dark brown on the dorsal side and white on the ventral side. The soles of the hind limbs have a dusky color to them, there are a few white hairs on the tufts of the tail, and there are ventral and dorsal white stripes that run along the tail.[5]
Stephens's kangaroo rat was once found in limited regions in southern California,[8] but now due to development leading to habitat loss the populations are now only found in select nature reserves in San Jacinto Valley, San Bernardino, and northwestern San Diego counties in California.[5] Roads surround all the locations that they live or are found to live. This creates problems if they are paved and used often because of car fatalities. However, the Stephens's kangaroo rat has been found to inhabit and colonize dirt roadsides. This may be due to the type of habitat they prefer.[8] The Stephens's kangaroo rat prefers sparsely vegetated areas, about 15% cover,[9] that have annual grasslands with low shrub cover of sagebrush. Further more they like seral stage, intermediate, plant communities that are retained by fires, grazing, and or agriculture. They are also limited to gravely soil that cannot be too dense. This is because they have to burrow into it to make their tunnel systems for nesting and storage.[8]
With living in sparsely covered habitat and making bare spots in the land the rats create trails. They use these trails to get around easily from food source to food source. These trails lessen some of the dangers of foraging, as they make for a clear path for fast getaways leading straight to their burrow. Even though they move along their cleared trails to go to different food sources and the use to escape terrestrial predators they have to worry about aerial predators. They deal with this by foraging under the remaining shrubs that are left standing for seeds.[10] Seeds are the on the main course for this kangaroo rat, and that means that they are a granivorous. In doing dissection of kangaroo rat stomachs it was found that their diets composed of red brome (Bromus rubens), common Mediterranean grass (Schismus barbatus), and red-stemmed filaree (Erodium cicutarium). All of these species were introduced to North America. Ants, chewing lice, and darkling beetles were also found in their stomachs but not as prominent as the plant species listed above.[11]
Stephens's kangaroo rats have been shown to have a keystone like effect on their sounding environment. One way this is seen is by digging burrows. By digging burrows the soil fertility increases and the water infiltration increase as well. This then leads to larger plant diversity. Seed caching is also another means of how they change their environment. Seed caching is when they bury seeds to hide them so they can come back later for them. They don't always find them again or eat them and this leads to a greater diversity of plants around their burrow. Erodium, which is an invasive species, is able to outcompete native species. This then diminishes the natural diversity within the habitat. Stephens's kangaroo rat is able to help decrease the impact by controlling the impact of the Erodium by keeping the numbers down. These kangaroo rats clear patches of ground, which allows it to keep a seral stage environment. This removal of vegetation also keeps down the number of granivorous rodents down. This then allows for plants to have a greater chance to disperse and reach full development.[12]
Due to the dispersal and location of the populations of kangaroo rats they have experienced isolation from other populations. In two populations a haplotype, haplotype A, was found, but it was not found in a populations further away. This suggests that there is a decrease of gene flow between the different populations of kangaroo rats. Another haplotype type designates a different story as to the genetics of this species. A haplotype CC is widespread but not in a random fashion. The haplotype CC mostly dominates in the south with very little appearance in the north and central regions. This high frequency of haplotype CC in the south and the lack of different haplotypes unrelated to haplotype CC suggest that there was a population bottleneck that occurred in the south. It seem likely that the population of southern Kangaroo rats now would have repopulated from a small group in the south due to them living in a disconnected valley from the central and northern populations.[13]
Stephens's kangaroo rat (Dipodomys stephensi) is a species of rodent in the family Heteromyidae. It is endemic to the Southern California region of the United States, primarily in western Riverside County. The species is named after American zoologist Frank Stephens (1849–1937).
The natural habitat of Stephens's kangaroo rat is sparsely vegetated temperate grassland. This habitat has been destroyed or modified for agriculture throughout the species' range; as a result, Stephens's kangaroo rat is listed as an threatened species by the U.S. Fish and Wildlife Service. It occurs sympatrically with the agile kangaroo rat, but tends to prefer few shrubs and gravelly soils to the agile's preference for denser shrubs.
