Giant Kangaroo Rat (Dipodomys ingens)
General Distribution
Giant kangaroo rat's range approaches and potentially extends onto the Los Padres National Forest at the lower end of the Cuyama Valley. Although the Los Padres National Forest has conducted limited surveys in northern Santa Barbara and eastern San Luis Obispo Counties, no documented sightings of this species have been found on National Forest System lands in southern California. Forest Service modeled habitat (USDA Forest Service 2000) shows less than 2000 acres of potential habitat present on National Forest System lands. However, giant kangaroo rats could inhabit portions of the Los Padres National Forest adjacent to the Cuyama Valley (U.S. Fish and Wildlife Service 2001).
Systematics
Giant kangaroo rat is in the family Heteromyidae; 21 species are recognized in the genus Dipodomys. Giant kangaroo rat is the largest of all the kangaroo rats (U.S. Fish and Wildlife Service 1998). There are no recognized subspecies.
Habitat Requirements
Giant kangaroo rats inhabit native annual grassland and shrubland habitats on level and gently sloping ground with sandy, well-drained soils of valley floors and adjacent gentle slopes. Their habitat is vegetated with annual grasses and forbs and widely scattered desert shrubs. It occurs at elevations of approximately 280–2,800 feet (85–853 meters) but is rare above 2,400 feet (731 meters) (Williams 1996). Long-term occupancy of a site by giant kangaroo rats results in a Mima-mound topography, with burrow systems located in mounds a few to several centimeters higher than the intervening ground (Williams 1996).
Reproduction
Giant kangaroo rat has an adaptable reproductive pattern that is affected by both population density and availability of food. During times of high population density, female giant kangaroo rats have a short winter reproductive season with only one litter, and there is no breeding by young-of-the-year (U.S. Fish and Wildlife Service 1998). During times of low population density the breeding season can extend into August or September. In most years females are reproductive between December and March or April. Gestation lasts 30–35 days (U.S. Fish and Wildlife Service 1998). Litter size for this species ranges from 4–6 (Zeiner and others 1990). Under favorable conditions, some females can produce 2–3 litters per year. Young are born and reared in the burrows.
Daily/Seasonal Activity
Giant kangaroo rats are primarily nocturnal and are active throughout the year. They typically emerge from burrows shortly after sunset and forage on the surface until near sunrise, although most activity occurs in the first 2 hours after dark. Activity increases in the spring when seeds of annual plants are ripe and available (U.S. Fish and Wildlife Service 2001).
Diet and Foraging
Giant kangaroo rats subsist almost entirely on the seeds of annual plants such as brome grasses (Bromus spp.) and filaree (Erodium spp.), but also consume green vegetation, especially during the spring (U.S. Fish and Wildlife Service 1998). Seeds are harvested mostly during the spring and winter when they are dry and are cached in large quantities in burrows or buried in small, shallow holes at the surface (Shaw 1934). Giant kangaroo rats harvest, stack, and dry caches of grasses and forbs near the entrance of their burrows. Ripening heads of grasses and forbs are cut and cured in small surface pits located on the area over their burrow system and covered with a layer of loose, dry dirt. Some individuals also create large stacks of seed heads, which are cured at the surface of the burrow system before being transported underground.
Territoriality/Home Range
Giant kangaroo rat territories average 20 feet (6 meters) in diameter. Each kangaroo rat maintains and defends an individual territory in a colony that may consist of from two to thousands of precincts (core areas within territories). Giant kangaroo rat home ranges vary from about 645–3,768 square feet (60– 350 square meters), with no significant size difference between sexes (U.S. Fish and Wildlife Service 1998).
Predator-Prey Relations
When abundant, giant kangaroo rat is a significant prey item for many predators, including San Joaquin kit fox (Vulpes macrotis mutica), American badger (Taxidea taxus), coyote (Canis latrans), long-tailed weasel (Mustela frenata), burrowing owl (Athene cunicularia), barn owl (Tyto alba), great horned owl (Bubo virginianus), and short-eared owl (Asio flammeus). Snakes observed within giant kangaroo rat colonies include coachwhip (Masticophis flagellum), gopher snake (Pituophis melanoleucus), common king snake (Lampropeltis getulus), and western rattlesnake (Crotalus viridis). Giant kangaroo rat may also be preyed on by blunt-nosed leopard lizards (Gambelia sila) and San Joaquin antelope squirrels (Ammospermophilus nelsoni) (U.S. Fish and Wildlife Service 1998).
Literature Cited
Garrison, T.E.; Best, T.L. 1990. Dipodomys ordii. Mammalian Species 353: 1-10.
Shaw, W.T. 1934. The ability of the giant kangaroo rat as a harvester and storer of seeds. Journal of Mammalogy 15: 275-286.
USDA Forest Service. 2000. Southern California consultation package for forest plans. U.S. Fish and Wildlife Service. 1998. Recovery plan for the San Joaquin Valley upland species. Portland, OR.
U.S. Fish and Wildlife Service. 2001. Biological and conference opinions on the continued implementation of land and resource management plans for the four southern California national forests, as modified by new interim management direction and conservation measures (1-6-00-F-773.2).
Williams, D.F. 1992. Geographic distribution and population status of the giant kangaroo rat, Dipodomys ingens (Rodentia, Heteromyidae). In: Williams, D.F.; Byrne, S.; Rado, T.A., eds.
Endangered and sensitive species of the San Joaquin Valley, California: Their biology, management, and conservation. Sacramento, CA: The California Energy Commission.
Williams, D.F. 1996. Giant kangaroo rat, Dipodomys ingens. [Online]. Available: http://esrp.csustan. edu/.
Zeiner, D.C.; Laudenslayer, W.F., Jr.; Mayer, K.E.; White, M., eds. 1990. California's wildlife. Volume III. Mammals. Sacramento, CA: California Statewide Wildlife Habitat Relationships System, California Department of Fish and Game.
Information gathered from California DFG - California Interagency Wildlife Task Group