Giant kangaroo rat
Giant kangaroo rat
Dipodomys ingens, the giant kangaroo rat, is one of over 20 species of kangaroo rats, which are small members of the rodent family. The giant kangaroo rat is the largest of the kangaroo rats, measuring about 15 cm (6 in.) in length, including its long, tufted tail. It is tan or brown in color. Like other kangaroo rats it has a large head and large eyes, and long, strong hind legs with which it can hop at high speeds.
The Giant Kangaroo Rat has been recently added to the endangered species list due to its habitat being severely reduced. Data was collected on its foraging behavior and social structure. Traps baited kangaroo rats with oats in them for four weeks in the summer. The animals were captured, tagged with tracking devices and set free. Results show that significantly fewer males were captured. This could have been due to the time of year at which the experiment was tested. Females were found to be more social. Studies also showed that the kangaroo rat’s den is the area in which the animal spends the most time.
The giant kangaroo rat lives on dry, sandy grasslands and digs burrows in loose soil. It lives in colonies, and the individuals communicate with each other by drumming their feet on the ground. These foot thumping signals range from single, short thumps to long, drawn out “footrolls” that can average over 100 drums at 18 drums per second. These audible signals serve both as a warning of approaching danger, as a territorial communication, and to communicate mating status.
In the spring and summer, individuals generally spend less than two hours of the night foraging above ground. They are very territorial and never leave their den for more than 15 minutes per day. The giant kangaroo rat then stores the seeds in a larder for later eating and gives birth to a litter of 1 to 7 babies, with an average of 3 per litter. It communicates with potential mates by sandbathing, where the giant kangaroo rat rubs its sides in sand, leaving behind a scent to attract mates. They live for only 2–4 years.
This species was declared endangered on both the federal and California state levels in the 1980s. It inhabits less than a mere 2% of its original range and can now be found only in isolated areas west of the San Joaquin Valley, including the Carrizo Plain, the Elkhorn Plain, and the Kettleman Hills. The giant kangaroo rat, like many other rodent species, lost much of its habitat as the Central Valley fell under agricultural use. Much information still needs to be obtained regarding their basic biology and compatibility with various land uses before clear directives can be made. Besides some projects currently underway in the Carrizo Plain National Monument, studies need to be conducted on populations whose range overlaps with private lands.
Different seasons also affect the mating of the Giant Kangaroo Rat. During the summer, the male rats go out of their comfort zones and mate with neighboring female rats in order to expand their family. During the winter, the males stay in their original burrow and stay with females as well. Researchers use tables and pictographs to show the size of home ranges from the male and female rats during the winter and summer seasons. By taking a select number of male and female kangaroo rats from each season and studying their mating patterns, studies are able to determine whether the home-ranges overlap or not. It has been proven that the smaller the amount of rats in the study, the larger the overlapping of burrows. Also the larger amount of rats used for the study had their burrows spaced out. Therefore it is easy to believe that the amount of rats used for the study determined the home-ranges. If there is a large amount of rats being studied, then the burrows formed in order to mate will be spaced further apart by comparison to the space made by the small amount of rats used for the study. Because one of the studies used 7 kangaroo rats and another used over 20, there is more of a reason for the study of 20+ rats to have spread out burrows and the study of 7 rats to have overlapping burrows.
Endangered Giant Kangaroo Rat (Dipodomys ingens)) populations have become more dispersed and less numerous over time. This can have major side effects to the genetic diversity of the species. The D. ingens populations only cover about 3% of the territory of what they historically used to live in. Agricultural development has severely impacted the habitats of the D. ingens, and restricted it to several small isolated areas. Because of this, the D. ingens is at risk for genetic drift and inbreeding within smaller populations. The D. ingens lives in metapopulation structures due to their habitats being taken over by humans. They are divided into several small remnant populations that are unable to disperse over larger areas because of topographical limitations. This is a larger problem for northern subpopulations of D. ingens than those who live in the south. D. ingens is believed to be polygynous (one male, multiple females) but a common ratio between male and female partners has not yet been found. The study showed that translocation was a successful method for increasing diversity and population size of D. ingens.
According to information vetted by Los Padres Forest Watch, the GKR is a keystone species in the Carrizo Plain and probably elsewhere in the San Joaquin Valley. It provides food for predators and creates burrow systems used by other animals. It is important to recognize that GKR viability is not simply a matter of one obscure species, at all, but rather an integral cornerstone of the entire affected ecosystem. In the Carrizzo Plain, just outside the National Monument, GKR is in jeopardy due to several proposed massive solar installations as well as a mining proposal linked to the CVSR project.
- Linzey, A.V. & NatureServe (Williams, D.F. & Hammerson, G.) (2008). Dipodomys ingens. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 13 January 2009.
- Patton, J. L. (2005). "Family Heteromyidae". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 846. ISBN 978-0-8018-8221-0. OCLC 62265494.
- ARKive - images and movies of the Giant Kangaroo rat (Dipodomys ingens)
- link: Giant Kangaroo Rat
- The rat on PBS