Predators of Dipodomys merriami include rattlesnakes, coyotes, weasels, owls, and predatory birds ( Grzimek, 1990 ). D. merriami have the ability to efficiently use the water from their food, and they neither sweat nor pant to keep cool. They have specialized kidneys which allow them to dispose of waste material with very little output of water. This allows them to live comfortably in arid areas ( http://www.desert.usa.com ).
Perception Channels: tactile ; chemical
The subspecies Dipodomys merriami parvus (San Bernardino Merriam's kangaroo rat) is considered endangered under the U.S. Endangered Species Act. Several factors contribute to this, including predation and habitat reduction resulting from agricultural development, urbanization, and road-building. Flooding has also been a contributing factor. The only known method for conserving the kangaroo rat is through habitat preservation. The U.S. Fish and Wildlife Agency, together with the State of California and other wildlife agencies have purchased thousands of acres of habitat to try and protect these animals. This is a slow project because recovery plans are expensive ( http://www.hillsborough.k12.nj.us/hhs/endspeci/KANGARAT.HTM ).
San Bernardino Merriam's kangaroo rats (Dipodomys merriami parvus and Earthquake Valley kangaroo rats (Dipodomys merriami collinus), which both occur near the Los Angeles and San Diego urban areas, are considered data deficient by the IUCN.
Other subspecies of D. merriami are not considered threatened currently.
US Federal List: endangered; no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
As seed predators they may affect plant populations, but they are rare in agricultural areas.
Dipodomys merriami are important in dispersing seeds of plants in arid regions. Their burrowing and digging is thought to aerate and fertilize soil. (www.desert.usa.com/aug96/du_krat.html )
The diet of the Merriam's kangaroo rat is almost entirely seeds. They feed primarily on the seeds of mesquite, creosote bush, ocotillo, purslane, and grama grass. One study of D. merriami showed that seeds make up 64% of the diet, with seeds of shrubs consituting 23%, forbs 24%, those of grasses 4.5%, and those of scculent plants 12%. ( http://www.nsrl.ttu.edu/tmot/dipoerr.htm ). The diet is diverse and varies seasonally. Insects are eaten occasionally. They are eaten in the greatest abundance in the winter months, while green vegetation is eaten most during the mid-summer months
Dipodomys merriami, Merriam's kangaroo rat, is a rodent found in the arid regions of the southwest United States and Mexico.
Biogeographic Regions: nearctic (Native )
Dipodomys merriami are sand-dwelling mammals that inhabit arid regions of the southwestern United States and Mexico. Habitat requirements of Merriam's kangaroo rats are less strict than most other species of kangaroo rats. They can live equally well in sandy soils, clays, gravels, and among rocks. (www.nsrl.ttu.edu/tmot/dipomerr.htm ). Compared to other kangaroo rats, Dipodomys merriami inhabits harder, stonier soils.
Terrestrial Biomes: desert or dune
Range lifespan
Status: captivity: 9.7 (high) years.
Merriam's kangaroo rats have an average total length of 247 mm. The tail is rather long, about 144 mm in length, with an end tassle. It is usually more than 130% of the the length of the head and body. ( http://www.nsrl.ttu.edu/tmot/dipomerr.htm ). The body is covered with dusky stripes which run the length of the head and body. The skull is sciuromorphous with dramatically inflated auditory bullae. The face is covered with dark facial markings. D. merriami also has fur lined external cheek pouches which it carries seeds in. The belly of Merriam's kangaroo rat bears white, silky pelage. The hind feet, bearing four toes, are very large, (39 mm), with hairy soles. These hairy soles aid the kangaroo rat in jumping through loose sand. The forelegs are retrogressed. The ears are small and hairless, and the eyes are large and luminous, similar to the eyes of other nocturnal mammals. The dental formula is 1/1, 0/0, 1/1, 3/3 = 20. ( Vaughn, 1999 ).
Range mass: 40 to 50 g.
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 0.246 W.
Dipodomys merriami has a high reproductive rate. Breeding for the Merriam's kangaroo rat begins in early February and continues into the spring, at least through May. The gestation period is approximately 28 to 32 days. Between one and six young are born in each litter, with an average of three. When young are born they weigh between 3 and 8 grams. The young are weaned after 15-25 days, and sexual maturity is reached between 60-84 days. They can live up to 9.8 years. Average territory size for males is 67,300 square feet, less than one acre. Average female territories are 4000 square feet. (Grzimek, 1990, www.desert.usa.com/aug96/du_krat.html )
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Average birth mass: 2.92 g.
Average gestation period: 28 days.
Average number of offspring: 2.3.
Average age at sexual or reproductive maturity (female)
Sex: female: 102 days.
