Dipodomys merriami
Merriam's kangaroo rat

Dipodomys merriami, Merriam's kangaroo rat, is a rodent found in the arid regions of the southwest United States and Mexico.

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.

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 ).

Merriam's kangaroo rats are solitary,nocturnal mammals. They stay in their burrow during the day. The burrow is a shallow opening in the ground, usually near the base of shrubs. One adult occupies each burrow system. They are active during the night. D. merriami are aggressive amoung their own species. They seem to have two major time periods of activity: one around 9 PM, and the other about 3 AM, when there is the most moisture in the air. ( http://www.desert.usa.com/aug96/du_krat.html ). When they are cornered by a predator, kangaroo rats kick sand in the face of the attacker. Another defense is to jump up and down on their hind legs. They collect and disperse seeds much of the time that they are out of their burrows. Their digging aerates the soil.

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

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 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.

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 ).