Merriam's Kangaroo Rat
Order Rodentia : Family Heteromyidae : Dipodomys merriami Mearns

Description. A small, four-toed, usually buff-colored kangaroo rat; tail rather long, usually more than 130% of length of head and body, tip dusky, and dorsal and ventral dusky stripes usually present; length of head and body usually less than 105 mm; dark facial markings rather pale; underparts white; pelage "silky." External measurements average: total length, 247 mm; tail, 144 mm; hind foot, 39 mm. Weight, 40-50 g. Dental formula as in Perognathus flavescens.

Distribution in Texas. A rodent of the southwest; known in Texas primarily from the Trans-Pecos eastward to Gaines County in the north and Dimmit County in the south.

Habits. In its habitat requirements this species is more tolerant than most other species of kangaroo rats. It apparently can succeed equally well on sandy soils, clays, gravels, and even among rocks. Where merriami occurs with Dipodomys ordii or some other less tolerant and sand-dwelling kangaroo rat, merriami usually inhabits the harder, stonier soils. In Trans-Pecos Texas, this is the usual relationship — D. ordii is found in areas of loose sands; D. merriami in areas of clayey or stony soils which are not suitable habitat for the other species.

Their burrows are usually simple in design, shallow and with openings near the bases of shrubs. In these, the rats live in the daytime and rear their families. Usually, only one adult occupies each burrow system.

Their food is almost entirely seeds. Seeds of mesquite, creosote bush, purslane, ocotillo, and grama grass have been found in their cheek pouches, as well as green vegetation and insects. A study of D. merriami in the Guadalupe Mountains showed that seeds make up 64% of the diet, with seeds of shrubs constituting 23%, those of forbs 24%, those of grasses 4.5%, and those of succulent plants 12%. The diet varies seasonally but seeds, green vegetation, and insects are eaten throughout the year. Green vegetation is most important in mid-summer, while insects are eaten in greatest abundance in winter.

Breeding begins in February and continues at least through May. The number of young per litter ranges from one to five, averaging about three.

This species is not important economically. On rangelands, the rats may do some damage by consuming seeds of grasses but, in general, losses attributable to them are negligible.

Photo credit: R.D. Porter.