||The Mammals of Texas -
Merriam's Kangaroo Rat
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
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
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.