Ammospermophilus interpres
Texas antelope squirrel

Ammospermophilius interpres occurs on the Chihuahauan plateau of the southwestern United States (Best, 1999), mainly Texas and New Mexico, and in north-central Mexico. It is distinct from A. leucurus, which lives in Oregon, California, and New Mexico (Walker, 1983; Davis, 1960; LTER; Best, 1999).

A. interpres are characteristic of sparsely vegetated areas. They seems to prefer lowland areas like valleys or low hills and have been seen perched on boulders or short junipers. They are seen primarily in rocky areas and less often in flat sandy areas (Walker, 1983; Davis, 1960; Best, 1999). They dig multi-chambered dens, and they use rock crevices and abandoned dens of other animals as their dens. They normally locate these dens in a cut bank or at the base of a large object such as a bush or a rock. Often the den has more than one entrance. The nest inside the den is lined with bits of fir and feathers, dried grass, and any other soft material the squirrel finds (Davis, 1960; Best, 1999). Canyons and rocks seem to be important in determining their range (Best, 1999).

A. interpres average 226 mm in length with males weighing between 94 and 121 g. and females between 84 and 115 g (Davis, 1960; Best 1999). The coat is course in texture with light gray-brown to red brown coloring and a white stripe on each side extending from the shoulder to the base of the tail. The stripes are surrounded by darker portions of the main coat color. The eyes are outlined by white fur. The legs have reddish fur (Best, 1999). The tail has three black bands on the dorsal side. Near the body it is black, but the distal two thirds is grey (Best, 1999). The under parts including the tail are white in the summer and gray in the winter. A. interpres generally holds its tail over its back, exposing the contrasting white ventral fur. It has small external ears and ten mammae (Walker, 1983; Davis, 1960; LTER; Best, 1999).

A. interpres is strongly diurnal, even venturing out in the heat of the day when other animals sleep. When active A. interpres occasionally retreats to a shady place and stretches out on the ground, dispersing its excess body heat in the cool rocks (Davis, 1960). They are extremely nimble, and spend most of their time on the ground, though they have been seen perching on large objects (Walker, 1983; Davis, 1960; Best, 1999). When agitated they flick their tails (Davis, 1960; Best, 1999). They do not hibernate, though individuals in the northern range may become inactive during the winter (Walker, 1983; Davis, 1960).

A. interpres has a largely vegetarian diet consisting of fruit and seeds from various plants, as well as insects. It has been found to collect food using its cheek pouches and store it in the den and under rocks (Davis, 1960; Best, 1999). In the spring individuals eat a large number of succulents and other vegetation (Best, 1999). A study of a related species, A. leucurus found that species to be omnivorous, eating arthropods and some vertebrates, depending on the season (Bradley, 1968). Another study has shown that succulents are important in the diet of A. leucurus, in order to maintain body moisture in the arid climates inhabitated by that species (Hudson, 1962).

Common foods eaten include: yucca, juniper, salt grass, prickly pear fruits, cholla fruits, mesquite, sotol, creosote bush and insects.

In its range A. interpres is so common that it is an important food source for many predators, including humans (Best, 1999).

In some areas A. interpres can become a nuisance by raiding crops, but is controlled by various poisoning methods (Walker, 1983; BISON).

In some cases different species of antelope ground squirrels are being displaced by farms and settlements, which alter their habitat, forcing them to shift their range to non-traditional areas (BISON). Global warming could also be playing a role in the shifting ranges (Cameron, 2001).

Much of the information available about antelope ground squirrels is about a species other than A. interpres. Davis (1960) and Best (1999) were the best sources.