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  The Mammals of Texas - Online Edition

Rock Squirrel
Order Rodentia : Family Sciuridae : Spermophilus variegatus (Erxleben)

Rock Squirrel (Spermophilus variegatus).  Photo courtesy of Texas Parks and Wildlife.Description. A large, moderately bushy-tailed ground squirrel; upperparts mottled grayish brown, the hind back and rump more brownish (head or head and upper back blackish in some parts of the state); tail mixed buff and brown, edged with white; underparts buffy white or pinkish buff. External measurements average: total length, 468 mm; tail, 210 mm; hind foot, 57 mm. Weight of adults, 600-800 g.

Species distribution mapDistribution in Texas. Known from the Trans-Pecos and central regions of the state.

Habits. Rock squirrels are nearly always found in rocky areas — cliffs, canyon walls, talus slopes, boulder piles, fills along highways, and so forth — where they seek refuge and have their dens. In the Pecos River Canyon in western Texas, where the walls are a series of alternating, nearly vertical precipices and narrow horizontal shelves, these squirrels are very much at home. They scale the steep, smooth walls with speed and assurance and never hesitate at what appear at a distance to be perfectly smooth surfaces. Closer inspection usually reveals that cracks and fissures in the rocks offer them adequate footing.

Although typical ground squirrels in most respects, they can climb trees nearly as well as tree squirrels. In the Guadalupe Mountains of western Texas, they have been observed 5 or 6 m up in the flowering stalks of agaves feeding on the flowers and buds. They also climb to the tops of junipers to forage on the berries and in mesquites to feed on the buds or beans. Occasionally, they den in tree hollows 5 or 6 m from the ground. The usual den, however, is a burrow dug under a rock; others are in crevices in rock masonry along railroads and highways, cavities in piles of boulders, or small caves and crevices in rocky outcrops. They are diurnal and most active in early morning and late afternoon, but they are rather shy and difficult to observe at close range. Their call is usually a repeated sharp, clear whistle.

They feed on a variety of plant materials depending on availability. Known items include acorns, pine nuts, walnuts, seeds of mesquite, cactus, saltbush, agave, wild gourd, cherries, sumac, spurge, serviceberry, berries of currant and juniper, and all sorts of cultivated fruits and vegetables. Insects also contribute importantly to their diet, especially grasshoppers, crickets, and caterpillars. They are fond of flesh and are known to catch and eat small wild turkeys and other birds.

They store quantities of food for winter use which, coupled with the fact that they are seen occasionally in winter on mild days, suggests that they either do not hibernate or that hibernation is incomplete and only for short periods. At lower elevations in the Big Bend region of Texas they are active all year.

Mating activities begin in March and continue into July, which suggests that two litters may be produced each year. Litter size ranges from two to five. Gravid females have been collected in June. Young squirrels first appear above ground at 6-8 weeks of age, and young about quarter-grown have been captured as early as June and as late as September 20. Little is known about the birth and early life of the young squirrels.

Photo courtesy of Texas Parks and Wildlife.