Spotted Ground Squirrel
Order Rodentia : Family Sciuridae : Spermophilus spilosoma Bennett

Description. A small ground squirrel with scattered, more or less squarish, light spots on back (spots not in rows as in S. mexicana and S. tridecemlineatus); ears inconspicuous; tail about one-third of total length, pinkish buff or cinnamon buff beneath; upperparts smoke gray, light drab or fawn color, the white spots small and obsolete, especially on shoulder; underparts white. External measurements average: total length, 214 mm; tail, 65 mm; hind foot, 32 mm. Weight, 100-125 g.

Distribution in Texas. Known from western one-half of state (not on Edwards Plateau) and southward on Rio Grande Plain.

Habits. Spotted ground squirrels seem to prefer dry, sandy areas, but they are also found in grassy parks, open pine forests, scattered brush, and occasionally on rocky mesas. On Mustang Island, off the coast of Texas, they live in the sand dunes and share their runways through the sparse vegetation with kangaroo rats, grasshopper mice, and other small rodents. Near Van Horn, they are rather common in the sandhills covered with yuccas and other desert shrubs, and in the southern part of the Big Bend they occur in small numbers on rather hard ground covered with creosote bushes. The opening to their burrows is usually under bushes or overhanging rocks. One excavated burrow had three openings, was about 4 m long, descended no more than 50 cm, and terminated in a nest chamber. A burrow in the Big Bend had an opening about 5 cm in diameter and was marked by a slight mound.

These squirrels are extremely shy. One can work in an area several days without seeing them. They are most active in early morning and late afternoon to avoid the midday heat. They seldom go far from their burrows and retreat to them at the slightest sign of danger. Their movements are rapid and interrupted by abrupt stops, reminding one of a lizard. In running, the body and tail are held close to the ground.

Hibernation probably is not complete in these squirrels, especially in the southern part of their range. Specimens have been taken in November, December, January, and February in Texas.

Their food is largely green vegetation and seeds. Specific items are cactus pulp, mesquite beans, saltbush seeds, sandbur, sunflower, gourd, iris, grasshoppers, and beetles.

Their breeding habits are not well-known. Females captured in mid-June, at which time half-grown young were common, contained five to seven embryos. This indicates that two litters may be reared yearly. Young, presumably about a month old, have been observed above ground as early as April 28 and as late as September 17, which would suggest that mating begins in February and continues into mid-July. The gestation period is not known, but is probably about 30 days. Six young spotted ground squirrels reared in captivity were found to weigh an average of 17 g at 34 days of age, their eyes opened at 27-28 days, and they were weaned at about 48 days.

Photo credit: R. D. Porter.