The round-tailed ground squirrel, known scientifically as Xerospermophilus tereticaudus and referred to in Spanish as the “ardillón cola redonda,” lives in the desert of the Southwestern United States and Northwestern Mexico. They are also called ground squirrels because they burrow in loose soil, often under mesquite trees and creosote bushes.
Extremely small and light, round-tailed ground squirrels usually weigh little more than 4 grams (0.1409 ounce). Adults weigh around 125 grams (4.4 ounces), slightly over one quarter pound. All sport long round tails. They have hairy hind feet. The external top sides of their bodies are sandy in color with no fur markings, matching the soil they burrow into. The underside of their bodies are usually a lighter shade. Round-tailed squirrels average eight to 11 inches in length, including a 2.4 inch to 4.4 inch tail.
This species occurs in sandy desert in low, flat areas, commonly in communities dominated by mesquite and creosotebush; it avoids rocky hills. The squirrels nevertheless have a tolerance of a broad range of habitats. They are found in urban areas and parks. Ground squirrels are well-adapted to desert life. They can stay active even on the hottest of days, although they do tend to limit their activity during the heat of the afternoon sun. They live underground in the winter, typically from late August or September until January or February. They go into torpor, but do not hibernate.
They have a semicolonial social structure, and will alert others of impending danger with a high-pitched alarm call. But they will chase away other ground squirrels that get too close to their own burrow. The males are dominant during the breeding season, which lasts from January through to the beginning of March. The females dominate during raising of the young, in the months of March and April.
The gestation period for round-tailed squirrels is 28 days. Five to six pups are typically born in each litter. They reach sexual maturity at 325 days. There is little information on the longevity of these animals, but one wild-born specimen lived to approximately 8.9 years in captivity. These rodents are prey animals for coyotes, badgers, hawks and snakes.
Omnivorous, the bulk of their diet is green vegetation, especially in the summer. They also eat seeds and insects (ants, termites, and grasshoppers). Most of their foods are chosen for high water content because of the shortage of available water in their environment. The average water content of the food they eat is 80 percent.
This species is common to very common, and does not appear to be threatened with extinction because of its numbers and dispersion. For this species, densities vary with stage-of-life-cycle, with reported numbers ranging from a January low of 160 individuals per ten acres to a high of 840 individuals per ten acres in early May when juveniles emerge from burrows. At a less crowded study site, density of a resident summer population averaged 21 individuals per ten acres.
From Wikipedia, Xerospermophilus tereticaudus by T. Lacher, R Timm, R. & S.T. Álvarez-Castañeda, and iucnredlist.org, the website for The International Union for Conservation of Nature