The San Joaquin antelope squirrel, also called the Nelson's Antelope squirrel, inhabits the San Joaquin valley of central California. It is a relatively small ground squirrel, about 8.5-9.5 inches in length, with small ears, short legs and a short tail. The upper part of the body is buff or tan, with a white stripe running down each side. Because of the small size and the stripes, this squirrel is often mistaken for a chipmunk, but unlike chipmunks the San Joaquin antelope squirrel lacks black and white stripes on the face and back.
San Joaquin antelope squirrels are omnivorous. Their prefered foods include vegetation, fungi, seeds, and insects, especially grasshoppers. Green vegetation makes up most of their diet from December through April, when this food is most abundant. During the remainder of the year insects may make up 90 percent of the squirrels' diet. Vegetation and insects are prefered over seeds, probably because they provide greater amounts of water, which is vital in an arid climate. They are diurnal, or active during the day, and usually forage for food in the early morning and the evening, especially in the summer when they will retreat to their burrows during the hottest part of the day. These squirrels are not tolerant of extreme heat, but do very well in colder weather and do not hibernate during the winter.
San Joaquin antelope squirrels live in small groups of about 6-8 individuals. They either dig their own burrows or, perhaps more often, use abandoned burrows of kangaroo rats. They breed once each year, with the births taking place in March or April. Young first leave the nest about 30 days after birth.
Sadly, the San Joaquin antelope squirrel is an endangered species. Its range has been reduced by about 80 percent by agriculture, petroleum development and urban sprawl. In addition, the use of pesticides in commercial agriculture may be reducing the supply of insects, one of the squirrels' most important foods. And some of their most important vegetable foods are being displaced by invasive plant species. Currently the species survives only in two areas of the San Joaquin valley. One of these areas, the Carrizo Natural Area, is protected public land. Nevertheless, this small ground squirrel faces a precarious future unless strong steps are taken to protect and expand its remaining habitat.