The San Joaquin antelope squirrel or Nelson's antelope squirrel is a species of antelope squirrel, in the San Joaquin Valley of the U.S. state of California. These squirrels are dull yellowish-brown or buffy-clay in color on upper body and outer surfaces of the legs. They have a white belly and a white streak down each side of their body. The underside of their tail is a buffy white with black edges.
San Joaquin antelope squirrels are found in the San Joaquin Valley, California, USA. They inhabit slopes and ridge tops along the western edge of the valley. Most of today's remaining San Joaquin antelope squirrels can be found in the Carrizo Plain. The squirrels live on sandy, easily excavated grasslands in isolated locations in San Luis Obispo and Kern Counties.
San Joaquin antelope squirrels are social animals. They live in colonies that have about six or eight individuals. These animals prefer deep, rich soil types as they are easy to dig through in both winter and summer temperatures. Although these squirrels may dig for food, they do not make their own burrows and claim abandoned kangaroo rats' burrows as their own. They are diurnal creatures foraging in the morning and evening, and avoid the midday heat. Around noon the squirrels hide in their burrows and are not seen again until about 2 pm. These squirrels like to stretch out and roll over in the dust on the ground. They don't hibernate. San Joaquin antelope squirrels are cautious animals, especially when emerging from their burrows. To help prevent predation, they produce alarm calls. These alarm calls are not loud but associated with convulsive body movements.
San Joaquin antelope squirrels are polygynandrous (promiscuous) which means that both, females and males mate with multiple partners. The breeding season takes place in late winter to early spring and most young are born in March. Females give birth to 6-11 young after the gestation period that lasts around 26 days. The young emerge from their dens in 30 days after birth. Weaning may start or be completed even before the young emerge. During the weaning period, the mother feeds alone and ignores any attempt of her offspring trying to nurse from her. She can sometimes spend the night in a different den if necessary. Once above ground, pups are able to forage for food independently. By early to mid-May the young squirrels have their juvenile pelage and begin to show the changes into adult pelage.
San Joaquin antelope squirrels suffer from increasing agriculture and urban development. An increase in agricultural land is taking away their habitat and leaving them with no alternative. Grazing livestock further destroys what habitat may be left, and exotic plants are able to take over native grasses that these squirrels forage upon and rely on for shade and cover. Another threat comes from pesticide drift from nearby agricultural fields captures the existing squirrel habitat.
The IUCN Red List and other sources do not provide the San Joaquin antelope squirrel total population size. Currently, this species is classified as Endangered (EN) on the IUCN Red List and its numbers today are decreasing.