California Ground Squirrel

The California Ground Squirrel, Spermophilus beecheyi (referred to in some older sources as Otospermophilus beecheyi or Citellus beecheyi), is a common and easily observed ground squirrel of the western United States and the Baja California peninsula; it is common in Oregon and California and its range has relatively recently extended into Washington.

The squirrel's upperparts are mottled, the fur containing a mixture of gray, light brown and dusky hairs; the underside is lighter, buff or grayish yellow. The fur around the eyes is whitish, while that around the ears is black. Head and body are about 30 cm long and the tail an additional 15 cm. The tail is relatively bushy for a ground squirrel, and at a quick glance the squirrel might be mistaken for a Fox Squirrel.

As is typical for ground squirrels, California Ground Squirrels live in burrows which they excavate themselves. Some burrows are occupied communally. Although they readily become tame in areas used by humans, and quickly learn to take food left or offered by picnickers, they spend most of their time within 25 m of their burrow, and rarely go further than 50 m from it.

California Ground Squirrels are frequently preyed on by rattlesnakes. They are also preyed on by eagles, raccoons, red foxes, badgers, and weasels. Interdisciplinary research at the University of California, Davis since the 1970s has shown that the squirrels use a variety of techniques to reduce rattlesnake predation. Some populations of California Ground Squirrels have varying levels of immunity to rattlesnake venom as adults. Female squirrels with pups also chew on the skins shed by rattlesnakes and then lick themselves and their pups (who are never immune to venom before one month of age) to disguise their scent. Sand-kicking and other forms of harassment provoke the snake to rattle its tail, which allows a squirrel to assess the size and friskiness (dependent on blood temperature) of the snake.

Another strategy is for a squirrel to super-heat and swish around its tail. When hunting, rattlesnakes primarily rely on their pit organ, which detects infra-red. The hot-tail-swishing appears to convey the message "I am not a threat, but I am too big and swift-moving for it to be worth trying to hunt me." These two confrontational techniques also distract the snake from any nearby squirrel burrows containing pups.

In the colder parts of their range, California Ground Squirrels hibernate for several months, but where winters are mild some squirrels are active year round. In those parts where the summers are hot they may also estivate for periods of a few days.

California Ground Squirrels are often regarded as a pest in gardens and parks, since they will feed off ornamental plants and trees.