California
Sciurus griseus  Alden M. Johnson, California Academy of Sciences | |
| Type of Animal: | Mammals |
|---|---|
| Class: | Mammalia |
| Order: | Rodentia |
| Family: | Sciuridae |
| Federal Status: | |
| State Status: | |
| Occurrence: | |
| Habitat: | Woodland |
| Description: | Western gray squirrels are the largest native tree squirrels in the west. These critters typically occur in oak-conifer woodlands from California up to Washington. The range was expanded as people started planting more oak and walnut trees, but recently their range has been decreasing. The populations are becoming smaller and fragmented as urban sprawl and other developments destroy their habitat. In addition, introduced species are taking over prime habitat. Western gray squirrels are active throughout the day, with morning being the period of greatest activity. They are very wary of humans and prefer to travel by moving from tree to tree. During the winter they live in tree cavities, but during the summer they may live in a nest built from twigs. The nest is also used for the young. Cavities and nests are usually located at least 20 feet above the ground. Cavities are used mainly for sleeping. Western gray squirrels use multiple nests and cavities each day, and they often share with other western gray squirrels. However, there is usually only one squirrel in a nest at a time. Although these squirrels spend a good amount of time in trees, they prefer to forage on the ground. They like to eat fungi, acorns, nuts, seeds, green vegetation, and insects. They often hide acorns under the ground in various locations for later use. They relocate the acorns by scent. The breeding season lasts from December to July, with one peak in the spring and another peak in the summer. Females can potentially have two litters per year, although many have only one litter in some years. Litter sizes range from two to five young, born approximately six weeks after conception. The young first emerge from the nest in May. In the wild western gray squirrels have been observed to live up to ten years. Common predators include raptors, owls, bobcats, coyotes, mountain lions, and martens. Many individuals are also killed as a result of being hit by a vehicle. Two introduced species, the eastern fox squirrel and the eastern gray squirrel, also play a large role in the decline of the western gray squirrel population. The introduced species are more tolerant of humans and therefore have more access to food. With abundance in food, these species can put more energy toward reproduction, so they often have two litters per year. They are also more aggressive than western gray squirrels, so as their populations increase they easily run the native squirrels out of their habitat. In the state of Washington western gray squirrels are classified as threatened, and in Oregon they are classified as sensitive. The California population is currently stable, but the introduced species have had a negative impact. |
| Effort: | |
| References: | Jameson et al. 1988. California Mammals. Wilson et al. (editors). 1999. The Smithsonian Book of North American Mammals. Whitaker (editor). 1998. National Audubon Society Field Guide to North American Mammals, Revised Edition. Zeiner et al. (editors). 1990. California’s Wildlife, Volume III, Mammals. |
| Other Sites: | |
| Field Office(s): | Bakersfield; Barstow; Eagle Lake; Folsom; Palm Springs; Redding; Ridgecrest; Ukiah |