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Last updated on April 16, 2014 at 17:34 EDT

Western Gray Squirrel

The Western Gray Squirrel, Sciurus griseus, is a tree squirrel found along the western coast of the United States and Canada. This species has been known as the Silver-gray squirrel, the California Gray Squirrel, the Oregon Gray Squirrel, the Columbian Gray Squirrel, the Banner-tail, and also simply as the Gray Squirrel. Three geographical subspecies are known. The Western Gray Squirrel was first described by George Ord in 1818 based on notes taken by Lewis and Clark at The Dalles in Wasco County, Oregon.

The western gray squirrel is shy, and will generally run up a tree and give a hoarse barking call when disturbed. They weigh from 14 to 35 ounces, and are from 17.5 to 23.5 inches long, including the tail. Western Gray Squirrels exhibit a form of coloration known as counter shading. The dorsal fur is a silver, gunmetal gray, with pure white on the underside. There may be black flecks in the tail. Ears are large but without tufts. The ears turn reddish-brown at the back in the winter. The tail is long and typically very bushy. Tree squirrels undergo a complete head-to-tail molt in the spring and a rump-to-head mold in the fall. Tail hair is replaced only in the spring.

Western gray squirrels mate from December through June and young are born after about a 44 day gestation period. Juveniles emerge from nests between March and mid-August. Litter sizes range from 1 to 5. Kits remain in the nest for a longer period that other squirrels, and are relatively slow in development. Young gray squirrels will not leave the nest until 6 months or more. Mother squirrels often have a harassed, overworked look, complete with bruised and battered nipples. Mating squirrels can be very sadistic and will bite and injure each other. Females can be quite territorial, and will chase others away and have fairly violent altercations between themselves.

They are strictly diurnal, and feed mainly on seeds and nuts, particularly pine seeds and acorns, though they will also take berries, fungus and other soft food. Pine nuts and acorns are considered critical foods because they are very high in oil and moderately high in carbohydrates, which help increase the development of body fat. They feed mostly in trees and on the ground. They generally forage in the morning and late afternoon for acorns, pine nuts, new tree buds, and fruits.

When on alert, they will spread their tails lavishly creating an umbrella effect that shields them and possibly provides cover from overhead predators. They are scatter-hoarders making numerous caches of food when it is abundant, and thus contribute to the seed dispersion of their food trees. Although they show relatively good scent relocation abilities, some food caches will never be reclaimed, becoming seedlings in the spring. They do not hibernate, but become less active during the winter. Like many prey animals, they depend on auditory alerts from other squirrels or birds to determine safety. Once an alarm call is transmitted, those present will join in, and the trees become a cacophony of barking squirrels. Tree squirrels are prey for bobcats, hawks, eagles, and mountain lions.

Western Gray Squirrel