AppearanceThe 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.
Compared with the Eastern Gray Squirrel ''S. carolinensis'' or the Eastern Fox Squirrel , these squirrels are shy, and will generally run up a tree and give a hoarse barking call when disturbed. Weights vary from about 0.4 to 1 kilogram , and length from 45 to 60 centimetres . It is the largest native tree squirrel in the western coastal United States. 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 molt in the fall. Tail hair is replaced only in the spring. Nesting mothers will use their tail hair to line birthing nests. Western Gray Squirrels eat berries, nuts, a variety of seeds, and the eggs of small birds.
ReproductionWestern Gray Squirrels mate over an extended period ranging from December through June. Young are born after approximate 44 day gestation period. Juveniles emerge from nests between March and mid-August. Litter sizes range from one to five kits which remain in the nest for a longer period than other squirrels. The kits are relatively slow in development, and will not leave the nest for six months or more - another species disadvantage when in competition with other, more-rapidly fledging squirrels. Young gray squirrels have furled tails which will not reach fullness until adulthood. This is a good indicator of age and maturity. Mother squirrels often seem to be overworked with a stressed appearance, 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.
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