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Western Gray Squirrel Ecology


Western gray squirrels are the largest tree squirrel native to the Pacific Northwest


Current distribution of the western gray squirrel in Washington, 1) South Puget Trough, 2) Klickitat County, and 3) Chelan/Okanogan Counties


Juvenile western gray squirrels (8 weeks old) outside their natal oak den, Klickitat County


The western gray squirrel (Sciurus griseus) is the largest tree squirrel native to the Pacific Northwest. Once common in suitable habitat on both sides of the Cascade Mountains, western gray squirrels in Washington have declined over the last century and their range has diminished. Distribution of western gray squirrels in Washington currently is limited to only 3 locations: south Puget Trough, the North Cascades (Chelan and Okanogan Counties), and south-central Washington (primarily Klickitat County).

Throughout their range, western gray squirrels are most frequently associated with pine trees (Pinus spp.) that provide nesting cover and seeds food, and oak trees (Quercus spp.) that provide natal den sites and acorns for food. In Washington, they also use stands of Douglas fir trees when a component of oak or pine is present. Western gray squirrels require mature stands of trees with sufficient canopy cover to allow arboreal travel and provide secure nest sites, and sufficient complexity of vegetation to provide a multitude of food resources. The amount of suitable habitat available to western gray squirrels has declined substantially as a result of urban/suburban development, conversion of oak woodlands to softwood stands through fire suppression, and changes in forest composition and structure resulting from commercial forestry practices. Additional threats to western gray squirrels in Washington include fragmentation of oak woodlands, invasion of oak-woodlands by non-native plants like Scot's broom, diseases such as mange, and potential competitors such as the introduced eastern gray squirrel (S. carolinensis).

While once hunted in Washington, the western gray squirrel has been protected since 1944 and was listed as threatened by the Washington Department of Fish and Wildlife in 1993. A species Recovery Plan was complete in 2008.

WDFW began studying the ecology of this threatened species in the late 1990s and has ongoing or completed projects in each of the 3 extant populations.