Western gray squirrel

Western gray squirrel sitting on a dead tree trunk in the forest

Western gray squirrel

Latin name
Sciurus griseus
Category
Mammals
State status
Threatened

Legal status

Western gray squirrels are a protected species in Washington and cannot be hunted, trapped, or killed (WAC 220-200-100).

Nest sites

All tree squirrels contrast nursery nests in hollow trees, abandoned woodpecker cavities, and similar hollows. Where these are unavailable, they will build spherical or cup-shaped nests in trees, attics, and nest boxes. Western gray squirrel nests are large and often clustered in dry oak / conifer forests. Occupied nests may have fresh leaves, green conifer boughs, or lichen on top.

Food and feeding habits

Tree squirrels feed mostly on plant material, including seeds, nuts, acorns, tree buds, berries, leaves, and twigs. However, squirrels are opportunists and also eat fungi, insects, and occasionally birds’ eggs and nestlings.

Squirrels store food and recover it as needed. Hollow trees, stumps, and abandoned animal burrows are used as storage sites. Flower pots, exhaust pipes, and abandoned cars are also used.

Reproduction

Western gray squirrels mate from early winter to late spring, with one litter of two to four young appearing from March to June. After about 30 days of age, the young are fully furred and make short trips out of the nest. At about 60 days of age, they eat solid foods and venture to the ground.

At about three months of age, juvenile squirrels are on their own, sometimes remaining close to the nest until their parents’ next breeding period.

Mortality and longevity

In trees, squirrels are relatively safe, except for the occasional owl or goshawk. On the ground, large hawks and owls, domestic cats and dogs, coyotes, and bobcats catch squirrels.

Vehicles, disease, and starvation also kill squirrels.

Most squirrels die during their first year. If they can survive the first year, they typically live three to five years.

Description and Range

Physical description

The western gray squirrel is the largest tree squirrel native to the Pacific Northwest. They are steel gray on the back, with contrasting white on the belly and throat, resulting in the name, "silver gray squirrel" in some parts of their range.

They are distinguished by their very long and bushy tails that are primarily gray with white-frosted outer edges. They also have prominent ears, which can be reddish-brown on the back in winter. This occasional small patch of brown is only visible upon close inspection and is the only part of the squirrel that may have any brown.

The western gray squirrel's large size, bushy tail, and gray fur lacking any brown on the body or tail are keys to distinguishing it from other tree squirrels in Washington.

Geographic range

The western gray squirrel was added to Washington’s list of state threatened species in 1993 when surveys indicated a decline in its geographical distribution. The species was once common at low to mid-elevations in dry forests where oak, pine, and Douglas fir mix. It could be found in the south Puget Trough and Columbia River Gorge and on the east slope of the Cascades north to Okanogan County.

It's range is now limited to three isolated populations: the oak woodlands and conifer forests of Klickitat and southern Yakima counties; low to mid-elevation conifer forests in Okanogan and Chelan counties; and the oak woodlands and conifer forests on Joint Base Lewis-McChord in Pierce and Thurston counties. The North Cascades population is the only one occurring outside of the range of Oregon white oak in Washington.

Throughout their range, western gray squirrels are most frequently associated with pine trees, which provide nesting cover and seeds for food, and oak trees, which 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 provide secure nest sites and allow for traveling about in trees. They also need a diverse selection 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 to forest composition and structure as a result of 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.

 

The Washington Department of Fish and Wildlife maintains records on the distribution of western gray squirrels in Washington. The public’s assistance in reporting sightings of this species is appreciated.