The most common tree squirrel in Western Washington is the non-native Eastern Gray Squirrel. Introduced into the Seattle area in the early 1900s, it has become well established in cities and suburbs.
Gray squirrels are active during the day, especially early morning and late afternoon. Gray squirrels build large nests of leaves and twigs on tree branches or within tree cavities. They also nest in buildings where they can gain access through open spaces in the roof, attic or walls.
Although they do not hibernate, squirrels often remain in their nests in cold or stormy weather, venturing out when they need to find food, which they often have cached near their nests.
Eastern Gray Squirrels are omnivorous. They eat seeds, nuts, tree bark and buds, fungi and occasionally eggs and nestling birds. Like other rodents, squirrels are gnawers, using their sharp, constantly growing front teeth to strip bark and chew through wood and plastic.
Breeding season begins in late winter. Depending on conditions and food availability, squirrels may produce two litters a year. Average litter size is three, and the babies are born naked and blind. Young squirrels remain in the nest for about six weeks.
Squirrels are opportunistic, making use of all sources of food and shelter available to them. They can also cause property damage, gnawing through electrical wiring or overturning bird feeders. The best way to discourage squirrels is to change your property to make it unappealing to them.
Squirrels, especially adult females, seek openings for potential den sites, and a house in poor repair is an invitation to move in. Gnawing to enlarge holes, squirrels can enter through small spaces. If you suspect a squirrel is living in a wall or attic, look for likely entries and listen for telltale scampering sounds.
Squirrels will return to a building with loose, holey or rotting siding, boards and shingles. Repair or replacement it is essential to squirrel-proof the building permanently. Also, trim branches away from the sides and roofs of buildings to prevent easy access.
To keep squirrels from stripping bark or otherwise damaging trees, wrap a 24-inch metal cylinder around the trunk at least six feet high, and trim lower branches. Occasionally, squirrels dig up bulbs, which can be protected by laying chicken wire over the soil.
Above: A Douglas Squirrel in the wild