Adult eastern grey squirrels are about 50 cm (19.5 in.) long, and their bushy tail can make up half that length. This tail is quite useful, serving as a rudder to help the squirrel steer when it jumps, a sun shade or rain cover, a blanket during the winter, and a means of communication.
Despite its name, eastern grey squirrels are highly variable in colour. The typical colouration is a grey back with white underparts and some yellow-brown areas around the head, flanks and under the tail. White animals occur rarely; the most common variety apart from grey is black. The black form is found mainly in northern parts of the range, mostly in eastern Canada; the darker colour may give the animals a thermal advantage (help keep them warmer) during winter.
Although they live in hardwood and mixed forests, eastern grey squirrels are also common in urban spaces like parks and lawns, where its predators are few.
They have a varied diet that includes acorns, hazelnuts, fruit, buds, flowers, bark, maple sap, mushrooms, insects, young birds and eggs. They are classic scatter hoarders: during late summer and autumn they bury or hide small amounts of food all around their home range for use during the cold season. Their frenetic activity during this busy time reduces their vigilance, and many ultimately fall beneath the wheels of motor vehicles.
Eastern grey squirrels live in trees, where they create two types of homes. During the summer, they make a nest of leaves and twigs (called a dray) in the fork of a branch. During the winter, they live in a tree hollow, which provides more protection from the cold.
In Canada, most female eastern grey squirrels have a single litter in April, following a breeding season in late February and early March and a gestation of around 44 days. Most litters contain two to three young. If the weather is favourable and there seems to be enough food, some females will produce a second litter in late July, although it is uncommon in colder parts of Canada.
The distribution of the eastern grey squirrel is not limited to Canada. It is native to eastern North America. They have also been successfully introduced into southwestern British Columbia and into parts of Europe, where they are considered a pest because they displace native species.