Gray squirrels are tree-dwelling members of the rodent family of mammals. Both Eastern and Western gray squirrels build nests for sleeping. Adults may rotate between as many as three nests, depending on the population density where they live. These nests are usually occupied either by a single adult squirrel or by a mother and her young. Eastern gray squirrels breed twice a year, in the summer and winter, while Western gray squirrels have a single summer breeding season.
Squirrels live in forests throughout the United States and Canada, preferring stands of hardwood trees with a moderately dense understory of vegetation. These trees provide gray squirrels with acorns, hickory nuts and beechnuts, which make up the bulk of their diet. Western gray squirrels also inhabit conifer forests, where they feed on pinecones. Both subspecies maintain home ranges of between one and eight acres that often overlap with the home ranges of other gray squirrels.
Both male and female gray squirrels of all ages participate in building dens. They typically build leaf nests in the summer by weaving together small branches they’ve gnawed off of trees. These nests are lined with grass, moss, leaves and pine needles. If the nest is disturbed by predators or becomes infested with fleas or mites, the squirrel moves on to a different location and builds a new nest. Adult squirrels typically can build a nest in one day.
Gray squirrels use leaf nests, also known as “dreys,” primarily during the summer months. They build these nests up to 30 feet off the ground in the fork between a tree limb and the tree’s main trunk, well hidden by the summer foliage. The single entrance is concealed, facing the trunk of the tree. These nests are typically intended for one squirrel, but occasionally two Eastern gray squirrels will sleep together in the same leaf nest if the temperature drops. Squirrels use these nests as temporary shelters, and most adults have more than one in case of insect infestation.
Squirrels also nest in more stable and protected dens in hollow tree trunks. Tree dens are used year-round, but are particularly necessary in winter. An adult typically has at least two different tree dens within its home range. While a female Eastern gray squirrel who mated in the summer may return to the tree den where her winter litter was born, it’s more typical for her to find a new location for each litter. Litters born in tree dens are much more likely to survive than those born in leaf nests.
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