Most squirrel species live in either dens or dreys. A den is a nest inside a tree cavity, while a drey is generally situated in the crotch of a tree limb and is often at least 20 feet off the ground.
Dreys may be near the main trunk of the tree, in an area where several small branches meet or on a strong, thick limb. Squirrels' nests are constructed of moss and the bark, leaves and twigs of deciduous trees. Grass, pine needles and softer materials are used to line the interior. Dreys are typically abandoned after a year or two, with adults normally keeping more than one in case one of their dreys is disturbed.