Like most animals, squirrels are nocturnal and sleep during the night. They are crepuscular which means that they are active for a few hours in the morning and late afternoon, but most of their sleep is done during the dark of night. On average, they sleep for about 15 hours a day or 62% of their total day.
Squirrels that live in forests usually build a nest of sticks, twigs, and branches to sleep in. They are also known to use tree cavities or holes for sleeping purposes. Tree squirrels usually build their nests on a fork of a tree branch that is high enough to protect them from predators.
In winter, gray and red squirrels build a cozy nest called drey to keep warm and sheltered. The foundation of the drey is made from woven twigs and moss. The drey is then lined with soft grass, leaves, and fur to provide warmth and comfort.
Ground squirrels, on the other hand, prefer to sleep in a burrow that they dig into the ground. They typically make their underground dens in autumn for the winter season. They can sometimes be seen sharing the same den with other squirrels for warmth.
The young of both the gray and red squirrels sleep huddled together in a drey after birth. They are deaf and blind when born, so they spend weeks huddled in the drey for protection and warmth until they can open their eyes and start to learn. Ground squirrels in cold climates hibernate through the winter while those living in warmer areas can be found estivating throughout the summer to escape the extreme heat.