Many people believe that all squirrels hibernate during the winter because they are seldom seen. Ground squirrels hibernate during the winter, but tree squirrels, such as the common eastern gray squirrel, do not.
Squirrels spend their entire lives in an area of just three to five acres. They spend their winters living in the same places where they live during the warmer months.
In the fall, squirrels are busy caching, or hoarding, food for the winter. They usually put their food in shallow holes and cover it and sometimes hide nuts in trees. It is estimated that a squirrel will bury enough food every summer and fall to last three years. Squirrels generally eat a vegetarian diet, but in times when food is very scarce they have been known to eat small birds and eggs.
Squirrels do not always remember the locations of all of those storage areas. They will eat the food that they remember during the winter, and seeds that they leave behind will sometimes germinate and grow into shrubs and trees.
Squirrels also eat more in the fall to put on additional fat. Gray squirrels cannot maintain a high level of body fat, unlike other animals, so they must also have a store of food available to get them through the winter.
Gray squirrels are homeotherms, mammals that keep their body temperatures relatively constant throughout the year and do not hibernate. Squirrels can be territorial, but during the winter they huddle together to stay warm in their dens, or dreys. Squirrels also keep warm in the winter by shivering.
Squirrels are sometimes active during the winter but will stay inside their dens during bad weather. When the weather warms up, squirrels emerge from their dreys to begin hunting for food again.