Some animals "hibernate" for part or all of the winter. This is a special, very deep sleep. the animal's body temperature drops, and its heartbeat and breathing slow down. it uses very little energy. in the fall, these animals get ready for winter by eating extra food and storing it as body fat. they use this fat for energy while hibernating. Some also store food like nuts or acorns to eat later in the winter. Bears, skunks, chipmunks, and some bats hiberate.