The latin word hibernation means “winter”. Some animals like chipmunks hibernate in the winter do to the lack of food available in the wild. Hibernating animals spend the warm months building  body fat from excessive consumption. When winter arrives they go into a hole to sleep. The heartbeats slower and the breathing and body temperature also drop. The animals do not need much food in this state and their body fat keeps them nourished so they do not have to eat all winter. Many rodents and animals like the gopher, woodchuck and bats hibernate the entire winter. Other animals like the squirrel and the bear go into winter homes when winter arrives. They are not really hibernating, they sleep much of the winter but come out occasionally to eat.