The list of animals that hibernate is extensive and not all animals on the list always hibernate. Animals most likely to hibernate are those that live in areas with extremely cold winters, and degrees of hibernation may vary. The typical bear that hibernates doesn’t do so in the same manner as a ground squirrel for instance. Degree of wakefulness of animals in this state can change. Further, climate changes and a warming earth can have an adverse affect on hibernating animals. If the weather warms earlier than what is typical, animals may come out of hibernation, but still not feed, causing near starvation and sometimes death.

There are examples of both warm and cold-blooded hibernating animals. Even a few fish, amphibian and insect species survive winters through this process. Additionally some animals go through what is called estivation. Their bodies slow down during extremely hot weather so they can keep cool. Most animals that estivate are cold-blooded, and depend upon exterior temperature to keep cool. Reducing metabolism, and perhaps hiding under several layers of soil can make extremely hot conditions survivable.

A list of hibernating animals might include the following mammals: Chipmunks, ground squirrels, echidnas, possums, hedgehogs, hamsters, skunks, bats, prairie dogs, marmots, badgers, and some lemurs.

Bears only make the list for some scientists, since they do wake up more frequently during hibernation, and though their metabolism slows during winter, it doesn’t slow to nearly the same degree as most other hibernating animals. Further, many bears give birth during winter, requiring a degree of alertness to care for new cubs. Some scientists prefer to call this denning instead of hibernation. Bears may also fully wake during winter denning and may actually attack people.

Among non-mammals, you can find species of lizards, frogs, toads, newts, snakes, turtles, and insects like bees that hibernate. One bird, the Western Poor-Will is considered a hibernating bird. Other birds, like hummingbirds, may go into a state called torpor on a daily basis. Their metabolism slows at night so they can rest and not require food to stay alive.

There’s some speculation about whether primates could hibernate. Only a few lemurs are known to actually hibernate on a yearly basis. Yet there have been some interesting cases of people surviving exceptionally cold temperatures by falling asleep, where their bodies have gone into the low metabolism state of hibernation. Since these cases are rare, it wouldn’t be a good idea to try this out. In any event, most humans have access to food sources year round and to clothing and shelter, which means hibernation isn’t necessary.