Which Animals Hibernate?

Tricia Christensen
Tricia Christensen

Both warm-blooded and cold-blooded animals hibernate, including some species of chipmunks, hedgehogs, frogs, turtles, and even some fish. The majority of animals that hibernate are found in the northern and extreme southern areas of the globe — the colder climates of the world. The variety is quite extensive and also includes hamsters, opossums, and badgers. Bears, perhaps the most famous of such animals, don't undergo quite as deep a sleep as many other animals, so some scientists don't consider it true hibernation.

The squirrel, a warm blooded animal, hibernates during the winter.
The squirrel, a warm blooded animal, hibernates during the winter.

Warm-Blooded Animals

Many small warm-blooded animals hibernate during the winter, including many rodents like the dormouse, ground squirrel, and woodchuck. These animals are required to hibernate for part of the year, and once this process begins, they are extremely difficult to wake up. The body temperature of a hazel dormouse, for example, drops to just above freezing, and its heart beats only a few times each minute. A few of these animals will wake up periodically to eat, but others stay in this deep sleep for up to six months. Other warm-blooded animals that hibernate include mouse lemurs and mountain pygmy possums.

Some cold blooded animals, such as the bullfrog, hibernate during the winter.
Some cold blooded animals, such as the bullfrog, hibernate during the winter.

Most birds do not truly hibernate, although the common poorwill, a species in the family called nightjars or nighthawks, does. Found in the Southwestern US and Mexico, this bird can spend weeks or months during the winter in an inactive state. Other birds can go into a state known as torpor, during which they slow their metabolism and body temperature, but this usually only lasts for a short period of time, often overnight. In many cases, hibernation is described as long-term torpor.

Turtles often hibernate.
Turtles often hibernate.

Bears are the most commonly identified animals that sleep through the winter months; however, many scientists do not classify the bear as a true hibernator because it doesn't go through the same degree of physiological changes that other hibernating animals do. For example, while a bear's heart rate and breathing slows, its body temperature doesn't fall very much. Along with some bats, bears are also relatively easy to wake up. Most bears deliver their young during the winter, and so the mother bear must become somewhat conscious during the birthing process to properly tend to her cubs.

Some hamsters hibernate.
Some hamsters hibernate.

Cold-Blooded Animals

Insects, reptiles and other species, including some fish, also hibernate. Since they cannot maintain their body temperatures the way that warm-blooded animals do, many cold-blooded animals seek refuge in hollow trees, caves, or underground to protect themselves during the winter. Some wetland creatures — as well as fish — often bury themselves in mud at the bottom of a lake or pond. This not only protects the creature from the elements, it prevents the current from washing the creature downstream and guards it from becoming a meal for other predators that do not hibernate.

Hedgehogs are hibernating animals.
Hedgehogs are hibernating animals.

Some experts draw a distinction between the winter dormancy periods of warm- and cold-blooded animals. Rather than "hibernation," they refer to it as "brumation" when it occurs in reptiles. The main difference is the energy source; mammals eat extra food before hibernating and use the stored fat to get them through the winter, while reptiles survive on glycogen, an energy storage molecule. For practical purposes, however, the two states are very similar.

Some scientists don't consider bears to be true hibernators.
Some scientists don't consider bears to be true hibernators.

How Hibernation Works

Hibernation allows an animal to slow its life support systems tremendously, often having only one heart beat occur over several minutes. This altered metabolism not only saves energy, it prevents the animal's body from requiring additional food and water while it sleeps. The animal's body temperature also drops, and the majority of the warmth is concentrated near and around the vital organs. In some animals, such as the opossum, the young are born while the mother sleeps; the newborns make their way into a pouch on the mother's underbelly, where they nurse throughout the remainder of the mother's hibernation period.

Bats are known to be easily awakened when they go into their winter torpors.
Bats are known to be easily awakened when they go into their winter torpors.

In some instances, the weather can turn unusually warm early in the season, bringing the animals out of their hibernating state much earlier than usual. This can often prove to be life-threatening for the animal, because food, such as grasses and berries, are not yet available. In this case, the animals may become starved and malnourished. Such a season can also be life-threatening to newborns as their mother's milk may dry up due to her lack of nutrition.

Opossums are an example of an animal whose babies are born while the mother sleeps.
Opossums are an example of an animal whose babies are born while the mother sleeps.
Tricia Christensen
Tricia Christensen

Tricia has a Literature degree from Sonoma State University and has been a frequent wiseGEEK contributor for many years. She is especially passionate about reading and writing, although her other interests include medicine, art, film, history, politics, ethics, and religion. Tricia lives in Northern California and is currently working on her first novel.

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Discussion Comments


Yes they do. Butterflies rock.


can butterflies hibernate?


Are butterflies animals?


is their any psychological answer regarding hibernating of animals?


i was wondering the same, anon46191. Can people hibernate? that would be interesting.


why do animals hibernate?


i think animals should not hibernate.


Does every animal hibernate?


do bees hibernate?


Cold-blooded animals always hibernate.


do animals wake up in february?


how does environment affect hibernating animals?


do all animals who hibernate or hibernate in just one place?


We have an animal that collects rocks in the night time and stores them under our barbecue. If we remove the rocks, the next morning about 50 small rocks have been replaced. What animal carries and stores rocks in Henderson, Nevada?


Can box turtles hibernate?


do raccoons hibernate?


i wonder if people can hibernate?


when do animals hibernate?


at what temperature do spiders hibernate nd does scorpions hibernate


of course chimpanzees don't hibernate, they don't need to because they don't live in the cold.


What birds hibernate?


where do these animals live that hibernate? are there any that live in the tropical rainforest?


can yaks hibernate???


Yes, um, can you make a list of ten animals that always, "always" being a keyword, hibernate??? It would really help!


Can chimpanzees hibernate?

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