Hibernation is Suspended Animation

A hazel dormouse or common dormouse (Muscardinus avellanarius) during hibernation
A hazel dormouse or common dormouse (Muscardinus avellanarius) during hibernation found in a bird box (central Germany).Zoë Helene Kindermann, CC BY-SA 4, Wikimedia Commons

Hibernation is how many animals spend the winter.

During the cold winter months it is quiet outdoors. Most of the summer birds have flown south to warmer climates. Frogs, turtles and bears have disappeared. Both warm and cold-blooded animals retreat to burrows, dens and winter shelter.

There are many animals which pass the cold months in a sort of suspended animation. This suspended animation is commonly called “hibernation”.

The more I learn about hibernation the more I realized it is a continuum of behavior. A sliding scale seems to exist of how deeply animals hibernate and when. Some animals hibernate deeply for days, weeks or months. Some animals hibernate in winter and others during the hot, dry days of summer.

Here we will focus on hibernation in winter.

Hibernation in Winter

Hibernating during the winter helps the animal to survive cold weather when food is scarce. Hibernation describes “deep hibernators” such as chipmunks and groundhogs.

Body Changes

Hibernating animals spend relatively little time asleep. During hibernation, an animal lowers its’ metabolic rate and need for energy. The heart rate and breathing slows down greatly.  The body temperature drops to nearly that of the surrounding air.

This suspended state also protects the animal from the cold and reduces the need for food. During this suspended state, the animal’s body doesn’t need energy for growth. Growing stops during hibernation. But, the body does need energy for maintenance and to stay alive.

Staying Alive

Since the metabolism has slowed down, little energy is needed for body functions.

Most warm-blooded animals that hibernate eat large quantities of food in the fall. Fat is stored food. Energy from stored body fat is enough to keep the body functions going.

This energy from stored fat keeps the heart pumping , the lungs breathing and other body functions working.  This is why animals such as groundhogs and bears eat so much and grow so fat before winter sets in. An animal enters hibernation in the autumn very fat. It emerges in spring much thinner. All that stored body fat produces energy to stay alive.

Little Brown Bats (Myotis lucifugus) hibernating
Little Brown Bats (Myotis lucifugus) hibernating

Cold blooded animals are unable to produce any significant amount of heat in winter. Their body temperatures rise and fall with the temperature of the surrounding environment. The falling temperatures of autumn cause these animals’ bodies to go into hibernation. These animals bodies fill with an anti-freeze like substance. Cold-blooded animals will leave hibernation when their body temperatures rise enough to heat up its body.

How Do They Do it

Researchers still don’t understand how natural hibernators put themselves into hibernation or how they bring themselves out of it.

From experiments there maybe a biochemical basis that triggers this suspended state. Experiments done on the blood of hibernating animals shows at least one of the triggers is present in the blood.

How This Can Help Humans

Scientists have noted that when an animal’s body approaches the freezing point, they bleed very little and feel little pain. This knowledge is used during surgery. Surgeons chill the body by packing in ice to lower the body temperature. This reduces the need for replacement blood. The need for aesthetics is also reduced.

Being able to hibernate would also help in space travel. Astronauts could be placed in a state of suspended animation for long space voyages. They would need little energy to stay alive. And during long months of space travel not need food or water. They could wake up toward the end of a long journey.

Who are the Hibernators?

Ground squirrels, woodchucks, bats, snakes, turtles and frogs. Bears hibernate but are light sleepers. See Bears Hibernate In Their Own Way

Autumn in the Natural World by Donna L. Long

Learn how plants and animals prepare for winter’s cold. Available in pdf and paperback.


Related Posts

Bears Hibernate In Their Own Way

A Chipmunk’s Winter Sleep (Torpor and Hibernation)

How Can Moose Stand in Snow and Their Feet Not Freeze?

How Cold-Blooded Frogs Survive the Winter and Emerge in Spring


Works Consulted

“Hibernation”, by R. Baird Shuman. Magill’s Encyclopedia of Science: Animal Life (2002), vol. 12, p. 761-764.

“Perchance to Hibernate”, by Ben Harder in Science News, January 27,2007, vol. 171, p. 56-58.


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