Swapna Krishna

Jun 22nd 2022

What Is Hibernation, and How Do Animals Do It?


We all learn at a young age that during the winter bears go into hibernation. What is hibernation, and how do these animals hibernate and wake up months later? If you think about it, the fact that bears have the ability to put their bodily functions on pause for a few months of the year can seem miraculous.

When humans are in a coma — defined as a prolonged state of unconsciousness — our bodies still function. While the brain experiences minimal activity, the rest of the patient’s bodily functions continue as normal. The patient is fed through a tube, and creates and disposes of waste as normal. They just don’t respond to any external stimuli.

But bears and other animals such as chipmunks, hedgehogs and bats hibernate for months at a time, essentially shutting down their bodies while they do so.

How Do Bears Manage Weight During Hibernation?

The human body comes in all shapes and sizes. Many of the factors leading to size and weight are genetic, and the medical field is finally moving toward ending the shame surrounding obesity. But regardless of size or weight, human bodies weren’t built to gain and lose weight quickly, much less do it multiple times per year.

Bears’ bodies are. A recent study in Communications Biology shows that bears are able to pack on the pounds during their awake period, storing it as fat. Over the course of hibernation, their bodies slowly work through that reserved body fat, which provides the energy needed to maintain their bodies through this long period. Their muscles, however, are untouched and retain the same density throughout hibernation periods.

This is in stark contrast to humans. Our muscles atrophy after not being used for just a few days, as studies of astronauts coming back from space have shown. However, bears’ bodies are built to handle hibernation. They take drastic weight gain and loss well, and they are able to process fat but preserve muscle to keep the bear alive during their periods of hibernation.

Squirrels Drop Their Body Temperature

What is hibernation to other animals? Body temperature regulation is a key to survival for many species. Some even drop their body temperature low enough to no longer require food. According to an article in The Atlantic, squirrels lower their basal body temperature from 99 degrees F to 27 degrees F. This suspends most of the bodily functions of animals that hibernate, allowing them to sleep for months at a time and not generate bodily waste.

Humans, unfortunately, are much more susceptible to temperature changes than hibernating animals, and a difference in body temperature of a few degrees Fahrenheit can have a drastic impact on a person’s health.

Lemurs Rely on Good Insulation

Not unlike a human insulating their home, the fat-tailed dwarf lemur relies on good insulation of its tree hole to survive hibernation. It’s one of the few primates — and few tropical-dwelling animals — to hibernate. During Madagascar’s dry season, these lemurs rely on good insulation of their tree holes to wake up regularly and to sleep.

A common misconception about hibernation is that it’s sleeping, but hibernation and sleep are two different things. Animals that hibernate still need to rouse themselves from sleep, or they will die. Lemurs rely on the environment to regulate their body temperature while they’re in hibernation, and a well-insulated tree hollow means they can maintain a constant body temperature.

Humans may never be able to hibernate, but it’s interesting to look at the similarities and differences between us and hibernating animals to see what we can learn from them.

Are you interested in science and innovation? We are too. Check out Northrop Grumman career opportunities to see how you can participate in this fascinating time of discovery.