As the first snow falls and birds fly south for the winter, it begs to wonder which animals are going into hibernation this time of year. We’ve all heard how bears hibernate, but what exactly does hibernation mean? What about other animals around the world hibernate? What about humans? Do we hibernate when suffering from sleep disorders like narcolepsy? Let’s jump right in and discuss all things hibernation to find the answers to these questions.

How Hibernation Happens

First of all, hibernation is more than just snoozing through the winter season. BBC Wildlife Magazine reports that hibernation is a way for animals to survive cold temperatures. This is a physical phenomenon in which an animal lowers its metabolism and body temperature so they can survive through months of cold weather. For example, during hibernation, a ground squirrel will drop to a body temperature of 28 degrees F. That’s below freezing!

Other animals, like frogs or snakes, have a naturally occurring antifreeze that flows through their system to help avoid freezing—in the same way, our vehicles operate in winter months. In terms of slowing metabolism rates, a bat can lower its heart rate to 11 beats, down from an awe-inspiring 400 bpm when they are in active mode.

Hibernation can be achieved for a month or two, or for half the year, depending on the species and habitat. In order to avoid starving to death during hibernation, animals must store excess body fat that is burned off while in hibernation mode. Another interesting fact: if an animal is woken up while in hibernation, they can die due to the sudden change in body functions.

Animals that Hibernate

We all know that bears hibernate, but actually, not all bears hibernate. Earth Rangers says that only four types of bears actually hibernate: brown bears, polar bears, Asiatic black bears, and the American black bear. By the way, brown bears include grizzly bears, so these too are hibernators.

But what about other types of animals that hide out for the winter months? According to National Geographic, little brown bats hibernate through fall, winter, and spring. Hedgehogs also hibernate in winter, as do yellow jackets, box turtles, and garter snakes. Other interesting animals that hibernate include hummingbirds, snails, and Gila monsters.

Chipmunks hibernate, but since these little rodents have such high metabolisms, they still must snack often while in hibernation. Their cousins the dormouse, Arctic ground squirrel, white-tailed prairie dog, and marmots do the same when they hibernate.

Narcolepsy vs. Hibernation

Do humans hibernate when suffering from sleep disorders like narcolepsy? The answer is not cut-and-dry. Thomas S. Kilduff, Ph.D. is the 2017 recipient of the Sleep Research Society’s Distinguished Scientist Award. In an interview in Sleep Review, Dr. Kildruff discusses his research on the connection between narcolepsy and hibernation. He has discovered that hypocretin or orexin cells are associated with hibernation in animals, and narcolepsy in humans.

While narcolepsy doesn’t cause humans to go into hibernation, it does cause their metabolisms to drop and their bodies to prepare for this type of deep sleep. Dr. Kildruff is currently working on a study to identify how a defect of the human hypocretin or orexin cells can be resolved by using cells from hibernating animals. Thanks to hibernating mammals, humans with sleep disorders may have a new treatment regime in the near future.

Hibernation in a Nutshell

As it turns out, hibernation is a highly detailed process that affects all mammals. So this winter when you are out hiking on snowy trails or camping in the forest, consider all of the deeply-sleeping animals tucked into caves and leafy abodes. And by all means, never try to wake a hibernating bear…or any hibernating creature for that matter.

P.S. If you noticed the illustration at the top was of a pig – good for you! We know pigs don’t hibernate. Just testing to see how awake you are.