10 Fascinating Facts about Hibernation

10 Fascinating Facts about Hibernation
Reading Time: 4 minutes

Animals that hibernate seem to have the right idea: Head indoors, hang up the ‘Do not disturb’ sign and catch some Z’s until Spring returns. Or do they? Several animals may seem to snooze away the long dark winter days, but that isn’t what actually happens. Here are some surprising facts about what happens to animals during hibernation. (And why humans can’t hibernate.)

Picture of a hedgehog sleeping hedgehog lying on its back on a bed of autumn leaves in hibernation.

Does hibernation mean sleeping?
Hedgehogs, bears, bats and other animals aren’t really sleeping during hibernation. As this article from Woodland Trust explains, hibernating animals enter a state of inactivity where their heart rate and breathing slows, and their body temperature and metabolism drops. The body temperature of the Artic ground squirrel can drop to below -2°C while a bat’s heart rate can drop from 400 to 11 beats per minute.

Picture of a crocodile’s head half in and half out clear water in hibernation.

Do animals only hibernate in winter?
Animals don’t only hibernate during winter. In hot and dry climates, creatures like the African hedgehog aestivate. Hibernation and aestivation aren’t the same. Think of hibernation as long winter sleep and aestivation as a summer siesta. When animals aestivate it’s for a much shorter period than hibernation, but it’s for the same reason – to conserve resources.

In hot weather or when their food supply is scare, animals will look for a cool, moist, shady sleeping spot to conserve energy and resources while they hide away from the heat. Many different animals including the African lungfish, desert tortoises and crocodiles take a summer snooze.

A bearded dragon lizard in hibernation on a sandy-coloured brick wall

Do reptiles hibernate?
Mammals are warm-blooded, or endotherms. This means creatures like us humans, cats and dogs can regulate their own body temperatures. Reptiles are ectotherms, or what we also call cold-blooded, and their body temperature is regulated by their environments.

When cold weather sets in, reptiles including tortoises, snakes and lizards brumate. During brumation animals shut down their bodies to conserve energy. Snakes often seek out a vacant rodent burrow and settle in for winter while other animals like the gopher tortoise will dig itself a burrow in the ground. People who keep bearded dragons as pets notice their beardies slow down, eat less and sleep more during the cold months.

Animals that brumate may emerge briefly to eat or drink before heading back to their hidey holes to wait out the cold until warmer weather returns and their bodies can warm up.

Picture of a bear in the river with a salmon in its mouth

How do animals get ready for hibernation? 
During hibernation, animals like hedgehogs and bears live off their natural body stores. This means they need to eat a lot before hibernation to make sure they have enough to make it through winter. Bears eat and drink nearly non-stop during autumn. In Yellowstone National Park, bears can gain up to 3lbs (that’s almost 1.5kg) a day!

Some animals like mice prepare a den and line it with leaves and paper to make it warm and cosy. Snails attach to a place, cover themselves in their own slime and wait out winter.  

Cute picture of a squirrel wearing a purple sleeping cap standing next to an old-fashioned white alarm clock

How do animals know when it’s time to wake up?
Not all animals start or wake from hibernation at the same time. It’s all dependent on the animal species and where they live. Animals instinctively know when to start eating more to prepare for hibernation. The same is true for when it’s time to wake up and this is normally when their food becomes available again.

Cute picture of a small boy asleep in bed with his dog sleeping close next to him

Can humans hibernate?
It’s tempting to hide under the duvet during winter and snooze away the cold days, but that’s not really hibernation because humans can’t hibernate.

Animals hibernate for two reasons, cold weather and a lack of food. Early humans evolved in equatorial Africa and didn’t need to escape harsh weather conditions or were not likely to have experienced a shortage of food. Scientists also suspect we may be too big because except for bears, most creatures that hibernate are small.

However, scientists are researching how humans can hibernate in space to help people cope with long periods of space travel. Studying animals is helping scientists figure out how astronauts could potentially survive long periods of space travel. It’s estimated that it could take months for astronauts in journeys like SpaceX’s Mars Mission to reach their destination. Human hibernation, known as hypersleep, could make it easier for humans to travel through space. But it’s only science fiction for now.

Close up picture of a frog submerged in a frozen river

4 more fascinating facts about hibernation:

  1. When you’re thinking of Arctic animals, frogs hardly leap to mind. But a species of wood frog in North America and Canada can survive with more than half its body in a frozen state. These ‘frogsicles’ can survive several periods of freezing and thawing during a single winter thanks to a special protein in their blood.
  2. Echidnas hibernate during bushfires. These hedgehog-like animals in Australia often live in underground burrows or hollowed-out logs. They stay hidden away and wait out bushfires until it’s safe to emerge and forage for food.
  3. What animal hibernates the longest? A dormouse can hibernate for up to 11 months in the wild, provided they’ve eaten enough. In fact the name dormouse comes from the French ‘dormir’ meaning ‘to sleep.’
  4. The word hibernate comes from the Latin Hibernaculum meaning ‘winter residence.’