10 Eye-Opening Facts About Hibernation

You're not the only one who didn't want to wake up this morning...

1. Beware "hibernating" bears. They actually spend winters in a lighter-sleeping torpor—and they'll be grumpy (and maybe grisly) if woken up.

2. The big difference between torpor and hibernation? Torpor is usually shorter-term and in response to environmental temperature and food availability. Longer-term hibernation is driven by day length and hormonal changes.

3. Animals kick back and relax. Their body temperature and heart rate drops and their breathing and metabolism slow. Hibernating bats can go up to an hour between breaths!

4. Depending on the animal, torpor can last a few months (bears) or even just a few days (prairie dogs or ground squirrels).

5. Just because they're resting, it doesn't mean they're not getting stuff done. Bears give birth during torpor and nurse their cubs. Birds have been known to get some zzz's while incubating their nests.

6. Even hibernators aren't out cold. They wake up from their deep sleep to drink water, warm their bodies back up, or occasionally move to a new nest or den. Then they go back to sleep. Their central nervous system sounds the alarm when it's time to wake up for good.

7. Some animals estivate, which means they rest during periods of drought and heat. Hedgehogs, salamanders, and lungfish are all estivators.

8. Wood frogs are the most extreme hibernators—65% of the water in their bodies turns to ice during the winter. The frogsicles stay frozen for up to seven months before thawing out just fine.

9. The common poorwill is the only bird known to hibernate for months at a time. Scientists didn't discover this until the 1940s, but the Hopi people of the Southwest knowingly called the species "the sleeping one."

10. There's still a lot to learn about hibernation—and for good reason. Hibernation has been shown to repair brain and cell damage in animals while maintaining skeletal muscles. In the future, lowering body temperature and slowing metabolism by inducing human hibernation could help people recover from strokes and other trauma. It could also come in handy someday during long-term space travel.