10 unexpected facts about bear hibernation

While most of us feel like waiting out the chilly winter under a big, fluffy duvet, bears’ hibernation takes cold-weather sleep to a whole new level. Here are some cool facts you may not have known.

While both male and female brown and black bears hibernate, only pregnant polar bears den up for the winter.

Bears stay in a state of "waking hibernation" for several weeks after they wake up. They may act like they're drunk, or really, really tired.

Bears fatten up a lot before going into hibernation. In fact, a hibernating adult male may have more than a million calories stored.

Bears sleep all winter — but pregnant females will wake up to give birth. If she hasn't stored up enough energy, though, she won't have cubs that year.

Bears can handle the cold, but they can't survive without food. Because food is scarce in the winter, they hibernate instead. In places where food is available during the winter, bears won't hibernate.

Unlike rodents, who face the risk of freezing to death during the winter, bears' body temperatures go down less than 10 degrees.

During hibernation, a bear's heart rate goes from 50 to 10 beats per minute.

During hibernation, a bear re-absorbs its feces and urine — so it never needs to get up to pee in the middle of the night.

Bears lose between 25 and 40 per cent of their body weight while they sleep the winter away.

A bear will lose its paw pads during hibernation, and new ones will grow.