(Jessi yawns) I just got up from a long nap.

It feels really great to get some rest. And outside, there are lots of animals just getting ready for a very long rest, because it’s going to be winter soon.

Animlas like groundhogs! Groundhogs are little animals that are about half a meter long. They live in the United States and Canada, and spend a lot of their time in burrows that they dig into the ground.

And right now, groundhogs are trying to get everything ready for a perfect, cozy den. They’re preparing for hibernation. Hibernation is like a deep, deep sleep that some animals go into during the winter.

They’ll sleep for months and months, and they don’t wake up until spring. [Squeaks squeaks] Those groundhogs aren’t necessarily sleepy, Squeaks. Hibernation is a way for animals to survive the colder winter months. You see, animals normally need plenty of food to survive.

But during cold winter months, lots of the food that animals like to eat goes away. In snowy, cold places, the leaves fall off of trees, fruit stops growing, and even the bugs go away. For animals that eat these things, it can be a hungry few months.

To survive, some animals will migrate, meaning they’ll travel somewhere else where there’s more food. Like birds that fly to somewhere warmer. Others, like squirrels, will store food away to eat when it's cold.

But animals like groundhogs can’t move somewhere else, and they can’t store enough food to last all winter. [Squeaks squeaks] That's right, Squeaks, they have to hibernate. If a groundhog is hibernating, it doesn’t matter if there isn’t a lot of food around, because the groundhog is fast asleep. [Squeaks squeaks] I know you still need to wake up and eat after sleeping, but it’s different for hibernating animals, because hibernating is more than a long nap. Animals spend a long time preparing for hibernation.

Before they hibernate, a groundhog will spend weeks eating as much as possible. That little groundhog becomes a great /big/ groundhog, with a thick layer of body fat. Then, once it’s time, they'll cuddle up in its burrow, and go to sleep.

Now, /normally/ when a groundhog goes to sleep, their body rests a bit, but their lungs keep breathing and their heart keeps pumping blood normally. To keep working, the groundhog’s lungs and heart need energy from the food it eats. But during the type of very deep sleep the groundhog goes into when they hibernates, its lungs and heart slow /way/ down.

Its heart only beats about five times a minute, and it only breathes about twice a minute! They go so slowly, they don’t use as much energy. And since the groundhog’s body isn’t using very much energy, they don't have to wake up every day to eat more food.

Instead, it can use the energy they've already has stored. [Squeaks squeaks] That’s right, Squeaks! The groundhog uses the energy it stored up from eating all of that food in the weeks before they hibernated. The layer of fat the groundhog put on in the fall slowly gets used up for energy.

And by the time the groundhog needs to wake up to eat, it’s time for spring! Lots of different animals can hibernate, like bats, chipmunks, and hedgehogs. Bats will even hibernate in large colonies, all huddled together to share warmth. [Squeaks yawns] Whoa!

I don’t know if robots need to hibernate, Squeaks. But maybe it’s time for you to take a nap. What do you think it would be like to hibernate all winter long?

Can you think of any other animals that rest during the colder months? Ask a grown-up to help you leave a comment below, or send us an email at kids@scishow.com. Thanks, and we’ll see you next time, here at the fort.