Snooze Crew

What do animals do in the winter? Some head south to warmer places. Some grow a thick coat of fur. The fur traps heat close to their bodies. Others snooze until spring in a state called hibernation.

Hibernating animals spend the winter in a deep, sleep-like state. Their body temperatures drop. Their heart rates and breathing slow down. They don’t eat or drink until spring. Hibernation helps animals survive the time of year when food is scarce. Learn about some amazing things these four hibernating animals do during their long snooze.

Black bears stuff themselves with food in the fall. They eat nuts. They gorge on berries. They devour insects. Gaining weight helps them hibernate throughout the long winter. Black bears must increase their weight by at least 33 percent each fall. The weight gain helps them to survive until spring.

Rapid weight gain can put humans at risk for serious problems. One problem is type 2 diabetes. A body with type 2 diabetes can’t process sugars from food properly.

Bears develop a type of diabetes while they hibernate. Their diabetes goes away in the spring. Scientists discovered last year that bears produce a special substance. This substance adjusts how their bodies process sugar. Scientists are studying the substance. They hope to use what they learn to create a medicine for humans.

Cold weather drives insects away. That’s why many species of bats curl up for the winter. The bats sleep in caves. They also sleep in mines and tunnels. These places have humid air. The temperature of the air never drops below freezing. Scientists call these winter bat homes hibernacula. Sometimes 300,000 bats huddle together in a single site!

Typical hibernators rest through the winter. Bats don’t. They enter a state called torpor.

Bats wake up every few days to pee and poop during torpor. They also wake up to eat. Scientists are studying bats’ cycle of waking and sleeping during this state. They want to see how it affects bats’ memories.

Arctic ground squirrels live in the coldest parts of the world—the northernmost parts of North America and Russia. 

In the summer, these squirrels feast on plants. They double their body weight, storing up energy for hibernation. 

The squirrels also lower their body temperature to -2.9°C (27°F) to save energy during winter. Any other mammal would die with a body temperature that low, says biologist Cory Williams. 

Arctic ground squirrels live in the northernmost parts of North America and Russia. These are the coldest parts of the world.

In the summer, arctic ground squirrels feast on plants. They double their body weight. They store up energy for hibernation.

The squirrels also lower their body temperature to -2.9°C (27°F). This helps them save energy during winter. Biologist Cory Williams says that any other mammal would die with a body temperature that low.

Winters in North America can be harsh. But that’s no problem for gray tree frogs. They can survive at temperatures as low as 18°F! The frog doesn’t just cool down its body like the ground squirrel. It actually freezes! Ice forms in the spaces between the frog’s cells. 

Being frozen would kill most other creatures. But this frog has a trick to survive. Its body makes a substance that prevents the ice from damaging the frog’s cells and tissues. Scientists study this substance to learn how to better preserve human tissues without damaging them. 

Winters in North America can be harsh. That’s no problem for gray tree frogs. They can survive at temperatures as low as 18°F! The frog doesn’t just cool down its body. It actually freezes! Ice forms in the spaces between the frog’s cells.

Being frozen would kill most other creatures. But this frog has a trick to survive. Its body makes a special substance. This substance prevents the ice from damaging the frog’s cells. It also protects the frog’s tissues. Scientists study this substance. They want to learn how to preserve human tissues without damaging them.