Five Winter Sleepy Heads

- Tucker Smith, Guest Contributor

This week was the Winter Solstice––the first day of winter in the Northern Hemisphere. If the cold months ahead are already making you want to curl up under the covers, take some tips from these five pros who will spend their winters hibernating.

Photo Credit: Mike Carraway, ncwildlife.org

Bears 

This animal may be the most famous hibernators. Through late summer and fall, bears double their diet to prepare for hibernation. Bears hibernate in their dens, which they can make in any small open space: a hollow tree, a cave, a rock crevice, an underground root system. Bears rarely hibernate in the same place twice. To learn more about bears’ hibernation, check out this 2018 Nature News article.

Photo Credit: BirdHunter591, istockphoto.com

Bats 

Not all bats hibernate––some migrate like birds to warmer climates––but those that do enter a special kind of hibernation called torpor. In torpor, a bat’s internal functions decrease at extreme rates, with its heart rate dropping from 200-300 beats per minutes to 10 beats per minute. Unlike other hibernators, bats can go in and out of torpor on a varying schedule. Their winter hibernation is broken by periods of wakefulness when their body functions return to normal and they can eat. 

Photo Credit: earth.com

Bumblebees 

Where do bumblebees go in the winter? For most of them, winter is the end of their life cycle. For the queen bee, though, winter is the time to hibernate. After filling up on pollen, the queen digs herself a hole in well-drained soil. This hole is where she will spend the colder months of the year, and it has to be cozy––some queen bees hibernate for up to 9 months at a time! Bumblebee hibernation holes are 10 cm or deeper, and they allow bumblebees to survive subzero temperatures. When she wakes up in the spring, the queen bee will be ready to start her new colony.  

Photo Credit: Dana Montague, scenichudson.org

Chipmunks 

Chipmunks are well-known for hoarding food (a single chipmunk can collect 165 acorns in one day!), so it’s no surprise that these little critters like to eat. Like bats, Eastern chipmunks enter torpor instead of hibernation, so they can spend a few days eating between sleep cycles. This is because chipmunks don’t develop additional body fat for the winter––instead, chipmunks’ fur fluffs up in the winter to insulate them against the cold. 

Photo Credit: Todd Pierson, herpsofnc.org

Wood Frogs 

Most frogs in the northern hemisphere hibernate in the winter. They sleep deep underwater, where their body temperature cools but never drops below freezing. Wood frogs, on the other hand, hibernate under a forest floor’s litter of leaves. Their bodies are built to withstand the freezing temperatures that would cause deadly damage to other animals: the excess glucose generated by the wood frog’s liver prevents its cells from freezing and keeps water inside the cells to stop dehydration. With this internal protection in place, the wood frog allows ice to fill its abdominal cavity, encasing its internal organs. Because wood frogs stay on land, they wake from hibernation before other frogs and can take advantage of spring’s early resources.