Hibernation Explained: Do Not Disturb

by AMNH on

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Hibernation helps animals like bears, bats, and even frogs survive during lean times. But resting for months at a time also leaves them vulnerable.


Black bear walks through a grassy field on a sunny day.
For hibernating animals like black bears, waking up early can be disastrous.
Courtesy of Pixabay

For famous hibernators like black bears, predators such as mountain lions can present a threat during their winter rests. A more common one, though, is humans—not because they will attack a bear, but because they can wake it up.

Whether it’s a neighbor’s car alarm or the family dog needing an early walk, no one likes being pulled out of bed earlier than planned. For hibernating animals, an early wake-up call isn’t just an inconvenience—it can be downright lethal. Waking up from hibernation requires a lot of energy, depleting reserves that are key to surviving the winter.

It’s not just bears that are in danger if they wake up from hibernation at the wrong time. In colder areas of North America, many bats species sleep through winters in caves, mines, and other large roosts, known as hibernacula.


14 or more bats with eyes closed and wings folded huddle on top of one another in a cluster.
In winter, many bat populations huddle together in roosts known as hibernacula.
Courtesy of USFWS/A. Froschauer

In recent years, these populations have been devastated by a disease known as white-nose syndrome, which is caused by the fungus Pseudogymnoascus destructans. The fungus itself isn’t deadly to bats, though.

“What kills the bat is that the fungus makes them wake up, which is very costly,” says Nancy Simmons, curator-in-charge in the Museum's Department of Mammalogy whose research specialty is bats. “If they wake up too many times, it burns up all the fat they had stored for the winter.”


A version of this story originally appeared in the winter 2017 issue of Rotunda, the Member magazine.