Though bears and ground squirrels evolved to hibernate — and many are successful hibernators — moving in and out of hibernation or torpor can be stressful events, especially in the case of ground squirrels.
Each fall, Katmai National Park holds a competition as Alaska’s brown bears finish fattening up for their long winter hibernation.
In black bears, Kelly regularly observes November hibernation heart rates of 50 beats per minute.
Even though the scientific community was once largely on the fence about whether bears are true hibernators — because they can’t dramatically drop their core temperature to freezing or below freezing temperatures — their torpid state was always considered an extraordinary feat, especially for so large an animal.
"For the longest time, I would say they’re not real hibernators," Frank van Breukelen, who researches hibernation and biochemical adaptation at the University of Nevada-Las Vegas, said in an interview.
Bears — like those still fattening up in Katmai National Park — are often given more overt clues. Their world changes. The fish rot. The berries disappear. The forests brown.
Fat Bear Week bears are preparing for hibernation.
When fall arrives, some animals, like the ground squirrels Carey studies, suddenly depress their metabolisms, which is a process called torpor.
"I always call this the magical time of year," Hannah Carey, who researches the physiology of hibernating animals at the University of Wisconsin-Madison’s School of Veterinary Medicine, said in an interview.
During winter hibernation, a bear can lose up to one third of its body mass. #FatBearWeek pic. twitter.
Hibernating animals — including ground squirrels, groundhogs, and bats — slow their breaths, reduce their heartbeats, and substantially wind down, or depress, their metabolisms.
"It’s still a little controversial," Marcella Kelly, a Virginia Tech ecologist who performs research at the university’s Black Bear Research Center, said in an interview.
Bear hibernation is a superpower, but it comes with a cost https://t.co/ZgYmoFu3db— Mashable (@mashable) September 8, 2020
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