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Bear hibernation study finds surprises in search for clues to help human health

An infrared camera captures an Alaskan black bear in deep hibernation. For the first time, researchers watched bears slumber all winter, discovering that the famous hibernators maintain a relatively high body temperature even as their breathing, heart rate, and metabolism drop far below normal.

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Washington Post Staff Writer
Friday, February 18, 2011; 12:55 AM

Call this study "Big Brother" black bear.

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In the woods of Alaska, five black bears snoozed all winter while researchers recorded every detail of their slow-motion daily drama for the first time.

Cameras caught them shuffling around every day or so.

Oxygen and carbon dioxide monitors kept tabs on their metabolism.

And sensors implanted in their abdomens recorded their heart rate and breathing.

It's more than reality show contestants usually have to put up with.

And yet, these scientific stars performed perfectly, offering an unprecedented glimpse into the secrets of hibernation.

It turns out that Ursus americanus hibernates in a manner unlike that of the dozens of other hibernating mammals. The biologists saw that the animals' heart rate dropped precipitously, they breathed just two or three times a minute and their metabolism slowed to a trickle as the animals slowly burned the fat they spent all summer accumulating.

None of that was unexpected.

And yet, unlike other hibernators such as squirrels, chipmunks, raccoons and skunks, the bears maintained a high body temperature throughout five months of inactivity.

Further, when the bears emerged in mid-April, the researchers got another surprise. Like a fuzzy-headed human waking from a Sunday snooze, the bears stayed groggy, with their metabolic rate remaining at about half that of summer levels for two to three weeks.

"The slow emergence from hibernation was very surprising," said Oivind Toien, a biologist at the Institute of Arctic Biology at the University of Alaska at Fairbanks, who cross-country skied to a control hut near the dens every morning for five months.

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