Scientists have long wondered just what takes place within the body of a bear in the wild while it hibernates. And now, they can eliminate a good deal of the guesswork in such speculations, thanks to a new study at the University of Alaska's Institute of Arctic Biology. Researchers at the institute erected boxes for bears to sleep in that enabled researchers to monitor the bears' vital signs--and have provisionally concluded that hibernating bears are nothing less than "a metabolic marvel."
The boxes are ensconced in what the research team calls "hibernaculums" -- artificial caves outfitted with electronics. As the institute explained in a press release, "technical limitations" -- i.e. the risk of mauling -- have prevented earlier students of bear behavior from monitoring long-term patterns of hibernation. But by deliberately designing the hibernaculums to the specifications of a winter-weary bear, the researchers say that they've cleared that hurdle. Among their early findings is the revelation that a bear's metabolism lowers as much as 75 percent during hibernation, even as its internal body temperature remains steady.
"Bears don't eat, drink, urinate or defecate for six or seven months," Brian Barnes, the director of the project, told NPR. "They make their own water, probably by metabolizing fat, and they get rid of wastes by breaking them down internally. They're a closed system. All they need is air, and they can do just fine." This video has more on the mechanics of hibernation, and, in case you were wondering, the video below shows that a bear does indeed snore like, well, a bear.
The researchers implanted the five American black bears in the study with radio transmitters to record body temperature, heartbeat and muscle activity. They found that hibernating bears only breathe one to two times per minute and their heart slows considerably between breaths -- with the interval between beats lasting up to 20 seconds.
"Each time the bear takes a breath, the heart accelerates for a short time to almost that of a resting bear in summer," the group's Øivind Tøien said. "When the bear breathes out, the heart slows down again, and there will be another 30 to 60 seconds until the next breath."
(Photo and video via: Øivind Tøien/Institute of Arctic Biology, University of Alaska Fairbanks)