Why don't hibernating bears muscles atrophy?
Posted by Ellen Lougee on July 30, 2005
Q: Why don't the muscles of hibernating bears atrophy? If I slept for even a month my muscles would be so weak I wouldn't be able to stand up. How do they do it?
Thanks,
Ellen
A: This is a complex issue that is not yet completely understood that involves the physiology of many mammals . I've found a few sites that offer info that I hope will help or at least get you started.
However I would like to point out that bears don't hibernate! Oh, I know, everyone talks about hibernating bears but in fact, they don't. Bears go into what scientists call "carnivorean lethargy" which is a dormant state that is not as profound as hibernation. Those animals that DO hibernate include the Groundhog, jumping mice, many bats, and ground squirrels.
Mammalian Hibernation Definition: Mammalian hibernation is a strategy employed by many small animals to live through long winter months of subzero temperatures and little or no food availability. During hibernation, metabolic rate is strongly suppressed, heart rate and respiratory rates drop to low levels, and body temperature is allowed to drop to ambient [1]. The little brown bat, M. lucifugus, characteristically spends eight months of a year hibernating. Prior to entering hibernation, bats select roosting spots where temperatures do not rise above 100C, allowing them to prepare for hibernation by entering torpor for up to 14 hours at a time [2]. Once hibernation begins, torpid bouts can last for weeks with animals waking up intermittently for up to a day before re-entering torpor. It is estimated that hibernating mammals can conserve up to 88% of the energy that would otherwise be required to remain awake in an euthermic state over winter [3].
Info on Bear dormancy:
Bears not true hibernators:
Thanks for an excellent question. Sorry I'm not up on this enough to answer fully.
John Wiessinger ( July 31, 2005)