Hibernation in Black Bears: Independence of Metabolic Suppression from Body Temperature
Abstract
Black bears hibernate for 5 to 7 months a year and, during this time, do not eat, drink, urinate, or defecate. We measured metabolic rate and body temperature in hibernating black bears and found that they suppress metabolism to 25% of basal rates while regulating body temperature from 30° to 36°C, in multiday cycles. Heart rates were reduced from 55 to as few as 9 beats per minute, with profound sinus arrhythmia. After returning to normal body temperature and emerging from dens, bears maintained a reduced metabolic rate for up to 3 weeks. The pronounced reduction and delayed recovery of metabolic rate in hibernating bears suggest that the majority of metabolic suppression during hibernation is independent of lowered body temperature.
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Science
Volume 331 | Issue 6019
18 February 2011
18 February 2011
Copyright
Copyright © 2011, American Association for the Advancement of Science.
Submission history
Received: 22 October 2010
Accepted: 13 January 2011
Published in print: 18 February 2011
Acknowledgments
This work was supported by U.S. Army Medical Research and Materiel Command grant 05178001; NSF grants 9819540, 0076039, and 0732755; NIH HD-00973; and gift funds to Stanford University, American Heart Association #0020626Z, and the Fulbright Program. We thank the Alaska Department of Fish and Game for providing bears, D. Ritter for technical assistance, and J. Kenagy and J. Duman for comments.
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