Hibernation of the Black and Brown Bear Bobby Bennett Winter Ecology Field Course Spring 2006 Mountain Research Station University of Colorado, Boulder
Typical Hibernation Patterns • Bears do not feed for 7 months, living off body fat until late spring. • They rely of their fur for insulation, which doubles its insulation capacity in winter • They construct some sort of den • Both sexes have a 99% survival rate in winter (Heinrich, p.76)
Hibernation Metabolic Processes of Both Species • Heart rate may decline to 8 beat/min • Leptin, a hormone, controls appetite during hibernation • A Satiety (Heinrich, p.256) • Body temps drop to 35 degrees (37-38 when active) • Doesn’t characterize bears hibernation
Other Bodily Processes • Water balance • They usually do not urinate during the winter • Nitrogen wastes biochemically recycle back into proteins as to not poison the bear • This also prevents muscle mass loss due to no exercise (Heinrich, p.259)
Black Bear “Easily food conditioned; extremely clever, creature of habit; inquisitive; playful” (Brown, p.94) Brown Bear “Dignified; deliberate, fearless, bold, generally peaceful; solitary” (Brown, p.94) Black and Brown Differences?
Black Bear Adds 4 in. of fat prior to hibernation Dens under large boulders, scraped out depressions under brush, in tree routes, caves, under logs, possible in trees, under buildings 20% steep slope (Brown, p.150) Brown Bear Adds 6-8 in. of fat prior to hibernation Dens dug in dry earth, under large boulders, located above valley floor 30% steep slope Slope aspect depends of exposure 61% on north slope in Rocky Mnts. (Brown, p.150) Hibernation Differences
Hibernation Differences Cont. • Brown bear hibernates as early as September in northern regions • Black bears may not even hibernate during mild winters (Brown, p.145)
conclusion • Brown Bear and Black Bear have very similar hibernation patterns despite geographic ranges • The proportionally larger Brown Bear packs on more fat prior to hibernation • There are differences in den characteristics for both species • But… as far as my research has led me, both bears have very similar hibernation/winter-time physiology and behavioral characteristics • What’s Next? Even More Research
Bibliography Brown, G. (1993). The Great Bear Almanac. Lyons & Burford, Publishers. Heinrich, B. (2003). Winter World: The Ingenuity of Animal Survival, First Ed. HarperCollins Publishers Inc. Laycock, G. (1986). The Wild Bears. Outdoor Life Books. Manning, A., Dawkins, M.S. (1992). Animal Behavior, Fourth Ed. Cambridge University Press.