Nov Bear Hibernation: 5 Fun Facts. November 2, Bears , Wildlife. Here are some facts that may surprise you about bear hibernation. Bears eat… a lot. Baby bears and hibernation are related! Bears create their own heat-efficient hideaways. The cubs are born in late January or early February and are naked, blind, and helpless Rogers They measure only about 8 inches 20 cm long and weigh from 8 - 12 ounces - g. The newborn cubs do not hibernate.
They sleep next to their mother, nurse, and grow rapidly. When black bear cubs emerge from the den at about three months of age, they weigh about 4 - 8 pounds 1. At ten weeks of age, grizzly bear cubs weigh 10 - 20 pounds 4. When temperatures warm up and food is available in the form of winter-killed ungulates or early spring vegetation, bears emerge from their dens.
Males, subadults, solitary females, and females with yearlings or two-year-olds usually leave the vicinity of their den within a week of emergence while females with new-born cubs remain in the general vicinity of the den for several more weeks Lindzey and Meslow , Haroldson et al. Several physiological processes bears undergo during hibernation are of interest to medical researchers. When bears are hibernating and metabolizing body fat, their cholesterol levels are twice as high as during the summer and twice as high as the cholesterol levels of most humans Baggett Bears, however, do not suffer from hardening of the arteries arteriosclerosis or gallstones, conditions which result from high levels of cholesterol in humans.
The bear's liver secretes a substance that dissolves gallstones in humans without surgery. Another mystery of hibernation is that bears do not lose bone mass during hibernation. All other mammals which maintain non-weight bearing positions for an extended period of time suffer from osteoporosis, or a weakening of the bones Wickelgren When the substance responsible for this phenomenon is discovered it may help people who suffer from weak bones. Beecham, J. Reynolds, and M. Black bear denning activities and den characteristics in west-central Idaho.
Bear Res. Brown, G. The Great bear almanac. Lyons and Burford, publishers. New York, N. Craighead, F. Grizzly bear prehibernation and denning activities as determined by radiotracking.
Haroldson, M. Ternent, K. Gunther, and C. Grizzly bear denning chronology and movements in the Greater Yellowstone Ecosystem. Ursus Jonkel, C. Black, brown grizzly , and polar bears. Stackpole Books, Harrisburg, PA. Judd, S. Knight, and B. Denning of grizzly bears in the Yellowstone National Park area. Kolenosky, G. Winter denning of black bears in east-central Ontario.
Lindzey, F. Winter dormancy in black bears in southwestern Washington. Linnell, J. Swenson, R. Bears around Ely usually continue hibernating through winter thaws. The activity schedule is very different in eastern North America where acorns, hickory nuts, beech nuts, and other foods become available in fall and some foods remain available all winter.
Bears there are genetically programmed to delay hibernation until late November or December and hibernate less than 5 months.
Hibernation there is typically not as deep, and some bears emerge to forage during winter thaws. Food sometimes remains available throughout winter there, and some bears continue foraging throughout winter. Stage 1 — Hibernation of study bears in close dens is continuous dormancy with distinct decreases in heart rate and metabolic rate. They use up to 4, kcal per day, mainly body fat, and do not eat, drink, urinate, or defecate. Blood perfusion rates of peripheral tissues can fall below levels needed for aerobic metabolism in humans.
They also lick up drops of meltwater, eat snow and icicles, urinate, and defecate. Stage 2 —Walking hibernation is the weeks following emergence when metabolic processes adjust to normal summer levels. During walking hibernation, bears voluntarily eat and drink less than they will later during normal activity.
They also excrete less urine, nitrogen, calcium, phosphorus, and magnesium. Stage 3 —Normal activity typically lasts from green-up in spring to the onset of hyperphagia in midsummer or fall, depending upon region. During this stage, bears with unlimited food eat 5, to 8, kcal per day.
If they are denied water and food during this stage, they cannot duplicate hibernation responses. Instead, they become dehydrated, utilize muscle for energy, and accumulate nitrogenous wastes in the blood, which can be fatal. Stage 4 —Hyperphagia is a period of excessive eating and drinking to fatten for hibernation. Black bears with unlimited food and water ate 15, to 20, kcal per day and drank several gallons.
Large amounts of water are needed to process the large amounts of food and rid the body of nitrogenous waste. Daily urine volumes for two bears were gallons liters. Nitrogen losses were 2. Stage 5 —Fall transition is a period after hyperphagia when metabolic processes change in preparation for hibernation.
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