Five stages of black bear activity and hibernation



According to Sharon Herrell, the senior bear keeper at the North American Bear Center, the annual cycle of black bear activity and hibernation has five stages. The stages differ in biochemistry, physiology, appetite and level of activity. The following is a brief description of each of the stages: • Hibernation of study bears in close dens experience continuous dormancy with distinct decreases in heart rate and metabolic rate. They do not eat, drink, urinate or defecate. • Walking hibernation is the two to three weeks following emergence when the bears’ metabolic processes adjust to normal summer levels. During walking hibernation, bears voluntarily eat and drink less than they will later during normal activity. • Normal activity typically lasts from green-up in the spring to the onset of hyperphagia in midsummer or fall, depending upon the region. • Hyperphagia is a period of excessive eating and drinking to fatten for hibernation. Large amounts of water are needed to process the large amounts of food and rid the bear’s body of nitrogenous waste. • Fall transition is the period after hyperphagia when metabolic processes change in preparation for hibernation. Bears voluntarily eat less but continue to drink to purge body wastes. They become increasingly lethargic, resting 22 or more hours per day, often near water.

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