Male bears are called boars and female bears are called sows. Brown bears gain an average of 3-6 pounds of fat per day during peak periods to obtain enough body weight to survive winter hibernation. Hibernation is a state of dormancy at which time bears are inactive, allowing them to adapt to short winter food supplies. During a bears hibernation, its body temperature is close to that of the surrounding air, its metabolic rate is comparatively high and it may awaken and move about outside the den. The length of a bears hibernation depends on climate, location, sex, age and reproductive status of the individual bear. Bears that have not obtained an adequate fat reserve may not hibernate at all. Spring Bears Summer Bears Fall Bears