Denning

Denning serves as a way for bears to not only survive, but successfully produce offspring

Photo by Ben Augustine

during the cold winter months when natural foods are almost nonexistent. While black bears are often referred to as “hibernating” during the denning period, this is actually not the case. Rather, bears enter a sleep-like state referred to as “winter torpor” in which they are fully capable of moving and even exiting the den. During that time, their metabolism slows so that all reserve energy is used for basic life functions and milk production for cubs. This is why fall food abundance prior to denning, primarily in the form of acorns, is critical for black bears in the Southern Appalachians.

Timing of den entry varies considerably and is primarily determined by sex, reproductive condition, and fall food availability. In Kentucky, females typically enter dens from mid-November to December. Collectively, female bears den before males, and pregnant females or those with offspring den before solitary females. Sometimes older males den for relatively short periods, and may travel a bit before denning in another location. That is especially true if there is ready access to garbage or other human-related food source during the winter months. During poor mast years, however, bears den later as it takes longer to acquire enough to make through the 3–4 month denning period in which bears do not eat, drink, urinate, or defecate.

Bears in Kentucky usually den in rock cavities, hollow trees, or open dens in thick brush piles. Cubs grow rapidly as their diet consists exclusively of high-calorie and fat-rich milk provided by the mother’s fat reserve from the previous winter’s hard mast consumption. Females with offspring generally emerge from dens in March or April. Females with offspring remain together throughout the second winter in which they again den as a family unit. At about 16 months of age the yearling bears disperse soon as the mother comes into estrus in preparation for the breeding season.