Bears will seek out caves, dig a den, or use a hollow log or dense undergrowth as their winter hiding place. In areas with a more moderate climate and a short period when food is not available, black bears either do not hibernate or they spend short periods of time resting in a den. Hibernation is more than just sleep. The bear's metabolism slows by more than one-half. Their heart rate drops to eight to twelve beats per minute.
Black bears have a unique reproductive cycle.
The fertilized egg floats freely in the uterus for as long as six months with no development. Once the female begins to prepare for hibernation, the egg attaches itself to the uterine wall, but only if the female has enough body fat to carry her and her cubs through the winter. Otherwise the egg will be reabsorbed. The cubs are born while their mother is hibernating. The average litter size is two.