Hibernation of female bears is a unique mechanism of adaptation to the harsh weather conditions of the taiga forest. Staying in a den allows the female bears not to worry about food in the coldest time of the year and to produce offspring in relatively protected conditions.
How does a polar bear sleep in a den?
Hibernation for bears is a special period, since at this time the animal not only waits out the coldest season, when the amount of food drops sharply, but also acquires offspring. It is believed that bears of all kinds, regardless of gender, hibernate, but this is far from the case. For example, male polar bears do not hibernate, but spend the whole winter on the ice, actively hunting and fattening for the coming summer.
However, polar bears are forced to hibernate and the reason for this is the need to produce offspring. In the habitat of polar bears, a significant layer of fat is required for survival, which newborns do not have. That is why polar bears make large dens in the snowdrifts, in which the temperature never drops below 0 ° C. Thus, the cubs, warmed by the warmth of their mother, can gain weight by feeding on fatty milk. Polar bears spend about 6 months in a den so that the cubs can grow strong enough to live in a frozen world where ice reigns around.
Brown bear wintering
Brown bears hibernate regardless of gender, but females of this species still have their own unique characteristics. Bears reproduce in a den, but in order to gain fat, they need to take advantage of all the nutritional opportunities available in summer. Female bears mate in early spring, but are able to postpone pregnancy. Thus, they time the cubs to appear in a den, protected from predators.
Bears prefer to equip dens not in cold snow, but under large snags of age-old trees or in specially dug cavities in ravines. The temperature in the den can reach + 5-8 ° C. The she-bear slows down her metabolism, lowers her body temperature by several degrees, which allows her to significantly save energy.
Surprisingly, the bear's sleep is extremely sensitive, so the slightest movement above the den makes her open her eyes. From 2 to 4 cubs appear in the den, which feed on milk. A brown bear spends up to 5 months in a den. After leaving the den, the female spends some time near her winter refuge so that the cubs can develop muscles for long walks in the forest.
