Hibernation of she-bears is a unique mechanism of adaptation to severe weather conditions of the taiga wood. Stay in a den allows she-bears not to care for livelihood in the coldest season and to bring forth offspring in rather protected conditions.
How it is slept in a den to a polar she-bear?
Hibernation for she-bears is a special period as at this time the animal not only waits the coldest season when the amount of food sharply decreases, but also gets posterity. There is an opinion that bears of all types regardless of a floor fall into hibernation, but it far not so. For example, white bears males do not fall into hibernation, and spend the whole winter on ice, actively hunting and acquiring fat by forthcoming summer.
However white she-bears are forced to fall into hibernation and need of production of posterity is the reason for that. In environmental conditions of dwelling of polar bears the considerable layer of fat which newborns do not have is necessary for survival. For this reason white she-bears do big dens in which temperature never falls below 0th °C in snowdrifts. Thus, the bear cubs warmed by heat of mother can gain weight, eating fat milk. In a den the polar she-bears spend about 6 months that bear cubs could get stronger enough for life in the frozen world where ice around reigns.
Wintering of a brown she-bear
Brown bears fall into hibernation irrespective of a floor, but nevertheless females of this look have the unique features. She-bears bring forth offspring in a den, but to acquire fat, they need to seize all opportunities in respect of food which are available in the summer. Females of bears copulate in the early spring, but at the same time are capable to postpone pregnancy approach. Thus, they time that bear cubs appeared in the den protected from predators.
She-bears prefer to equip dens not in cold snow, and under big snags of century trees or in specially dug cavities in ravines. Temperature in a den can reach +5-8 °C. She-bear slows down the metabolism, reduces body temperature by several degrees that allows it to save energy significantly. Surprisingly, but the dream of a she-bear is extremely sensitive therefore the slightest movement over a den forces it to open eyes. In a den there are from 2 to 4 bear cubs who are fed with milk. The brown she-bear spends up to 5 months in a den. After an exit from a den the female spends some time near the winter shelter that bear cubs could develop muscles for long walks on a forest thicket.