How Do Bears Survive the Winter? A Detailed Explanation of Bears' Overwintering Methods

Bears are the collective name for animals of the family Ursidae in the order Carnivora. Most live in forests, generally leading a solitary life, sleeping and resting during the day and being active and foraging at night. So, how do bears survive the winter?

1. How do bears survive the winter?

There are many kinds of bears, with 5 genera and 8 species, and different bears survive the winter in different ways. Some bears hibernate in winter, such as the brown bear. Some bears hibernate when they live in the cold north but do not hibernate when they live in the warm south, such as the American black bear and the Asian black bear. Some bears have the habit of partial hibernation, such as the polar bear. Some bears do not hibernate in winter, such as the giant panda, the spectacled bear, the sloth bear and the sun bear.

2. Bears that hibernate

1. Brown bear: It has the habit of hibernating, starting from the end of October or the beginning of November and lasting until March-April of the following year. During hibernation, its body temperature, heartbeat and detoxification system all stop functioning. In order to hibernate, it must eat 400-600 kg of berries and other food in autumn. As winter approaches, it begins to prepare a den, mostly choosing large tree hollows or rock crevices to live in, and lining the den with dry grass, leaves or moss. Before entering the den, it messes up its own tracks to prevent natural enemies from finding the den. During hibernation, if there is danger, it will wake up at any time.

2. American black bear: Bears in the northern regions have the habit of hibernating, for as long as 7 months; in the southern regions the hibernation period is shorter, and some even do not hibernate. In order to hibernate, black bears choose carrion and plant-based food in spring, and also catch some small game to supplement the fat consumed in winter; in summer they eat large amounts of berries, and in addition catch some rodents and other small prey to supplement nutrition; in autumn they enjoy all kinds of ripe delicious berries, fruits and nuts; in late autumn and early winter, they speed up feeding to prepare for hibernation. Before hibernation, they build dens in tree hollows, under logs or stones, by riverbanks, in caves, in hidden ditches and in shallow depressions. During hibernation, they store body fat and lower body temperature and heart rate to save energy.

3. Asian black bear: Black bears in the north have the habit of hibernating and come out of their dens to be active in March-April of the following year. In autumn they eat large amounts of food, mainly nuts rich in fat. Before hibernation, they build dens in tree hollows of large trees, rock caves and burrows, under logs or stones, by riverbanks, in hidden ditches and in shallow depressions. During hibernation, they lie dormant in the den, neither eating nor moving, in a semi-sleep state, and automatically lower body temperature and heart rate to save the body's metabolism.

3. Bears that partially hibernate

1. Polar bear: It has the habit of partial hibernation. In the severe winter, the polar bear's outdoor activity is greatly reduced, and it can go almost a long time without eating. At this time, it looks for a sheltered place, lies down on the ground and sleeps, its breathing rate decreases, and it enters partial hibernation. It only goes without food and water for a relatively long period, rather than the entire winter. During partial hibernation, the polar bear seems to sleep yet not sleep, and once it encounters an emergency it can immediately wake up and deal with the change.

4. Bears that do not hibernate

1. Giant panda: It is a species endemic to China, and its main existing habitat is the mountainous areas of Sichuan, Shaanxi and Gansu in China. It has a character of not fearing cold or damp and never hibernating. Even when the temperature is -4-14°C, they still move through bamboo thickets heavily weighed down by white snow. When mountain streams are frozen by ice, some giant pandas may, because they are attached to the concealed conditions and food base of their home, travel a long distance down along the gullies to drink water in the valleys and then return home. Giant pandas mostly feed mainly on bamboo leaves, and in winter they feed mainly on bamboo stems.

2. Spectacled bear: It is distributed only in South America and is a purely tropical animal. It does not need to hibernate, because the food sources in its living environment are abundant and do not run out all year round.

3. Sloth bear: It is mainly distributed in India and Sri Lanka, with a small distribution also in Bangladesh, Nepal and Bhutan. Because it lives in tropical regions, it does not hibernate, though it reduces activity when the rainy season arrives.

4. Sun bear: It is mainly distributed in Southeast Asia and South Asia, with a small distribution in Luchun, Yunnan and Mangkang, Tibet in China. This is the only bear that does not hibernate. Although they fear the cold, they do not hibernate, perhaps because they live in hot zones and food is relatively abundant all year round.