Bears are land mammals that live in different ecosystems around the world. They can live in forests, grasslands, and polar areas and are always at the top of the food chain. How much do you know about their habits and life cycle?
Bears are mammals that can reach between 1.3 and 2.8 meters in height and can weigh up to 500 kg. These considerable dimensions make them among the largest terrestrial animals in the world. Their appearance varies depending on the species, but they all have small ears and a short tail, a long snout, small eyes on a large head. The legs are short in proportion to the bust, but are extremely strong, armed with five fingers with curved claws.
In general, the bear does not stand out for sight and hearing, however, it is compensated by a very developed sense of smell which allows it to easily localize the preys.
The coat of the bears is long and abundant. The colors vary between brown, black and white. Besides, there are specimens with a curious appearance such as the Panda (Ailuropoda melanoleuca), with its two-colored snout, or the spectacled bear (Tremarctos ornatus), which has white circles around its eyes.
The phase in which they are sexually active is between 5 and 9 years when they reach sexual maturity. As soon as they are born, the puppies feed on mother's milk.
Which bears hibernate?
Bears are part of the circle of animals that hibernates in the winter months. However, this process is different from that of other animal species. Bears do not lose their ability to perceive the outside world when they are hibernating. In fact, they react to abrupt noises and sudden movements if someone bothers them.
It must be said, however, that not all species of bears hibernate. The panda, for example, who lives in China and Southeast Asia, does not need to, because his vegetarian diet of bamboo would prevent him from having the strength to deal with hibernation. Not even the spectacled bear hibernates because its food is available all year round, as is the case with the labiated bear (Melursus ursinus).
For its part, the Asian black bear (Ursus thibetanus) can hibernate or remain alert, depending on whether or not it has food in its habitat. The black bear (Ursus americanus) hibernates, but wakes up easily, which also happens in brown bears. Polar bears, on the other hand, always hibernate.
Why do bears hibernate?
Unlike other species that hibernate, bears do not always do so. If they have enough food available throughout the year and the weather conditions are good, they may decide not to hibernate.
Bears actually hibernate to make up for the lack of food and optimize their energy during the cold months. Most prey in winter are hibernating or scarce, trees lose their leaves and fruits, so feeding is difficult. Hibernation is a tactic for surviving these harsh seasons, as hibernation allows the bear to survive without ingesting food and burning far less energy than in the waking state.
For bears to hibernate, they must have previously accumulated a good amount of fat throughout the year. When they hibernate, their temperature decreases and their heart rate slows down, eventually, they will have lost about 40% of their initial weight.
Can a hibernating bear wake up?
Once the bear hibernates, it is still possible that it wakes up. These animals remain sensitive to external stimuli that they receive, so an abrupt sound or contact with another animal can easily wake them up.
It must be said that bears do not wake up during this long period to carry out their physiological needs. Their bodies have different microorganisms that feed on the substances contained in the feces and urine, transforming them into amino acids necessary for the body of the bear.
Hibernation of polar bears
Polar bears (Ursus maritinus) live in the iciest areas. They have a fur that protects them from extreme cold, under which there is black skin. They are among the most endangered bear species, as they are classified as "Vulnerable" by the International Union for the Conservation of Nature (IUCN). They have a life expectancy of 30 years, however, due to the destruction of their habitat, few are those who reach 18 years.
Polar bears hibernate in the coldest months when they seek natural shelters, such as caves or caverns, to preserve heat and be safe. Polar bear cubs can be born during hibernation and, thanks to their instinct, access their mother's milk to survive.