How long can you stay in bed? The average person sleeps 9 hours a day, the average dog sleeps 11 hours a day, and the average cat sleeps 16 hours a day. Bears usually hibernate for 7 months! However, hibernation is very different from sleep. During hibernation, the animal’s metabolic rate, heart rate, and respiration rate are greatly slowed down. Hibernation occurs in many species of animals, including bears, various ground squirrels, marmots, some prairie dogs, fat-tailed pygmy lemurs, and others. Hibernation has been well studied in bear species, but scientists debate whether this behavior of bears is “real” hibernation. In this article, we explore bear hibernation, whether it is “real” hibernation, and where different species of bears hibernate! What, why, when and where – let’s find out!
What is hibernation?
In short, hibernation is when an animal uses less energy for extended periods of time.
Now let’s dive into the details. Hibernation is a state of physiological rest and metabolic depression, usually in response to cold temperatures or lack of food. To break this, hibernation is when the animal becomes inactive and its internal processes work slower in order to use less energy. During hibernation, the animal’s metabolic rate is greatly reduced. Metabolic rate describes the amount of energy used by all human cells and is usually measured in terms of oxygen consumption over time. Consequently, a decrease in metabolic rate is associated with a decrease in respiratory rate and heart rate. Endotherm is an animal that regulates its body temperature through metabolic processes. A decrease in metabolic rate conserves energy and causes a decrease in body temperature.
During the winter months food is often scarce and may not be sufficient for an awake animal trying to forage or hunting, and wasting energy that it cannot replenish. During times of food shortages, many animals eat large amounts of food when they eat. Then, when there is no food, they hibernate. Excessive overeating before hibernation is called hyperphagia. Hyperphagia is necessary before the hibernation period because it is necessary to establish sufficient energy reserves to keep the animal in the hibernation period.
The original definition of “true” hibernation was a decrease in metabolic processes that lead to a significant decrease in body temperature. Bears’ body temperature drops by only 3-5ºC compared to other animals, whose body temperature drops by 32ºC or more. Therefore, scientists were not sure if the bears really hibernate. Recent studies have shown that many bears hibernate and do not go into any other state.
Why do bears hibernate?
Not all bears hibernate. For example, polar bears are active all year round and have the unique ability to starve for months when food is scarce. Panda bears also do not hibernate because they can move to higher and lower altitudes when the ambient temperature changes. Likewise, the sun bear does not hibernate because its food resources are available at any time of the year.
Bears that hibernate hibernate because seasonal changes in food availability make them unable to support themselves for long periods of time. Even the omnivorous brown bear, which feeds on both meat and plant resources, hibernates during the winter months. Many plant food resources lose their fruits and foliage in severe winters. The prey also becomes more ghostly and can also hibernate. The lack of food available requires certain species to go into an inactive state in which their metabolism slows down. This is so that they can stretch their available resources over longer periods.
When do bears hibernate?
Bears that hibernate include the Andean bear (also known as spectacled bear), the American black bear, some Asian black bears (also known as moon bears), and brown bears. These species hibernate on signals from the environment. A 2016 study tracked the hibernation cycles of 14 brown bears over three winters to better understand how this happens. Bears have been found to hibernate in their dens when they first look at snow and when temperatures reach 0ºC. However, their body temperature, activity level, and heart rate begin to drop a few weeks before.
In the period before hibernation, these species of bears are hyperphagic in terms of accumulating reserves of nutrients and energy. The American black bear eats up to 90 pounds of food a day in preparation for hibernation. Brown bears also weigh the most in the late fall before winter. Himalayan black bears usually weigh between 200 and 265 pounds, but can weigh up to 400 pounds when gorged ahead of winter.
Some bear species, including American black bears, hibernate during pregnancy. Almost all pregnant Asiatic black bears hibernate as well. Mothers gain significant weight before they hibernate, and pregnancy occurs while they are asleep. The offspring are born either during or shortly after the hibernation period. The health and weight of the offspring is a direct reflection of how much weight the mother might have gained before hibernating.
Where do bears hibernate?
Bears hibernate in dens they find or build to protect themselves from the elements while they sleep. American black bears usually burrow in the ground. They can also take refuge in hollowed-out tree holes, under logs, or in caves. It has been observed that female black bears are more selective in den choice than males. Many Asiatic black bears remain active throughout the year, but some northern subspecies winter seasonally. Usually they prepare dens similar to American black bears. These include caves, hollowed out logs, holes they dug in the ground, or abandoned burrows of other bears. Likewise, brown bears usually make holes from hollow logs, cavernous tree roots, holes in the ground, or caves.
Although polar bears do not hibernate, they create burrows for pregnant women and enter a dormant state that bears some resemblance to hibernation. A pregnant female digs a maternity hospital in a snowdrift, which consists of an entrance tunnel and three chambers. She then goes into a dormant state, similar to hibernation. However, this state is not continuous sleep, and her body temperature does not drop. The bear’s pulse is reduced from 46 to 27 beats per minute. She remains in this den even after the birth of her offspring for the period of breastfeeding. Cubs are born weighing 2 pounds, and when the mother opens the entrance to the den, they weigh 22-33 pounds! Polar bears in the same subpopulation often reuse maternity hospitals.
How are different types of bears doing today?
Different types of bears have different conservation status – from least hazardous to vulnerable. Bear species for which the status is least dangerous include the brown bear and the American black bear. The IUCN Red List tracks these populations and reports that the brown bear populations are stable and the American black bear populations are growing.
Vulnerable bear species include sloth bear, sun bear, spectacled bear, polar bear, Asiatic black bear, and giant panda. The vulnerable species is at risk of becoming endangered if there is no intervention. All of these vulnerable species are declining, with the exception of the giant panda.
In 1990, 1994, 1996 and 2008, panda bears were listed as endangered on the Red List. Successful conservation efforts led to the reclassification of pandas from endangered to vulnerable in 2016. Conservation efforts include the identification of protected national parks, breeding programs, and protective legislation. Roughly 70 national reserves collectively formed the Giant Panda National Park in 2020. Its goal is to improve the availability of mates for disparate populations of pandas. The area of this national park is 10,500 square miles, which is three times the area of Yellowstone National Park.th the largest of 423 parcels in the US National Park System.