How Long Do Bears Hibernate?

What is Hibernation?

Hibernation is when animals (or plants) spend the winter in a dormant state. They spend several weeks or months sleeping, and this state of inactivity helps them to conserve energy. Hibernation is characterized by slow breathing, a slow heart rate, low body temperatures, and a low metabolic rate. Typically, animals hibernate to cope with months that are low in food supply. Stored body fat from earlier months gives the body all the energy it needs to last the hibernation period.

Do Bears Hibernate?

When discussing hibernation, the first animal that comes to mind for most people is a bear. However, there is some debate about whether bears actually hibernate. First, hibernation is defined as the animal’s body temperature drops to match the outside temperature. This is not the case for bears. A bear’s breathing and heart will slow, but their body temperatures remain quite high in comparison.

Another key difference is waking up from hibernation. Most animals that hibernate, like squirrels, wake up gradually. However, bears can wake up instantly from their deep sleep.

Due to these differences, some people argue that bears do not truly hibernate. Instead, they use distinct terms for what bears do such as winter sleep, carnivoran lethargy, torpor, and dormancy. Still, it is widely accepted by physiologists to label bears as hibernators.

How Long Do Bears Hibernate

Different species of bears hibernate for slightly different lengths of time, based mostly on their climate.

Black bears can hibernate for up to seven and a half months without drinking water, eating food or defecating.

Grizzly bears typically hibernate between five to seven months.

Mexican Black Bears usually do not hibernate at all or will hibernate for just a few weeks out of the year. Due to a warm environment, hibernation is not necessary for these bears.

Alaskan Brown Bears can hibernate from five to eight months. As Alaskan Brown Bears are found in a colder climate, they typically spend a long time in hibernation compared to other bear species.

Why Do Bears Come Out of Hibernation

Bears naturally come out of their state of hibernation when the weather turns warmer. Changing weather patterns around the world can bring bears out of hibernation earlier. This can possibly have damaging effects on local bear populations if their food cycle does not continue to match up with the weather. If plants have not started to grow, but bears are waking up, they can become starved for food, making them more susceptible to illness.

Additionally, bears that wake up earlier increase their chances of running into humans. Typically, National Parks and local municipalities keep track of regular bear schedules and can advise the public when bears usually become active in their area. If these patterns are drastically changing, local populations may not be aware. This is unsafe for both parties: the humans and the bears.

Bears can also come out of hibernation if they are disturbed. As previously mentioned, unlike other animals, bears do not slowly awaken from hibernation. So, if disturbed by loud noises or approaching danger, they can immediately wake up to defend themselves or their cubs.