One of the most fascinating abilities that the bears of North America have is that of being able to hibernate. In this blog and video, we’ll take a look at the bears of Alaska as an example and I’ll answer many common questions such as: “What is hibernation? How does hibernation work? Why do bears hibernate? When do bears hibernate? How long do bears hibernate for? And, when do bears come out of hibernation?” If you hang around till the end of the video, you’ll also learn the answer to another popular question, and that is, “Do polar bears hibernate?”
The bears of North America have varying degrees of hibernation behavior based on their particular species as well as their location. In order to simplify things a bit for this video, we’ll be looking specifically at the bears of Alaska, including the American black bear, the grizzly bears of the interior, the coastal brown bears, including the mighty Kodiak bear, and the polar bear.
What is Hibernation and Why do Bears Hibernate?
Hibernation is an amazing phenomenon in which bears can sleep for up to eight months without eating, drinking, or going to the bathroom. But what’s even more amazing is that when bears wake up from this long winter nap, they don’t show any major signs of deterioration. While they do lose a significant amount of fat during hibernation, they lose very little muscle and bone mass and they don’t have any significant buildup of toxins in their bloodstream, as they recycle their own waste in order to maintain their muscle and organ tissue.
After packing on an incredible amount of fat during the summer and fall, bears instinctually go into hibernation as a means of surviving the cold, desolate winter months when little to no food is available. When it’s time to hibernate, bears dig a winter den, which is essentially a big hole in the ground, and go into a state of dormancy. Their body temperature only drops slightly, but their respiratory and heart rate drops dramatically, averaging only one breath and 8 to 10 heartbeats per minute.
Even though a bear’s bodily functions slow down dramatically during hibernation, surviving the harsh winter months still takes a lot of calories. Bears can burn up to 4000 calories a day during hibernation, which is why it’s essential for them to put on as much fat as possible during the summer and fall, as their body fat is metabolized into the water and food they need for survival.
When do Bears Hibernate?
The exact time that the bears of Alaska go into hibernation can vary a little depending on location, with the bears of the colder, northern regions starting a little earlier, and the bears of the warmer, southern areas going into hibernation a little later, but in general, most bears will start heading to their winter dens in October.
How Long do Bears Hibernate?
Again, this depends on location. The bears of the northern regions of Alaska typically hibernate for 6 to 7 months, while the bears of the south will hibernate for 2 to 5 months, with a longer hibernation time for sows and newborn cubs. Not all bears hibernate the entire time, however. Some bears will leave their den if it becomes flooded or damaged, or, if an abundant food source becomes available. In fact, in areas with available winter food sources, either natural food or human-related food such as trash, some bears will delay hibernation, or not hibernate at all.
Do Polar Bears Hibernate?
Polar bears in general do not hibernate in the same manner that black and brown bears do. Male polar bears and females that are not pregnant remain active during the winter months. Expecting mother polar bears do, however, enter a den for the winter to have a safe place to give birth to their young. While expecting mothers rely on their accumulated body fat to survive the winter in their den, their heart rate, respiratory rate, and body temperature do not decrease nearly as drastically as hibernating brown and black bears do. This helps to ensure that her cubs will stay warm and survive.
Watch the video below to see more!