Everyone knows that black bears hibernate during the cold winter months. They tuck away some time in December and keep hitting the snooze button until early spring. I was reading about some hibernating black bears in Brainerd, MN and decided to find out how they are able to sleep for such long periods of time.
It turns out that bear’s ability to hibernate for so long is a bit of a scientific mystery.
Many animals such as skunks, raccoons, and chipmunks also hibernate but in a much different manner than the black bear. The term hibernation used to be used by scientists to define a reduction in body temperature. The meaning of this term has changed solely from the wintering characteristics of our black bears.
All animals that hibernate have a major reduction in body temperature except for bears. Smaller animals that hibernate average a winter body temperature of 40 degrees Fahrenheit while bears average 88 degrees. This is only 12 degrees colder than their body temperatures in the summer.
Smaller animals must wake up every few days to increase their body temperature, and then they eat some stored food and pass wastes. Bears can stay asleep for up to seven months without eating, drinking, urinating, defecating, or exercising. They are even able to give birth while hibernating and this is actually very common. The cubs will nurse off of their mother all winter long until she is ready to get moving in the spring. I was very surprised to watch some videos on the Internet that showed the cubs being semi-active while the mother appears to be unconscious.
Bears use caves, downed trees, or even just semisheltered changes in landscape for a den and do not always return to the same den year after year. Some bears even switch dens many times throughout the winter months, while others wake up in the same exact place and position they lay down in seven months prior. It just depends on the bear and the location.
Bears can slow their heart rate down to eight beats per minute which allows their metabolism to decrease as much as 75 percent. Their heart beat averages 40-50 beats per minute in the summer. Scientists have related slower metabolism rates to falling body temperatures but this is not true with bears. The thick layers of body fat and increased fur allow them to stay warm while hibernating. They can put on as much as 30 pounds per week in the fall to get that storage of fat for the winter. It is no wonder they love digging through the garbage and eating everything in sight. I watched one pick up a deep fat fryer behind Trail Center years ago and actually drink all of the grease after a Friday night fish fry. It was running down both sides of her head while she licked it clean. Gross!
Many of the articles I read talked about the bears’ diet consisting of mainly berries and seeds with an occasional small animal or carcass during the early season. I have heard a few stories of bears taking our moose calves, which are very clumsy and vulnerable in the spring, allowing them to put on some quick calories after waking up.
There was no research to back this up, but I trust the sources that told me stories of witnessing this in the past.
Black bears can be very vicious if they want to be and they are excellent hunters. They have the nose of a canine, can charge at 30 miles per hour and are very proficient at climbing trees. Despite all of these impressive traits, they are rarely known to attack humans.
The National Center for Health Statistics claims that, “…for every one human killed by a black bear there are 60 people killed by domestic dogs, 180 people by bees, and 350 by lightning.”
This being said, the odds are pretty good that a bear is not going to attack you, but they are very protective of their young and should never be considered docile.
Cory Christianson, a graduate of the University of Iowa, has worked as a fishing guide on the Gunflint Trail since 2000. If you have any fishing reports or stories to share, send an email to: christiansoncory@hotmail.com or call 218-388-0315.
Leave a Reply