March 1, 2013

This winter has been bitter, windy, cold, slushy, icy and definitely snowy.  Considering all this, it is not surprising that many of us would like to sleep through it all and wake up when it is spring again, when the sun shines for hours and warm temperatures make going outside enjoyable.   Bears are a species that do just that—sleep through the winter and wake up in the spring.  While it is pretty well-known that bears hibernate for the winter, how much do you really know about their hibernation habits?

In the fall when the cooler weather begins, black bears start to prepare for winter hibernation by collecting rich foods in order to increase their fat for the months ahead.  Black bears add about 4 inches of fat and gain 2-3 pounds a day through their hunting and eating before winter.  When black bears are actually hibernating, their body temperatures decrease 10 – 12 degrees and their metabolic rate drops to about half of what it was.  Furthermore, black bears do not eat, discharge feces, or urinate while hibernating.  Additionally, female black bears typically birth and nurse 2-5 cubs that are born during the hibernation period.

Brown bears, often called grizzly bears in America, technically do not hibernate.  Grizzlies sleep through most of the winter season, but they are able to be awakened. In preparation for the winter when they will be sleeping and not eating, brown bears put on weight in order to survive.  Particularly in the far north, brown bears add up to 400 pounds of fat every summer!  A large female brown bear can get up to 770 pounds and a large male can weigh 1,300 pounds before winter.  As for nursing, between the months of January and March, up to four hairless cubs are born while the mother brown bear is sleeping.  Interestingly, some of the largest brown bears are found on the coast of Alaska, and especially in Kamchatka, located in the far east of Russia. In Russia, brown bears are not called grizzlies, but rather burii medved.

Here at the Minnesota Zoo, we have both black bears and brown bears.  The bears at the Zoo do not follow the normal winter behavioral patterns just described.  As Northern Trail Supervisor, Diana Weinhardt explains, “The [brown] bears go out every day on exhibit, because they are still fed every day, and asked to move, their winter habits have been modified from what they would be in the wild.” Visitors can explore the Medtronic Minnesota Trail to see the black bears and Russia’s Grizzly Coast to observe the brown bears all year long!