We can always tell when winter is coming on because of the preparations undertaken by Mama Bear and the year’s orphaned cubs in early fall.
Mama bear beds down.
Mama bear, looking pretty comfortable a few days before going to sleep for the winter. Usually the first bear to go into hibernation at Aspen every fall, she eventually covers the doorway with straw, hiding until spring.
First of all, their food intake increases dramatically because their bodies will live off the stored body fat.
By doing this, they don’t lose any muscle and can come out of their hibernation in the spring thinner but still quite strong.
Mama Bear is always the first to prepare her den. Staff provides the bears with boxes and plenty of straw so that they can shift it around as it suits them.
It takes a few days for each animal to get it just the way they want it, and we’ve seen in the past where several cubs will pile in together into one box.
Once it is arranged to their satisfaction, we won’t see them again until spring.
Hibernation is an adaptation to the climate in which animals live.
They can escape the necessity of having to find food during the harsh winter, and they don’t need to exert a lot of energy hunting and moving around.
Bears are actually not true hibernators, and can awaken quite suddenly if disturbed. Rather, they are in a deep sleep during winter, but have an active brain. Female bears even give birth and care for the cubs while denned up.
Other examples of hibernators include badgers, bats, chipmunks and groundhogs. Some of these wake up occasionally to eat some of their stored food, but soon return to sleep.
True hibernation occurs when an animal’s body temperature drops very low so that it almost matches the temperature outside; its heartbeat and breathing slow down as well and as a result the stored fat lasts longer, because the animal’s metabolic rate is much lower.
If there is a shortage of food in the fall, and it is unable to build up a fat deposit, the animal might not survive until spring.
An example of true hibernators is the groundhog.
They appear dead if disturbed. Its body temperature will drop to match that of the outside temperature and its heartbeat and breathing slow down too.
In this way they don’t need much energy and are able to live off their body fat.
It is therefore vitally important for these animals to find sufficient food in the fall so that they can survive the winter.
When you think of it, the adaptations that nature has provided for wildlife in order to survive even the harshest winters are marvellous. Humans have to cover up from head to toe and heat our homes in order to survive, but everything that wildlife needs is already there in their environment.
(These weekly articles are contributed by staff at the Aspen Valley Wildlife Sanctuary. The sanctuary rehabilitates orphaned and injured wildlife with a mandate to educate the public towards a better understanding of local fauna.)