Bears: Not Hibernators
Torpor versus Hibernation
What if I told you that you have been lied to for years? Well its true. Bears aren't hibernators they enter torpor instead. Torpor is the short-term reduction of body temperature (for bears, up to 100 days). Torpor is controlled by ambient temperature and food availability or, in a bear's case, energy stores. Torpor allows a bear to regain consciousness in a matter of seconds and be ready for action (running, attacking, eating, etc). For animals in hibernation, on the other hand, it may take hours to days, to gain back the energy they had before they began their long sleep.
How do Bears Survive During Torpor?
Bears prepare their dens well before they need them and rarely use the same den two years in a row. Once they settle down for the cold months, their bodily functions change greatly. The flow of blood becomes concentrated to the heart, lungs and brain. The bear is then further protected from the cold by their fur and up to four-inches of fat under the skin. The digestive system shuts down while asleep as no water or food is entering and waste is not exiting. The bear still needs sustenance every day consisting of water, protein and 4,000 calories. The animal’s energy stores provide this through its own metabolic system. Fat is broken down into calories and water, and muscle is broken down into protein and Nitrogen Urea. Nitrogen Urea is normally highly toxic in an animal’s system but a bear’s metabolic system recycles this through the liver and kidneys to produce amino acids. Those attach themselves to muscle tissue and are broken down into protein yet again.
What can Wake a Bear from Torpor?
A bear’s torpor is a lethargic state in which it can awaken from in just seconds. Loud noises such as trees falling, avalanche blasting caps or even a garbage truck can wake a bear from torpor. Here in Tahoe and Truckee we have bears that do not to enter torpor at all and roam our neighborhoods looking for food all winter long. Our civilization in their habitat has changed the way they expect food and thus changed their torpor and breeding patterns.
Warnings and Precautions
I have recently seen a few bears in a couple of neighborhoods in South Lake Tahoe and Stateline. At this time of year, they are desperately looking for a den and food. Remember to always put your trash in a secure location: bear box, your garage, or indoors. Remember also to double check that you have secured your doors and windows. As for wilderness areas, just be cautious. For those of you who go out and cut your own Christmas tree with a permit, be loud and aware in your surroundings to avoid surprising a bear. If you see a bear in a populated area this season don’t approach it; it is probably hungry and defensive. You can always call #911 in an emergency or the Tahoe Bear League 24/7, at (530) 525-7297. Also, visit their website to learn more about their amazing organization, http://www.savebears.org/.