Do bears really hibernate?
Some people believe that bears are not true hibernators. Squirrels, bats, rodents, marmots and other true hibernators enter a state close to suspended animation where body temperatures fall close to freezing and metabolisms slow almost to a halt.
A bear’s metabolism, heartbeat and respiration rate drops dramatically, but its body temperatures only drops about 12 degrees during hibernation. They don’t eat at all, nor do they go to the bathroom; bears’ dens are remarkably clean and odor-free … unlike true hibernators who wake up every few days to drink, go to the bathroom and nibble some stored food before going back to sleep.
A bear’s body is a model of recycling. While they’re hibernating, they recycle all of their waste products and actually heal any injuries they may have had when they turned in. So many scientists now call bears “Super Hibernators” because they can fall into a deep sleep for four to six months without eating or drinking, wake up in the spring and head back out into the world.
Why the Long Nap?
Bears don’t necessarily den up because it’s cold; they put themselves to sleep for the winter because food is in short supply. In far northern climates, bears might be in their dens fasting and living off their fat reserves for up to six months. In more temperate climates where natural foods are available longer, they may turn in anytime between November and mid-December, and emerge again in late March or early April.
Bears may den for much shorter periods of time and sleep less deeply if food (natural or human-provided) is available all year. In sub-tropical Florida only pregnant females den up for the short winter; other bears may turn in for just a week or two or not at all.
Life in the Den
Bears in their dens live off the fat reserves they worked so hard over the late summer and fall to acquire. Bears often change their position in the den and may even wander out into the world for brief periods and then go back to sleep. Hibernating mothers-to-be give birth in their dens, nurse their cubs and even clean up after the youngsters while they are “asleep,” something that many of you human mothers can probably relate to.
Never crawl into a bear den; bears wake up very quickly and can swiftly react to danger. And imagine how grumpy you’d be if someone interrupted your long winter’s nap.