Even members of the same species, like black bears, differ in their approaches to overwintering, depending on where they live.
In eastern North America, food sources like nuts and berries stay available longer, so black bears in places like New York and New Jersey don’t start hibernating until November or December. But in the southwestern United States, where food sources get scarce earlier, bears can spend as long as six or seven months a year—more than half their lives!—in hibernation.
Before they settle in for a long winter rest, black bears spend the summer and fall in a state known as hyperphagia, chowing down on just about anything they can get their paws on.
“During this period, a bear will eat and eat and eat, all day long,” says Rae Wynn Grant, Doris Duke Conservation Fellow in the Museum’s Center for Biodiversity and Conservation and an educator in the Science Research Mentoring Program.
Once they’re feeling full enough, bears have to find a place to turn in for the season. Caves or hollowed-out logs are classic bear beds, but just as often, the animals will simply find an overhang under which to spend a few months. One must-have for a hibernation location, says Wynn Grant, is a nearby water source, to ensure that the animal can have a drink as soon as it wakes up.
Once they’re tucked in, bears don’t get up for anything. Waste products like urine are recycled back into their bodies to keep them hydrated. And newborn black bears arrive in the world, amazingly, without disturbing their mom’s slumber. Tiny newborn bears find a nipple, settle in, and suckle until spring, when mama bear and cubs emerge from their den together.
To learn more about black bears and how they hibernate, watch Rae Wynn Grant discuss the subject next to the black bear diorama in the Museum’s Bernard Family Hall of North American Mammals.