Sweet dreams are bruin in the mountains as the region’s bears start scoping out places for their winter dens.
Bears really have only two seasons a year: hibernation’s coming and hibernation’s here, said Kim Annis, Montana Fish, Wildlife and Parks bear biologist in Libby.
They’ve been feeding in a frenzy known as “hyperphagia” for the past six or seven weeks, eating up to 20,000 calories and gaining several pounds, or more, a day, Annis said, noting that adult bears in a good huckleberry crop can pile on more than 100 pounds before denning.
“This was a good berry year in the Cabinet-Yaak and southern Rocky Mountains and not so good in the Northern Rockies along the Eastern Front. Fruits, grasses, forbes and meat, usually the remains of hunter-killed animals, are also central to a bear’s fall diet.”
This rush to put on fat is what tempts bears to score calories in orchards that haven’t been cleared of fruit, or where livestock feed, dog food, bird seed, garbage and other foods are left outdoors and accessible.
“Bears den up when winter begins in earnest and their natural foods disappear—sometime between October and December, Annis said.
Grizzlies generally prefer to den at elevations at or above 6,000 feet. “They use their long front claws and powerful front legs to dig a den in the ground, usually selecting remote areas where the snow will be deepest,” Annis said.
“Black bears typically den at much lower elevations and often use ready-made dens within tree cavities, burrows, and rock-crevices with openings that are just large enough for a bear to squeeze through. Last fall a black bear near the Kootenai River created fine den under an old log jam along a stream.”
To minimize heat loss, bear’s choose small dens with just enough room to turn around in. “While a black bear will reuse a ready-made den, grizzly bears typically dig new dens, even though they may den in the same area as in winters past,” Annis said.
Bears do not eat, drink, exercise or excrete any body wastes during their five- to six-month slumber. “They are uniquely able to convert toxic body wastes, and break down muscle and organ tissue to supply protein,” Annis said. “Their fat breaks down to supply water and calories. Amazingly, a bear’s muscle mass and tissues do not atrophy in this process.”
“Adult male bears den just as they spend most of their lives, alone.
“Female grizzly bears and their offspring typically den together for three winters: the winter the cubs were born and two consecutive winters after that. The female separates herself from her offspring when they are two and a half years old and she is ready to breed again.”