The Case of the Hungry Black Bear
From autumn's feeding frenzy to spring emergence , follow Michigan's black bears through their yearly cycle. Discover how they prepare for winter.
Michigan is home to nearly 12,000 black bears. About 10,000 live in the Upper Peninsula, while the rest roam the Lower Peninsula, mostly in its northern half.
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As summer begins to fade into fall, Michigan’s black bears enter a remarkable season of their own. Starting around August, they experience hyperphagia, a period of intense, almost nonstop feeding. With winter on the horizon, bears may spend up to 20 hours a day searching for food, consuming as many as 30,000 calories in a single day. Nearly anything is on the menu: nuts and seeds, fruits and berries, insects, and even small animals, living or dead. Every meal helps prepare them for the long months ahead.
By November, the frantic pace begins to slow. Bears retreat into dens, finding shelter in places like hollow logs, brush piles, and rocky crevices. But what happens next isn't quite the deep hibernation we often imagine.
Black bears enter a special form of winter sleep called torpor. Their heart rates drop from around 50 beats per minute to fewer than 20, while their body temperatures fall only slightly, remaining between 88 and 98°F. For months, they go without eating, drinking, urinating, or defecating. Instead, their bodies have a remarkable way of recycling waste proteins and urea into usable amino acids, helping them preserve muscle and conserve resources through the winter.
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Deep inside these quiet dens, another chapter of the bear's winter story unfolds. In January or early February, pregnant females awaken from torpor long enough to give birth to one to three cubs. Tiny and helpless, the newborns weigh less than half a pound. Their eyes are closed, and their bodies are nearly hairless. They spend their first weeks nestled against their mother, feeding on her rich milk.
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By late March or April, the forest begins to stir. Michigan's black bears emerge from their dens, often with their new cubs close behind, and begin the search for food all over again. Leftover nuts and berries, tender green plants, and carrion offer some early nourishment, but natural food can be scarce. That's when a bear might wander toward a bird feeder, tip over a trash can, or discover a dish of pet food left outside. After a long winter, an easy meal can be hard to resist.
