Black bears live in the shadows
Common, yet rarely observed, few species of Minnesota's mammals are as revered as they are feared as the American black bear. Though keeping mostly to themselves, these "black ghosts of the forest" are the most abundant and widely distributed of the three species of bears that inhabit our continent.
Interestingly, black bears aren't necessarily always black in color. Their pelage varies in color that can range from black to brown and to beige, red/cinnamon, and even white. They often have a small patch of white fur on their chests. Preferring the dark and dense understory that mixed coniferous-deciduous woodlands offer, nature has provided the American black bear with the ultimate in camouflage: Black bears are creatures of the shadows.
The black bear is the smallest species of North American bear. While polar bears have been know to reach weights of over 2,000 pounds and brown/grizzly bears well over a thousand, a 300 pound black bear is considered large. Even so, some male black bears routinely reach weights of 500 to 600 pounds. Seven hundred and 800 pound bruins are also on record.
Black bears are not true hibernators. Mammals such as ground squirrels, woodchucks, and chipmunks are animals that enter true states of hibernation. These rodents' heart rate, body temperature, and metabolism slow to levels that barely maintain life.
Black bears, on the other hand, sleep in a less vegetative state, their vital signs decreasing much less drastically. Periodic arousal from slumber, however, is common. In fact, female bears give birth while "hibernating." The cubs nurse throughout the winter months and after they emerge from the den. They learn to feed on plant and animal matter soon after. Litter sizes range from one to five cubs, with two being the average.
During the months of rest, black bears survive on fat reserves and do not urinate or defecate. Because bears do not eat or drink during their lethargy, little nitrogenous waste accumulates. A fecal "plug" in the rectum prevents defecation. Those fat reserves, which can amount to several inches thick inside bears' bodies, make up a substantial portion of their overall weight. That withstanding, black bears emerging in the spring have commonly lost 15 to 30 percent of their bulk. Nursing females typically lose even more weight. It is for this reason that bears need to feed constantly throughout the season-of-plenty and that those foods consumed are of highest nutritional value.
Right now, in woodlands across Minnesota, black bears are on a feeding binge.
Bears need to gain as much weight as possible from now until den-up. Hazel nuts, acorns, berries of all kinds, tubers, roots, herbs, grasses, and sedges are just some of the many items on the menu. Indeed, the diet of black bears is primarily plant material; up to 75 percent. Animal matter, such as ants, grubs, beetles, small mammals, white-tailed deer fawns, and carrion are also eaten.
But now is also the time when human and bear encounters increase. Black bears, led by their noses and insatiable appetites, sometimes wind up in bee hives, backyard bird feeders, garbage receptacles, and even towns and cities.
I've seen bears lick moths off my home's windows, pull hummingbird feeders down to drink the juice, and have watched them contentedly lap up sunflower seeds from birdfeeders. The drive to eat is paramount in the daily and nightly activities of all black bears. Weight gains of up to 30 pounds per week are possible when good forage is available. Interestingly, when beehives are targeted, it's not so much the honey that the bears are after but, rather, the protein-packed larvae.
When black bears do at last settle down for their long naps, usually in late October and November, a suitable den site is sought. Quite often it's inside small, excavated cavities within the roots and soil of felled trees, or in brush piles, hollow logs or trees. And sometimes all that's required is a makeshift nest underneath the boughs of a spruce or fir tree.
Whatever the den becomes, it isn't usually until early spring that a bear will be up and around again. In my work as a wildlife biologist, I've seen firsthand the wide variety of dens that black bears use or create. From underground dens to high spots in a cattail marsh, black bears are either methodical and very selective in den selection or they're spontaneous and indiscriminate in their selection of den sites.
Upon emergence, the whole cycle of putting on the pounds starts over. Mating occurs in June through July and female black bears give birth some seven or eight months later. The cubs are born small (from eight ounces to a pound), blind, hairless, and helpless and will remain with their mother for a year or two, learning from her the important lessons of survival.
What with the awe that black bears inspire, it is difficult to understand why this impressive animal was bypassed in favor of a ground squirrel as Minnesota's state mammal. Incredible senses; silent, quick and secretive; and powerful and intelligent, indeed, our fortune is knowing that the American black bear lives among us, as we get out and enjoy the great outdoors.