Hibernating mammals throughout the Northland have either already emerged from their underground sleeping chambers or are about to very soon. Some of the true hibernators, such as chipmunks, thirteen-lined ground squirrels, and woodchucks might have taken a tentative peek outside, but decided against venturing out for good until the weather, such as it's been, becomes more spring-like.
Black bears, which are not considered true hibernators, will soon be ambling about the forests and woodlands in search for food. April is the month of awakening for Minnesota's American black bears. Having denned up several months ago -- sometimes as early as September or as late as November -- most black bears will have lost anywhere from 15 to 30 percent of their body weight by the time April rolls around.
Black bears are fascinating mammals that are fairly abundant across their range. And though sometimes becoming problematic for homeowners, farmers and apiarists, especially when natural foods are scarce, black bears -- sometimes called "black ghosts" of the forest -- are generally shy, elusive and rarely observed.
While polar bears have been known to reach weights of more than 2,000 pounds and brown bears well over 1,000 pounds, a 300-pound black bear is considered big. Even so, some male black bears routinely reach weights of 500 to 600 pounds. There are even records of 700 and 800 pound bruins.
As already mentioned, black bears are not true hibernators. In fact, while all bears do indeed sleep the winter away in a vegetative state with notable decreases in their vital signs, periodic arousal does occur. Moreover, female bears give birth to one to five cubs in January or February while "hibernating." The cubs nurse throughout the winter months as their mother sleeps.
During the months of rest, black bears do not eat, drink, urinate or defecate -- they survive solely on their fat reserves. Those reserves, which can amount to several inches thick inside their bodies, make up a substantial portion of a bear's overall weight. And because bears don't eat or drink during their winter snooze, little nitrogenous waste accumulates. Incredibly, a fecal "plug" in the rectum prevents defecation throughout their half-year slumber.
That withstanding, when black bears at last appear in the spring they will have lost a significant percentage of their bulk. Nursing females typically lose even more weight. It is for this reason that bears need to feed constantly on nutritional, high-protein and high-carbohydrate foods from early spring until late autumn. Their winter survival depends on it.
From April through the autumn months in woodlands across Minnesota, black bears will engage in a feeding binge of sorts. Bears need to gain as much weight as possible from now until when they den up once again. Carrion is an important springtime food, as are the first new shoots of grass and other succulent forage -- anything to maintain body weight.
However, as spring turns into summer and more diverse foods become available such as hazel nuts, acorns, berries, tubers, roots, herbs, grasses and sedges, black bears begin putting on weight and accumulating fat. Animal matter, such as ants, grubs, beetles, small mammals and white-tailed deer fawns, are also eaten. Even so, a black bear's diet generally consists of 75-percent plant material.
As summer wanes and fall approaches, weight-gains of up to 30 pounds per week are possible when good forage is available. When black bears do at last settle down for their long winter naps, a suitable den site is sought. In Minnesota a bear den is frequently inside small, excavated cavities within root masses of uprooted 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, in the middle of a cornfield or underneath a vacant summer cabin. There have even been a couple of documented cases where bears have used eagle nests as their winter dens.
Upon a bear's emergence come springtime, the whole cycle of putting on the pounds starts all over. Mating occurs in June through July and female black bears give birth seven or eight months later. The cubs are born very small, around eight ounces to a pound, and are blind, hairless, and helpless. They will remain with their mother for at least a year, usually two, while learning many important lessons of survival.
Black bears inspire many emotions to us human admirers. Bears possess remarkable senses, and, though growing large, are silent, quick and secretive. These extraordinary animals, powerful and intelligent as they are, are often misunderstood and needlessly feared. Just knowing that black bears exist throughout Minnesota's forestlands is our fortune as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org