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May 2000
Humans have had a long association with bears. Early, very early in the development of humans, before we were herders and planters, we were hunters. In northern climates all over the world, bear was an important game animal, providing humans with meat to eat and skins for warmth. Later cultures, no longer dependent on bears for survival, still had bear celebrations, often held in the spring. A vestige of these holidays may be the feast day, on April 13 in Britain, for St. Ursus, whose name is Latin for "bear."
In Maine we have the species black bear. About twenty-two thousand individuals, more than any other eastern state, roam over eighty-five percent of the state. Maine's extensive moist deciduous-coniferous forests, bears' preferred habitat, offer abundant food sources, cover, and adequate water. They use every layer of the vertical forest structure, for example digging in the earth for grubs, foraging for berries in the shrub layer, and climbing trees to the canopy layer to eat tree buds, acorns and beechnuts.
To escape from winter weather, black bears locate their den sites under fallen trees, in hollow logs, under rock ledges or other protected areas. Black bears den in the fall, earlier or later depending on the availability of food such as beechnuts. In northern Maine forests, where there are no apple or agricultural crops to compensate for a year with a small crop of beechnuts, bears usually go into their dens by mid-October. In southern Maine, they den by mid-November or the beginning of December.
Black bears go into a deep winter sleep, not a true hibernation, which is also called torpor. During this period, their core body temperature is reduced only ten degrees, but their respiratory and heart rates are greatly slowed. In this state, they maximize their bodies' efficiency in metabolizing stored calories from their body fat. They spend five or six months in the dens each winter.
A female bear has cubs once every two years, during January or February. Those females who have cubs are somewhat active and alert while in their dens because they have as many as four cubs that are nursing, nudging and certainly not in a deep sleep. The mother bear leads the cubs away from the den in mid to late April. Male bears and non-bearing females also emerge from their dens about this time.
Spring food sources include greening grasses, forbs, and buds and leaves of woody plants. Animal matter, including insects and vertebrates, is rich in protein and fat and so is an important food for the bears. They eat colonial insects, such as ants, beetles and bees. They eat carrion and, although not considered active predators, in the spring they will prey on young deer and moose.
In summer, berries and fruits, called soft mast, are the primary food sources. In fall, acorns, beechnuts and hazelnuts, called hard mast, are the major foods and provide the body fat to sustain survival through the winter in the den. Bears also use agricultural crops, such as apples, blueberries, oats and corn, especially when natural foods fail. As long as food sources are close to escape cover, forest with undergrowth, bears will exploit a food source. When forestland is too fragmented by clearings and development, bears will not be present.
The quality of habitat, and especially food sources, has much to do with the population dynamics of black bears. In Maine, half of newborn cubs die, usually because of starvation. By the time an individual is two years old, its chance of survival is greater than ninety per cent and it may live for thirty years.
Craig McLaughlin, the wildlife biologist with Inland Fisheries and Wildlife who focuses on black bears, has a web site, the Maine Black Bear Study, at http://janus.state.me.us/ifw/wildlife/bear/ecology.htm. Linked to this are other bear topics including "Living with Bears." Black bears are an intelligent and adaptable species. We are lucky that they are part of Maine's ecosystem, and I understand the reasons for celebrating bears.
By Nancy Coverstone (ncstone@umext.maine.edu), University of Maine Extension Educator in Androscoggin and Sagadahoc Counties
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