Since prehistoric times when animal worship gave rise to the Cult of the Bear, human beings have variously revered, tamed, feared and hunted bears. The black bear is common throughout most of North America – a fact that makes its scientific name, Ursus americanus, easy to remember. But in spite of man’s interest in bears generally, and the wide distribution of the black bear specifically, serious scientific study of this particular species did not begin until about 25 years ago. In Ontario, the black bear’s value as game was ignored until 1961, when the bounty was lifted and it was declared a game species.
The black bear inhabits most of the forested areas of North America, from Mexico to Alaska. It is not found in the southwest and the extreme north.
Black bears vary considerably in weight, depending on their age and sex and the season. Because of their bulky appearance, their weight is often over-estimated. Some individuals of up to 360 kg (792 lbs) have been found, but adult males average 113 kg (250 lbs), and adult females average 63 kg (140 lbs). Most male and female cubs weigh between 14 and 22 kg (31 and 48 lbs) by mid autumn. A year later, females average approximately 20 kg (44 lbs), and males, approximately 24 kg (53 lbs). This suggests that growth is slow during the bear’s first year on its own. Most of their growing is done between the ages of three and five. Females are usually full grown by the age of five, while males may continue to grow even after the age of seven. Among the adaptations of the black bear is its ability to grasp with its front paws. Although adults climb trees less often than cubs, this skill is retained throughout the black bear’s life. Black bears shed and replace their footpads during the denning period.
The black bear has one of the lowest reproduction rates of the North American land mammals, usually breeding only in alternate years. Sexual maturity generally occurs by the age of three or four, but in some areas it may not occur until the age of five or six. The fertilized egg does not become implanted for several months after mating, and may not implant at all, if the summer food supplies are low and the female is unable to accumulate enough fat reserves to produce and feed young. Mating takes place from June to early August, and the peak period is between mid June and mid-July. If implantation occurs, the cubs are born during late January while the mother is still in her winter den. Litter size varies from one to four, and litters of two or three are most common. New-born cubs weigh about 0.2 to 0.3 kg (6 to 9 oz) which is only one two-hundredth of their mother’s weight. Within two months they increase their weight by 1,000 percent on the rich milk supplied by their mother. The cubs climb trees easily at this age, and will remain near them for security until about mid-summer, when they are as likely to run from danger as to climb. The young remain with their mother until they are about 16 months old, by which time she is ready to mate again. The females may stay on part of their mother’s home range until she dies, when one of them can take over her territory. Young females, with no territory of their own, apparently do not breed. The male offspring may remain on the mother’s range during the first year of independence, and often disperse between their second and fourth years. Black bears may live from seven to fifteen years in the wild. The males are more vulnerable to hunting and trapping because they travel more widely, and therefore have a shorter average life span than the adult females.
The black bear appears to show a reluctance to venture very far from trees, which it may associate with protection from danger. It is seldom found in very open terrain. Favourite den sites are the bases of fallen trees and beneath roots. The dens are not much larger than the bears themselves, and are lined with leaves and grasses. Maternity dens often contain alcoves for cubs. Sometimes, the forest floor within 12m (39 ft) of the dens is cleared of leaves.
Food and Feeding Behaviour
Choice feeding spots of the black bear include forest edges, dumps and meadows as long as there are trees nearby. A true omnivore, the bear varies its diet according to what the season has to offer. In early spring, it eats newly emerging grasses and sedges as well as ants and other insects. The leaves of trembling aspen form a large part of the diet between May and mid-July. By mid-July, good supplies of strawberries, serviceberries, pin cherries and blueberries allow the bear to put on weight. As the season progresses, insects, like wasps and bees, are eaten in increasing amounts. The black bear eats mammals when the opportunity arises, but studies of bear scats indicate that most mammal meat is consumed as carrion. There seem to be few cases of actual predation.
Contrary to popular belief, black bears are not nocturnal animals, but have a major rest period at night. They are usually active between 5 a.m. and midnight, and take a short rest of one or two hours in the early afternoon. During the summer, they are active for three-quarters of the day. A curious animal, the bear routinely inspects everything it finds in its travels and its inspections are not limited to potential food sources. Most adult females have a specific range in which they mate, den and rear their offspring. These ranges are maintained until they die, but are not necessarily exclusive. The home range size of the female is from 20 to 50 square km (8 to 20 square mi). Males travel more widely and their ranges are difficult to determine. However, male ranges are known to encompass several female ranges. Except during the mating season and after cubs are born, black bears are solitary. There is a close bond between the female and her cubs. Between the mid-April emergence from the winter den and the coming-of-age of the offspring, the family unit remains in a preferred spot. This home-site is dominated by a large “escape” or “sanctuary” tree, often located on the edge of a swamp. Here, the combination of a closed canopy and damp moss provides the group with a cool retreat. Denning usually takes place between mid-October and early November. Females with cubs den earlier than lone females, and males seem to den later. Some bears use a surface den, a lined depression in the ground beneath a tree, for two or three weeks before entering the winter den.
Except for the mortality caused by human activity, the adult black bears in the Ontario regions studied so far have been found to have a high rate of survival. Like other mammals, black bears appear to be more numerous in some years than in others. Although their numbers do vary, it is often a change in behaviour rather than in population size that accounts for increased sightings. When food is scarce, the animals become more visible as they emerge from seclusion to seek other sources of food at such times, conflict between people and bears also increase. Frequently, what is thought to be an outbreak of black bears is actually related to a late spring frost, which reduces the food supply.
Since bear populations cannot withstand the pressures of unlimited harvesting the major challenge to wildlife managers is to maintain a population sufficient to permit harvesting, and at the same time to reduce the number of conflicts between people and bears in settled areas. The number of adult females in the harvest can gauge the pressure on the bear population. Females are very territorial and less vulnerable to hunters and trappers. Thus, a large percentage of females in the harvest clearly indicates that the pressure on the population is too great and must be lessened. Trapping accounts for a very small proportion and, of those bears trapped, most are nuisance animals that are removed from garbage dumps and bee-keeping establishments.