Category: Bears

Black Bear General Biology and Behavior

Black bears typically are nocturnal, although occasionally they are active during the day. In the South, black bears tend to be active year-round; but in northern areas, black bears undergo a period of semihibernation during winter. Bears spend this period of dormancy in dens, such as hollow logs, windfalls, brush piles, caves, and holes dug into the ground. Bears in northern areas may remain in their dens for 5 to 7 months, foregoing food, water, and elimination. Most cubs are born between late December and early February, while the female is still denning.

Black bears breed during the summer months, usually in late June or early July. Males travel extensively in search of receptive females. Both sexes are promiscuous. Fighting occurs between rival males as well as between males and unreceptive females. Dominant females may suppress the breeding activities of subordinate females. After mating, the fertilized egg does not implant immediately, but remains unattached in the uterus until fall. Females in good condition will usually produce 2 or 3 cubs that weigh 7 to 12 ounces (198 to 340 g) at birth.

After giving birth, the sow may continue her winter sleep while the cubs are awake and nursing. Lactating females do not come into estrus, so females generally breed only every other year. Parental care is solely the female’s responsibility. Males will kill and eat cubs if they have the opportunity. Cubs are weaned in late summer but usually remain close to the female throughout their first year. This social unit breaks up when the female comes into her next estrus. After the breeding season, the female and her yearlings may travel together for a few weeks. Black bears become sexually mature at approximately 3 1/2 years of age, but some females may not breed until their fourth year or later.

In North America, black bear densities range from 0.3 to 3.4 bears per square mile (0.1 to 1.3 bears/km2). Densities are highest in the Pacific Northwest because of the high diversity of habitats and long foraging season. The home range of black bears is dependent on the type and quality of the habitat and the sex and age of the bear. In mountainous regions, bears encounter a variety of habitats by moving up or down in elevation. Where the terrain is flatter, bears typically range more widely in search of food, water, cover, and space. Most adult females have well-defined home ranges that vary from 6 to 19 square miles (15 to 50 km2). Ranges of adult males are usually several times larger.

Black bears are powerful animals that have few natural enemies. Despite their strength and dominant position, they are remarkably tolerant of humans. Interactions between people and black bears are usually benign. When surprised or protecting cubs, a black bear will threaten the intruder by laying back its ears, uttering a series of huffs, chopping its jaws, and stamping its feet. This may be followed by a charge, but in most instances it is only a bluff, as the bear will advance only a few yards (m) before stopping. There are very few cases where a black bear has charged and attacked a human. Usually people are unaware that bears are even in the vicinity. Most bears will avoid people, except bears that have learned to associate food with people. Food conditioning occurs most often at garbage dumps, campgrounds, and sites where people regularly feed bears. Habituated, food-conditioned bears pose the greatest threat to humans (Herrero 1985, Kolenosky and Strathearn 1987).

Range, Habitat, and Food Habits of Black Bear

Range

Black bears historically ranged throughout most of North America except for the desert southwest and the treeless barrens of northern Canada. They still occupy much of their original range with the exception of the Great Plains, the midwestern states, and parts of the eastern and southern coastal states (Fig. 3). Black bear and grizzly/brown bear distributions overlap in the Rocky Mountains, Western Canada, and Alaska.

Habitat

Black bears frequent heavily forested areas, including large swamps and mountainous regions. Mixed hardwood forests interspersed with streams and swamps are typical habitats. Highest growth rates are achieved in eastern deciduous forests where there is an abundance and variety of foods. Black bears depend on forests for their seasonal and yearly requirements of food, water, cover, and space.

Food Habits

Black bears are omnivorous, foraging on a wide variety of plants and animals. Their diet is typically determined by the seasonal availability of food. Typical foods include grasses, berries, nuts, tubers, wood fiber, insects, small mammals, eggs, carrion, and garbage. Food shortages occur occasionally in northern bear ranges when summer and fall mast crops (berries and nuts) fail. During such years, bears become bolder and travel more widely in their search for food. Human encounters with bears are more frequent during such years, as are complaints of crop damage and livestock losses.  Fig. 3. Range of the black bear in North America.

Identification of Black Bear

ID Black Bear

The black bear (Ursus americanus, Fig. 1) is the smallest and most widely distributed of the North American bears. Adults typically weigh 100 to 400 pounds (45 to 182 kg) and measure from 4 to 6 feet (120 to 180 cm) long. Some adult males attain weights of over 600 pounds (270 kg). They are massive and strongly built animals. Black bears east of the Mississippi are predominantly black, but in the Rocky Mountains and westward various shades of brown, cinnamon, and even blond are common. The head is moderately sized with a straight profile and tapering nose. The ears are relatively small, rounded, and erect. The tail is short (3 to 6 inches [8 to 15 cm]) and inconspicuous. Each foot has five curved claws about 1 inch (2.5 cm) long that are non-retractable. Bears walk with a shuffling gait, but can be quite agile and quick when necessary. For short distances, they can run up to 35 miles per hour (56 km/hr). They are quite adept at climbing trees and are good swimmers.

It is important to be able to distinguish between black bears and grizzly/ brown bears (Ursus arctos). The grizzly/brown bear is typically much larger than the black bear, ranging from 400 to 1,300 pounds (180 to 585 kg). Its guard hairs have whitish or silvery tips, giving it a frosted or “grizzly” appearance. Grizzly/brown bears have a pronounced hump over the shoulder; a shortened, often dished face; relatively small ears; and long claws (Fig. 2).

Grizzly Bear Biology and Behavior

Grizzly (brown) bears are typical of all bears physiologically, behaviorally, and ecologically. They are slow growing and long-lived (20 to 25 years). Their ability to store and use fat for energy makes long denning periods (5 to 7 months) possible. During denning they enter a form of hibernation in which their respiration rate (approximately 1 per minute) and heart rate (as low as 10 beats per minute) are greatly reduced. Their body temperature remains just a few degrees below normal; they do not eat, drink, defecate, or urinate, and their dormancy is continuous for 3 to 7 months. The adaptive value of winter denning relates to survival during inclement weather, when reduced food availability, decreased mobility, and increased energy demands for thermoregulation occur. Continue reading Grizzly Bear Biology and Behavior

Grizzly Bear Food Habits

Food gathering is a top priority in the life of grizzly bears. They feed extensively on both vegetation and animal matter. Their claws and front leg muscles are remarkably well adapted to digging for roots, tubers, and corms. They may also dig to capture ground squirrels, marmots, and pocket gophers. Brown bears are strongly attracted to succulent forbs, sedges, and grasses. In spring and early summer they may ingest up to 90 pounds of this high-protein forage per day. Bears gain their fat reserves to endure the 5- to 7-month denning period by feeding on high-energy mast (berries, pine nuts) or salmon. The 2 1/2- to 3-month summer feeding period is particularly crucial for reaching maximum body frame and preparing for the breeding season and winter. Continue reading Grizzly Bear Food Habits

Grizzly Bear Range

Grizzly Bear Range 

The brown bears of North America have lost considerable range, and are currently restricted to western Canada, Alaska, and the northwestern United States. Their populations are considered secure in Canada and Alaska, but have declined significantly in the lower 48 states. Before settlement, 100,000 brown bears may have ranged south of Canada onto the Great Plains along stream systems such as the Missouri River, and in isolated, small mountain ranges such as the Black Hills of South Dakota. They were scattered rather thinly in Mexico and in the southwestern United States, but may have numbered about 10,000 in California, occupying the broad, rich valleys as well as the mountains. Continue reading Grizzly Bear Range

Economics of Black Bear Damage and Control

Black bear damage to the honey industry is a significant concern. Damage to apiaries in the Peace River area of Alberta was estimated at $200,000 in 1976. Damage incidents in Yosemite National Park were estimated to be as high as $113,197 in 1975, with $96,594 resulting from damage to vehicles in which food was stored. Thirty percent of all trees over 6 inches (15 cm) tall were reported to be damaged by black bears on a 3,360 acre (1,630 ha) parcel in Washington State. In Wisconsin, one female black bear and her cubs caused an estimated $35,000 of damage to apple trees during a two-day period in 1987. In general, black bears can inflict significant economic damage in localized areas.Some states pay for damage caused by black bears. In western states, losses caused by black bears are usually less than 10% of total predation losses, although records are not complete. The extent of claims paid are not high but usually are greater than the license income that state wildlife agencies receive from black bear hunters. Deems and Pursley (1983) listed the states and provinces that pay for black bear depredations.