 |
|
The American black bear prefers forests with occasional open areas. The species is found over a very large area of North America, from the northern tree limit of the Arctic to the Sierra Madre Mountains in northwestern Mexico.
The total population is estimated at somewhere between 400,000 and 750,000 in 32 American states, all of Canada’s provinces and territories except for Prince Edward Island, and five Mexican states.
Physical Characteristics
While black bears usually are black in the eastern part of North America, the fur color of the species varies greatly, and individual animals go through seasonal color phases. Colors actually range from blond through beige, cinnamon, blue-white, and dark brown to light black.
Size also varies greatly, depending on season, climate, and food availability. A black bear can gain up to 30 pounds per week in autumn. The adult male is generally from 35 to 40 inches tall on all fours, with a body length of 4 1/2 to 6 feet. Weight ranges from 125 to up to 600 pounds; the adult female is about three-quarters the size of the male.
The black bear has a heavy body, with a short tail and rounded ears. Its claws are short and curved, as an adaptation for tree climbing. Black bears are excellent climbers and they can move with surprising speed, more than 25 miles an hour over short distances.
Food and Diet
Although black bears belong to the order Carnivora (meat-eating), they are basically vegetarians. In the wild 75% of a black bear’s diet is plant food, which includes berries, fruit, grasses, and nuts. They also eat insects, small animals, carrion, and sometimes fish.
This vegetarian diet is supplemented by animal matter such as ants and other insects, fish and small marine mammals, and decaying carcasses. Black bears may also prey on small mammals such as ground squirrels and young elk.
Bears like to feed when it’s fairly cool, in the early morning or the evening. When it’s hot, they prefer to relax in the shade, either in the forest or in heavy underbrush.
Life Cycle
Female black bears usually become mature at 3 to 5 years of age. The mating season ranges from early May in warmer climates to early August in colder areas. It lasts two to three weeks, during which a female will typically mate with several males. Bears mark their territory by standing on their hind legs and clawing trees.
The fertilized ovum divides several times, then floats free in the uterus with no further development for about six months before attaching itself to the uterine wall. This process, known as delayed implantation, helps the mother build up her fat reserves as the hibernation period approaches.
Cubs are usually born in January or February, while the mother is hibernating. The number of cubs ranges from one to four, with two being most common.
Newborn cubs are hairless, blind, and tiny, weighing only about 8 to 12 ounces. They suckle on the mother while she’s still asleep and they develop very rapidly because the milk is so rich; it contains more than 20% fat, compared to about 4% fat in human milk.
When the mother leaves the den after hibernation, the cubs are ready to go with her. They stay with her for the first year of their lives. The mother usually drives them away during late spring or early summer of the second year, when she’s ready to mate again.
Young bears may spend some together after leaving the mother, but more often they separate. Black bears are solitary creatures who live and forage on their own, coming together only to mate or, occasionally, when there’s a rich food source that they can share.
Survival isn’t easy during the first couple of years. Bear cubs are threatened by many predators, including eagles, bobcats, wolves, mountain lions, and even adult male bears. However, if they survive those early years, the life expectancy of a black bear in the wild is 25 years or more.
Hibernation
When food is plentiful, during the late summer and early fall, bears gorge themselves to fatten up for the winter. A large male may gain as much as 30 pounds a week during this time of the year.
Most black bears hibernate for four to seven months. In warmer climates, though, bears may hibernate only briefly or not at all.
Hibernation allows bears (and many other animals) to survive through long periods without food. As cold weather arrives, the bear digs a den or finds one ready made, in the form of a cave, hollow log, tree cavity, or a heavy pile of brush. The den becomes a winter home.
During hibernation, a bear’s metabolism slows down and respiratory and heart rates drop from its normal 40-70 beats a minute to only 8-12 beats a minute. Unlike other hibernators, their body temperature drops only slightly (5 – 9 degrees Fahrenheit).
Basically, the bear lives on its accumulated fat while hibernating. The animal will lose anywhere between 15 to 30 percent of its body weight during this period.
Hibernation typically lasts until April or May, when the bear emerges from its den and begins foraging once again.
