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Black bears are usually black with a brown muzzle and often has a
white patch on the chest. Although black is the predominant color,
chocolate and cinnamon brown color phases are also common. Black
bears have a heavy body, short tail, rounded ears and a hind foot
with five toes. They are much quicker than their appearance would
suggest with recorded speeds being in excess of over 25 miles per
hour (40 kilometers per hour) for a short distance.
Adult male black bears range from about 50 to 75 inches (130 to 190
centimeters) in length and weigh 130 to 660 pounds (60 to 300 kilograms).
Females measure from 50 to 75 inches (130 to 190 centimeters) and weigh
90 to 175 pounds (40 to 80 kilogram). Black bears vary considerably in
size, depending on the quality of the food available. Males may be from
about 20 to 60 percent larger than females. At birth, cubs weigh 7 to 11
ounces(225 to 330 grams).
Black bears are omnivorous and feed on a wide range of foods, depending
on what is available. Insects (particularly ants), nuts, berries, acorns,
grasses, roots, and other vegetation form the bulk of their diet in most
areas. Black bears can also be efficient predators of deer fawns, elk and
moose calves. The black bear may also consume a variety of other small
mammals (ground squirrels, marmots, etc.) in their diet. In some areas of
coastal British Columbia and Alaska they also feed on spawning salmon.
Females reach sexual maturity at 3 to 5 years of age and males a year or
so later. Mating takes place in June, July, and August, and pairs may
remain together for only a few hours or for several days. Females will
normally mate with several males over the two to three weeks of the
breeding season. Females will normally breed every other year. Pregnancy
last about 220 days, and the cubs are born in a maternity den in January
and February. Litter size ranges from one to five, but two is the average.
Cubs may be weaned at six to eight months, but they remain with their
mothers for a year and a half. Consequently, the most often that female
black bears can mate, unless they lose their cubs prematurely, is every two
years. Longevity in the wild is 20 to 25 years.
At birth, the cubs are blind, hairless and very tiny. They weigh from 8½ to
11½ ounces (240 to 330 grams). Virtually helpless, they are, however, able
to move sufficiently to suckle on their mother who remains asleep. Her milk
is calorically very rich containing over 20% fat. In contrast, human milk
only contains about 4% fat.
Most black bears, including all who live in areas with severe weather
climates, will hibernate for between four and seven months. Where the
weather is much more temperate and the period without food available is
quite short, black bears may either not hibernate or they may simply nest
in a thicket or other sheltered area for brief periods of time.
While hibernating, a bear's heart rate drops from between 40 to 70 beats
per minute to only 8 to 12 beats per minute and its metabolism slows down
by half. Unlike many other animals who hibernate, its body temperature
only undergoes a minor reduction of 3 to 7 degrees Centigrade (5 to 9
degrees Fahrenheit). During the hibernation period, all bears lose a great
deal of weight. Adult males and adolescent bears lose between 15% and
30% of their weight while it is not uncommon for a female cub with
newborn cubs to have lost as much as 40% of her weight.
Most black bears vacate their winter dens in April or May. Both the
climatic conditions (snow cover and temperature) and physiological factors
such as the bear's age, the status of its health and its remaining fat
reserves affect the exact timing of emergence from its den. Normally,
adult males emerge first. Females with newborn cubs are usually the last to
leave their dens.
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