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A subspecies of the brown bear family, the grizzly bear is one of the worlds largest
land predators. Growing to an average of 6 to 7 feet in length and weighing between
400 and 600 pounds. Some larger male grizzlies can reach as much as 800 pounds or
more. Despite this size, adult grizzly bears can reach speeds of 40 mph. Coloring
of the grizzly bear can range from blonde, to deep hues of brown, or red. The most
distinguishing characteristic of the grizzly is a large hump, located above the
front shoulder. This powerful muscle mass is used to power the forelimbs while the
bear digs. Powerful hind legs allow the bear to stand completely erect at times,
giving a better view of the surroundings or reaching for food.
Currently grizzly bears in North America can only be found in about 1% of their
original home range. Most commonly found in western Canada and Alaska, grizzly bear
ranges include (in smaller numbers), Idaho, Montana, Washington, and Wyoming. Recent
sightings have been documented as far south as Colorado and possibly northern California.
Grizzly bear by the numbers
Today, the grizzly bear population hovers at around 60,000 in North America with
the greatest populations into Canada. An legally protected animal, the grizzly bear
is expected to repopulate much of its former range. This process will be slow however,
due to the human ramifications and the bear's slow reproductive habits. Grizzly
bears evoke a great deal of time into raising their young.
Unlike some bear species, grizzly bears lead a much more solitary life, except when
breeding, cub rearing, or near an abundant food supply. Preparing for winter, these
bears will gain tremendous amounts of body fat, before going into false hibernation.
Unlike other bear species, grizzlies may not hibernate at all if ample food supplies
are found throughout the winter months. Hibernating in dens typically at elevations
of 6,000 feet or more, grizzly bears are known to still move around on occasion
and even partially "recycle" their own body wastes.
Typically when grizzlies do hibernate it can be for periods of 5 to 8 months at
a time, depending on the winter. It is at this time female bears will give birth
to their young. These cubs, which are less than 1 pound at birth, must be nursed
by the mother while in the den. When spring arrives these cubs should weigh about
20 pounds.
Unlike other North American bear species, as grizzly bears emerge from their dens
in spring they will actively seek out prey such as young deer or elk calves. Where
human populations are present, sometimes livestock can be targeted.
Female grizzly bears reach breeding maturity at 3 or 5 years of age and can breed
about every 2 years. Male bears reach sexual maturity at about the same age, but
may not win breeding rights because of size. Similar to most mammals, bears often
fight for breeding rights to be accepted by females.
During the mid summer months of June and July, female grizzlies come into their
estrous cycle, usually lasting 3 weeks. During this time it is not uncommon for
a single female to be mated by more than one male. With a gestation period of around
220 days, typically female bears give birth to small liters of 1 to 3. The cubs
weigh in at less than 1 pound, often no bigger than a chipmunk. Although completely
helpless at birth, the cubs are strong enough to suckle on their mothers fatty milk.
The cubs will wean of their mothers from birth through September or October of their
first year, staying with their mothers until the following summer when they reach
about 1 1/2 in age. It is at this time the female will go into estrous again.
Grizzly bear cub survival is completely dependant on the mother. She must show them
how to forage, how to kill, where they must den, and where to hide in case of danger.
Like most young bears, grizzly bear mortality rates are often high.
Although grizzly bears can be extremely proficient predators, their diets consist
of mainly of berries, roots, nuts, flowers, grasses, and other vegetation. The claws
of all bears in general have adapted to digging up such food sources. At certain
times of the year, these Omnivores, prey on fish, small or young mammals, carrion,
and even black bears. Opportunistic hunters, grizzly bear aggression during periods
of hunger can lead them into conflict with other species, including wolves and humans.
Diets of grizzly bears are generally high in carbohydrates, consequently lower in
protein and fats. However these bears generally prefer foods containing higher proteins
and fats such as fish. Grizzly bears who do diet on higher protein foods along inter-coastal
regions are often much larger than their interior cousins. As grizzly bears emerge
in spring from their winter dens, they tend to continue to loose weight with food
scarcity. However, unlike black bears, grizzlies will quickly become predators and
hunt with much more aggression. With summer, and the many diverse food groups that
will flourish in bear ranges, recovery from the energy and fat loss from the previous
year is important to their survival. Grizzly bears will begin accumulating large
fat reserves again as fall approaches, primarily from fish, insects, fruits, and
roots.
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