JUST THE FACTS
Bears Family Tree
Polar bear / Grizzly bear
POLAR BEAR FACTS
SCIENTIFIC NAME: Ursus maritimus.
HABITAT: Most ice-covered seas of the Northern Hemisphere including Russia,
Norway, Greenland, the US and Canada. (See Cartographer’s table)
Distance polar bears can smell food from: 16 kilometers
Speed they can run: 56 kilometers per hour
POPULATION: The world population of polar bears is estimated to be 25,000
to 30,000 animals. The population in Canada is around 15,000
SIZE: The largest land carnivore in North America. They stand up to 1.6
meters tall at the shoulder and 2-3 meters from nose to tail.
WEIGHT: males—300 to 800 kilograms; females—150 to 500 kilograms
NUMBER OF YOUNG: litters average one to four cubs, usually two.
AGE AT MATURITY: males—10 to 11 years; females—5 to 6 years
LONGEVITY: 25-30 years in the wild
MARINE LIFE: Polar bears spend more time floating on ice than walking
on land. They are adept swimmers.
Speed they can swim: 10 km an hour.
Length of time they can swim without rest: 10 hours
Depth they can dive: 4.5 meters
Length of time polar bears can stay under water: up to 2 minutes
WHAT THEY EAT: Polar bears eat meat almost exclusively. Their main food
source is ringed seal. They have extremely large stomachs, which allow them to hold up to
70 kilograms of food. This enables them to survive for weeks without eating. During the summer
and early fall, when food is hard to find, bears have been known to scavenge the shoreline
for washed up carrion, bird eggs, rodents and berries.
HABITS: Polar bears do not hibernate, but pregnant females will make a
den and sleep. Although they are not hibernating, their body functions slow down at this
time. Many scientists call this “winter sleep,” because the bears can easily
be awakened. A mother polar bear can give birth and nurse her young while still in her winter
sleep. She will lose a great deal of weight—up to 40 percent of her body weight—by
the following spring.
REPRODUCTION: Mating season is from late March to mid July. Females will
mate with several males over that time. Once the egg is fertilized it detaches itself from
the womb, arresting its development. Over the summer the mother feeds, and if she builds
up enough fat, she digs herself a maternity den in October. This is when the development
of the baby resumes. The cub(s) are born sometime in December or January while the mother
is in her winter sleep. When the cubs are born they are blind, toothless, hairless and roughly
the size of a squirrel – about 25 centimeters long - weigh about 600 grams. They feed
on their mother's milk until she's ready to leave the den in early April. Cubs will stay
with their mother for about two years.
HUMAN ENCOUNTERS: Although polar bears hunt other animals, they rarely
kill people. In the last 25 years only six people have been killed by polar bears in Canada.
In all instances the animal was either starving or had been provoked.
Grizzly Bear Facts
SCIENTIFIC NAME: Ursus arctos. North America's grizzly bears are subspecies
of circumpolar brown bears, the same species as the European brown bear and the Asiatic brown
bear. Two recognized subspecies are found in North America: Ursus arctos middendorffi, the
Kodiak bears found on the Kodiak, Shuyak and Afognak islands of Alaska; and Ursus arctos
horribilis, which includes all the rest, regardless of their differences in size.
HABITAT: Grizzlies inhabit large forests with meadows, grasslands, plentiful
cover, varying elevation, and large river valleys.
POPULATION: the world population of brown bears is estimated to be 125,000
to 180,000 animals, about 100,000 of which live in the former Soviet Union. There are remnant
populations of 100 or fewer in Spain, France and Italy. Some 40,000 to 50,000 are found in
North America, roughly half in Canada. Only an estimated 1,200 remain within the lower 48
states.
SIZE: the second largest terrestrial North American carnivore (after the
polar bear), the grizzly varies considerably in size from one population to another. It can
reach 2.6 meters in length.
WEIGHT: adult males weigh 250 to 350 kilograms; adult females weigh 95
to 275 kilograms. The largest bears live on the west coast of British Columbia and Alaska,
where adult males may weigh more than 300 kilograms and adult females more than 200 kilograms.
NUMBER OF YOUNG: litters average one to four cubs, usually two. Females
breed at three-to-four-year intervals.
AGE AT MATURITY: males 8 to 10 years; females 4.5 to 7 years.
LONGEVITY: 15 to 25 years in the wild, occasionally more.
KNOWN DISTRIBUTION IN NORTH AMERICA: British Columbia, western Alberta,
Yukon, Northwest Territories, Alaska and, in reduced numbers, Wyoming, Montana, Idaho and
Washington.
WHAT THEY EAT: land animals, berries, fish, leaves, grasses, and roots.
Kilograms of food a grizzly may eat per day during the summer and fall: 35 to 40.
HABITS: During the winter, grizzly bears live in dens. Some grizzlies den
in caves or other natural shelters. Others build beds under branches or dig holes in the
ground. In the den, the female normally gives birth to one or two cubs. The cubs stay with
the mother 1.5 to 3.5 years, learning feeding and survival methods. Grizzlies fiercely protect
themselves, their young, and their food.
REPRODUCTION: Mating season is from spring until early summer. Females
will mate with several males over that time. Once the egg is fertilized it detaches itself
from the womb, arresting its development. Over the summer the mother feeds, and if she builds
up enough fat to last the winter, cubs will be born in January or February while the female
is still in her den. Most litters contain two cubs, but one, three, or even four is possible.
When cubs are born they weigh between 350 – 700 grams. They are blind and hairless.
The cubs feed off their mother’s milk and grow rapidly. The cubs remain with their
mother until June of their 3rd year.
HUMAN ENCOUNTERS: Most grizzly bears try to avoid contacts with people.
But grizzlies sometimes damage cabins and campsites or prey on livestock. On rare occasions,
they may attack people, and some people have been killed by grizzlies.
Lisa Pridmore
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