January 1998
U.S. Fish & Wildlife Service
Polar Bear
Ursus maritimus
The polar bear, or “Nanuuq,” as
the Eskimos call it, lives only in the
Northern Hemisphere, on the arctic
ice cap, and spends most of its time in
coastal areas. Polar bears are widely
dispersed in Canada, extending from
the northern arctic islands south to
the Hudson Bay area. They are also
found in Greenland, on islands off the
coast of Norway, on the northern coast
of Russia, and on the northern and
northwestern coasts of Alaska in the
United States.
Some polar bears may make extensive
north-south migrations as the pack ice
recedes northward in the spring and
advances southward in the fall. They
also may travel long distances during
the breeding season to find mates or in
search of food.
Appearance
The polar bear is the largest member
of the bear family, with the exception
of Alaska’s Kodiak brown bears, which
equal polar bears in size. Males stand
from 8 to 11 feet tall and generally
weigh from 500 to 1,000 pounds, but
may weigh as much as 1,400 pounds.
Females usually stand 8 feet tall and
weigh 400 to 700 pounds. Part of the
reason the polar bear weighs so much
is that it stores about a 4-inch layer of
fat to keep it warm. The polar bear has
a longer, narrower head and nose, and
smaller ears, than other bears.
Although the polar bear’s coat appears
white, each individual hair is actually
a clear, hollow tube. Some of the sun’s
rays bounce off the fur, making the
polar bear’s coat appear white. During
the summer months, adult bears molt,
or gradually shed their coats and grow
new ones, which look pure white. By the
following spring, their coats will have
turned to a yellowish shade sometimes
due to staining from seal oils.
The polar bear’s coat helps it blend in
with its snow-covered environment, and
this is a useful hunting adaptation. The
polar bear’s front legs appear slightly
bow-legged and pigeon-toed, and fur
covers the bottoms of its paws. These
adaptations help the polar bear from
slipping on ice.
Feeding Habits
Because the polar bear rarely eats
vegetation, it is considered a carnivore,
or meat-eater. The ringed seal is the
polar bear’s primary prey. A polar bear
may stalk a seal by waiting quietly
for it to emerge from its blow hole or
“atluk,” an opening seals make in the ice
allowing them to breathe or climb out
of the water to rest. The polar bear will
often have to wait for hours for a seal to
emerge. Because the polar bear’s coat
is camouflaged against the whiteness of
the ice and snow, the seal may not see
the bear. Polar bears typically eat only
the seal’s skin and blubber, or fat, and
the remaining meat is an important food
source for other animals of the Arctic.
For example, some Arctic foxes feed
almost entirely on the remains of polar
bear kills during the winter.
Polar bears also prey on walrus, but,
because of the walrus’s ferocity and
size, bears are usually only successful
preying on the young. The carcasses
of whales, seals, and walrus are also
important food sources for polar bears.
In fact, because of their acute sense of
smell, polar bears can sense carcasses
from many miles away.
Polar bears can cover significant
distances on land, but are most agile in
the sea. They are excellent swimmers,
and can reach speeds of up to 6 mph in
the water. They are good divers, too.
When being pursued by hunters in open
water, polar bears have been known to
escape by plunging 10 to 15 feet below
the surface and resurfacing a good
distance away. They also have been seen
swimming 100 miles or more from ice or
land.
Reproduction
Polar bears reach breeding maturity at
3 to 5 years of age. Males may travel
great distances in search of female
mates. While breeding usually takes
place in April and May, the embryos
may not implant (develop) until the
following year, depending on whether
the mother has had a stable enough
supply of food to sustain herself while
allowing her to feed the developing cubs
through the winter.
Female polar bears prepare small dens on the mainland or on sea ice where they will
give birth and spend winter. Usually two cubs are born in December or January. While
the cubs are born blind, hairless, and no bigger than squirrels, they grow very rapidly.
Polar bear cubs remain with their mother for 2-1/4 years.
Steve Amstrup/USGS
Act in May of 2008. In addition, in
the United States, polar bears are a
federally protected species under the
Marine Mammal Protection Act of
1972. Regulations prohibit hunting
of polar bears by non-Natives and
establish special conditions for the
importation of polar bears or their parts
and products into the United States.
Eskimos and other Alaska Natives are
allowed to harvest some polar bears for
subsistence and handicraft purposes.
The Fish and Wildlife Service is the
federal agency responsible for managing
polar bears under the Endangered
Species Act and the Marine Mammal
Protection Act.
An international conservation
agreement for polar bears signed in
1976 by the United States, Russia,
Norway, Canada, and Denmark
(Greenland) also provides for
cooperative management of polar bears.
The Fish and Wildlife Service and the
U.S. Geological Survey’s Alaska Science
Center work together to monitor polar
bears in Alaska, where they number
approximately 3,500, and study their
behavior. Cooperative efforts with
Canada involve monitoring polar bears
in the Beaufort Sea, and the agencies
work with the Russian government to
monitor the animals in the Chukchi Sea.
Another treaty, the “Agreement between
the Government of the United States
of America and the Government of the
Russian Federation on the Conservation
and Management of the Alaska-
Chukotka Polar Bear Population,”
unifies the American and Russian
management programs that affect this
shared population of bears. Notably, the
In October and November, pregnant
females seek sites on the mainland or
on sea ice to dig small dens in snow
where they will give birth and spend the
winter. The temperature inside the polar
bear’s den can be as much as 40 degrees
warmer than outside. Usually two cubs
are born in December or January. When
the cubs first arrive, they are blind,
hairless, and no bigger than squirrels.
However, the cubs grow rapidly from
their mother’s rich milk.
As soon as spring comes, the mother
bear leads her cubs to the coast along
the open sea, where seals and walrus
are abundant. The mother will fiercely
protect her cubs from any perceived
danger. The cubs remain with their
mother for 2-1/4 years. Because of this,
most adult female polar bears breed
only every third year.
Special Adaptations
The blubber and fat of ringed seals
provides polar bears with the nutrients
they need to stay warm in their harsh
environment. They can eat other
sources of food, but their bodies demand
the high caloric intake available from
ringed seals. Terrestrial sources cannot
meet the high caloric needs of polar
bears, and consequently terrestrial
foods cannot substitute for the loss of
access to seals. Polar bears store energy
in the form of fat, most of which they
acquire from consuming these seals.
The most productive seal-hunting
periods are during the spring and early
summer (before the ice retreats) and
following the open-water period in the
fall. Because changes in sea ice are
most dramatic during the summer/fall,
this is the time when it can be hardest
for bears to hunt seals. A reduction
in sea ice can extend the time period
during which bears do not have access
to their primary prey. The effects of a
longer icefree season can cause a decline
in polar bear health, reproduction,
survival, and population size. Polar bear
survival depends on large and accessible
seal populations and vast areas of ice
from which to hunt.
Protection
Polar bears have traditionally played
an important role in the culture and
livelihood of Eskimos and other Native
people of the North, some of whom
depend on the animals for food and
clothing.
Because of ongoing and potential loss
of their sea-ice habitat resulting from
climate change, polar bears were listed
as a threatened species, across their
range, under the Endangered Species
U. S. Fish and Wildlife Service
Endangered Species Program
4401 N. Fairfax Drive, Room 420
Arlington, VA 22203
703-358-2171
http://www.fws.gov/endangered/
October 2009
treaty calls for the active involvement
of Native people and their organizations
in future management programs. It
also enhances long-term joint efforts
such as conservation of ecosystems and
important habitats, harvest allocations
based on sustainability, collection of
biological information, and increased
consultation and cooperation with state,
local, and private interests. The Fish
and Wildlife Service also undertakes
education and outreach efforts to inform
the public about how polar bears can be
protected from over-harvest.
A number of protective measures have
been taken to reduce human activities
along the coast in polar bear denning
areas, as the animals are most sensitive
to outside disturbances while denning.
For example, oil and gas pipelines and
roads have been routed to avoid these
areas. The Fish and Wildlife Service
also provides expertise to industries on
how to minimize conflicts with bears
while conducting their operations.
Today, it is estimated that there
are 20,000 to 25,000 polar bears
worldwide. With continued cooperative
management, it is hoped that these
great marine mammals, and the
unique arctic environment on which
they depend, can be protected for
generations to come.
Susanne Miller/USFWS
