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Learn more about polar bears and how
climate change is affecting them
Polar bears are amazing creatures. Ursus
maritimus, or “sea bear,” is the largest of
the bear family. Its wintry white coat makes the polar bear
stand out from all of its relatives. The polar bear is
massively built and breathtakingly beautiful, leaving a
lasting impression of power and grace in motion. Because
the polar bear fits in perfectly with the arctic landscape,
the bear has become a symbol for that northern polar region
– when we think of the arctic, we think of polar bears, and
vice-versa. And because the arctic is one of the first
areas to feel the brunt of climate change, the polar bear
has become the icon that we associate with our present
climate crisis.
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Let’s take a step back in time to the
Pleistocene epoch, the time period that includes the present
back to around 1 million years ago, when the descendents of
the polar bear first started to develop. Fossil evidence
shows that cave bears evolved into an early form of brown
bear that lived around 200,000 years ago. To live in the
frigid arctic temperatures, these bears eventually adapted
and evolved into an early version of the polar bear of
today. This early polar bear was even larger than today’s
bears – imagine that!
Today’s polar bear, though smaller than its
early relatives, is still the world’s largest land
carnivore. But they don’t start out large; in fact, the
mighty polar bear starts out life as a tiny cub, weighing
only 1 to 1˝ pounds. After mating in the spring, mother
polar bears spend the next several months storing large
amounts of fat that will sustain her during her long months
in the den.
Sometime in the fall, the moms will come
ashore and dig a den, then give birth in December or
January. The cubs – usually two of them – are blind and
helpless. The mother and cubs leave the den around March or
April, when the cubs weigh around 25 to 30 pounds. They
will stay with their mom until they are 1˝ to 2˝ years old,
learning how to hunt and survive. At maturity, the polar
bear is impressive in size. Weighing in at 330 to 1,500+
pounds, they stand at 6˝ to 11 feet tall, with females at
the lower end of the range.
 Polar bears are marvels of evolution. To be
able to live in the cold arctic environment, they developed
4˝ -inch thick layers of fat and huge padded feet. Their
broad paddle-like forepaws act like snowshoes for walking on
ice and snow, and work like oars when they swim. Their ears
and tails follow Allen’s Rule, which says that the further
north an animal is found, the smaller these extremities will
be. In addition, the bear’s large body means an efficiency
in conservation of energy.
The polar bear’s fur is clear. Light
reflects off of the hollow, straw-shaped hairs, making them
appear white. Sometimes the bear’s hair can appear yellow
because of staining, and sometimes polar bears in zoos in
warmer climates grow algae inside of their hairs, giving
them a greenish tint. Polar bear skin is black, which
scientists used to believe allowed the bears to soak up heat
from the sun. They now know this is not so. When the bears
need the warmth in the winter months, the arctic world is
dark. In the summer months, polar bears actually overheat,
and have been seen rolling in mud and using other methods to
get cool.
Polar bears rely heavily on their sense of
smell for finding food and other bears. With their keen
sense of smell, polar bears can detect prey from as far away
as 20 miles, even through snow or ice that is six feet
thick. As they walk through their environment, they are
constantly sniffing the air. A polar bear probably has
eyesight equal to a human’s.
Polar bears are solitary, living and hunting
on their own, with the exception of females raising cubs. And just like us, they prefer certain foods. Their prefer
marine mammals called ringed seals. They stalk and catch
the seal pups, although they will eat an adult if they can
catch one. But in the absence of these seals, polar bears
will eat just about anything. They have been observed
eating walruses, birds, bird eggs, small mammals, crabs,
starfish, grasses, mushrooms, algae, and even dead animals
like whales.
Polar bears are awesome swimmers! With their
huge paws they propel their bodies through seawater at 6˝
miles per hour. Their blubbery fat layers allow them to
stay buoyant, but when they submerge, they can stay under
water for two minutes. These marine mammals can also swim
long distances, up to 60 miles or even farther.
Recent population counts estimate that there
are only 20,000 to 25,000 polar bears left in the wild. They live in five countries in the northern hemisphere: in
Canada, from the northern arctic islands south to the Hudson
Bay, and in Greenland, Norway, Alaska in the U.S., and on
the northern coast of the former Soviet Union.
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Aquila at the Louisville Zoo in 2007. He is
currently living at the North Carolina Zoo. |
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Today polar bears face unparalleled
challenges. They depend on sea ice to live, which they hunt
on and use to move from one place to another. This ice is
melting at an alarming rate from increases in global
temperatures, forcing bears to swim further and longer and
causing many bears to drown. Birthing dens are collapsing,
causing further deaths, and hungry bears are hunting and
eating other polar bears. Up until recent climate changes,
polar bears could have up to four healthy cubs. Now,
because the mother bears are starving, they are lucky to
have one healthy cub. In addition, the polar bear’s prey is
dependent on the ice, so the loss of ice is threatening
their existence, which in turn affects the bears. Climate
change is and will have devastating consequences for the
entire arctic ecosystem.
I can’t imagine a world without polar bears,
but they probably will not be able to survive as a species
without the summer sea ice. They simply cannot adapt
quickly enough to keep up with climate change. Their only
hope is for man to do everything in his power to halt this
worldwide crisis before it is too late. These magnificent
creatures help identify one of the most incredible
ecosystems on our planet. They are bold, beautiful, and
awe-inspiring. Please help us save them from extinction by
becoming a steward for this world that we all call “home.”
Sources:
Polar bears International website,
www.polarbearsinternational.org
Polar Bears, by Ian Stirling. The
University of Michigan Press, 1998.
Impacts of a Warming Arctic; Arctic
Climate Impact Assessment, by Susan Joy Hassol. Cambridge University Press, 2004
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