Polar bears or “sea bears” are among the largest members of the bear family. They live at the top of the world in the Arctic Circle. Current populations are under threat because of over-hunting, poaching, pollution, global warming, and increasing oil and gas drilling.
Polar Bear
Habitat
- Polar bears live in the Arctic Circle, including the North Pole and northern parts of Europe, Asia, and North America.
- Arctic extremes include temperatures that range from -80 to 90 degrees Fahrenheit and light that ranges from almost total darkness in the winter to almost constant daylight in the summer. To deal with these extremes the polar bear must be fairly adaptable.
Distribution
- There are approximately 35,000 to 40,000 in the world.
- The largest populations live in Canada, Greenland, Siberia, and Alaska. Smaller populations also live in Norway.
Physical Characteristics
Color
- Polar bear fur varies in color from pure white to a yellowish hue.
- Their outer fur called ‘guard hair’ is actually clear and hollow (like a tiny glass tube), which allows polar bears to trap the sun’s heat and light. The guard-hairs are hard, smooth and shed water.
- They also have a dense layer of under-fur that traps a layer of air next to the skin.
- The fur layers actually keep the skin dry even when the bears swim in icy water.
- Their skin is black to absorb heat from the sun. Under their skin they also have a thick layer of fat to keep warm.
Size
- Polar bears are one of the largest land predators in the world.
- They can reach 4 feet tall (122 cm) or more at the shoulder.
- When they stand up on their hind legs they may be over 10 feet (305 cm) tall.
- Male polar bears weigh between 800 and 1600 pounds (360-720 kg), while females usually weigh between 400 and 800 pounds (180-360 kg).
- The largest recorded polar bear was a male that was over 12 feet (365 cm) tall and weighed over 2200 pounds (990 kg)!
Features
- Polar bears have a large body with a long neck and a proportionately smaller head than other bears.
- They have powerful, well-developed muscles in their hind legs and neck.
- Their massive forepaws are webbed for swimming.
- The soles of their feet are almost completely covered in dense fur to insulate them from cold.
- The parts of their feet that are not covered with fur are rough like sandpaper to prevent their slipping on ice.
- They have a short tail and small ears.
Diet
- Polar bears are excellent hunters and prefer ringed seals, although they eat a variety of food.
- The bears are adept at catching and killing the seals, which can weigh up to 150 pounds (67 kg).
- They often eat only the skin and the fat and leave the rest of the meat for scavengers.
- During the summer, the bears will eat seaweed (kelp) and range inland in search of alternative foods such as berries and grass.
- They do not eat fish. Most fish in the Arctic Ocean are very deep and polar bears are not deep sea divers.
- Usually polar bears kill a seal every five or six days.
- Polar bears can go for weeks without eating because they have huge stomachs and can eat up to 150 pounds (67 kg) of food at one sitting.
Behavior
Daily Activity
- Polar bears can range over 20,000 square miles.
- They generally stay close to shore, but have been sighted up to 100 miles inland.
- They spend a lot of time in water to catch food or escape danger.
- They are excellent swimmers and have been recorded more than 100 miles from the nearest shore in the water.
- They use their enormous webbed front paws as paddles and hind feet as rudders.
Hibernation
- Usually only pregnant females hibernate in winter. They use ice dens, similar to igloos, that they construct as temporary shelters.
- Most polar bears do not den, but enter a sort of ‘walking hibernation’ where they remain active, but rely on stored fat for energy.
- Sometimes they dig summer dens in the tundra or along coastal bluffs to escape summer heat and insects.
Reproduction
- Female polar bears start reproducing when they are between 3 and 5 years old.
- They usually mate in the late spring and give birth to two cubs in late December or early January.
- Like other North American species of bears, the embryo does not implant and begin to grow until the female enters the den in the late fall.
- When cubs are born they weigh only about two pounds each and are not much bigger than a rat. They are born without the ability to see or hear and have no hair.
- Fortunately, their mother keeps them warm and nourished until they are able to generate more of their own body heat.
- By April, the cubs usually weigh about 25 pounds (11 kg).
- They stay with their mothers for about three years to learn what they need about survival.
- The females are very protective of their young due to predatory males and other threats.
People and Polar Bears
Historically:
- For thousands of years, Inuit people have lived with polar bears and occasionally killed them for food or clothing.
- The Inuit never over-hunted the animals because it was too dangerous and hunting weapons were primitive.
- More recently, polar bears have been sought after by trophy hunters around the world and therefore have been over-hunted.
- By the late 1970’s scientists recognized that polar bear populations were too low and the bears were added to the endangered species list.
- Eventually the over-hunting was brought under control by the International Agreement on the Conservation of Polar Bears and Their Habitat in 1975.
- Polar bear numbers are growing.Currently:
- The biggest threat to polar bears is the impact of humans on their habitat.
- Even though the arctic is generally inhospitable to humans, oil and gas companies are very interested in this region.
- Oil and gas extraction can be very damaging to arctic ecosystems including the polar bears.
- There is still a lot to learn about the impacts of human expansion and encroachment, increasing tourism, and global warming on the polar bears.
