Marine Life Encyclopedia
Marine Mammals
Polar Bear
Ursus Maritimus
Distribution
Polar latitudes of the northern hemisphere
ECOSYSTEM/HABITAT
Ice edge
FEEDING HABITS
Aggressive predator
TAXONOMY
Order Carnivora (carnivorans), Family Ursidae (bears)
Polar bears are aggressive predators, known for taking a variety of prey. They spend most of the year associated with Arctic sea ice, where they hunt ringed seal and bearded seal pups. Polar bears have an excellent sense of smell and can locate pups even when they are buried in snow dens. Polar bears can easily use their size and strength to break open dens and feed on the helpless pups. Adult males have also been known to eat large aquatic animals, like beluga whales, that they attack from the ice and pull onto the ice surface. When on land (as opposed to surface ice), polar bears scavenge for dead animal matter. This species has no natural predator. It is one of the few species that is even considered to be higher on the food web than humans.
Courtship and mating take place on the ice surface, but birth generally takes place on land. Females give birth to (typically) two cubs, which weigh no more than a few pounds (~one kilogram). Cubs nurse for at least two and a half years, and as in all bears, the mother polar bear is aggressively protective of her offspring. Polar bears reach sexual maturity between ages four and six.
Polar bear populations are decreasing throughout their geographic range, and some populations have been depleted significantly. Scientists now believe the species to be vulnerable to extinction. While hunting for this species does occur, climate change is the primary threat to the polar bear’s existence. This bear is intimately tied to Arctic sea ice and to seals that require ice for reproduction, and that ice is expected to continue thinning and melting faster each summer in the face of climate change. Scientists are not sure if polar bears will be able to adapt to these rapidly changing conditions.
Fun Facts About Polar Bears
1. Polar bears are the largest bear species in the world,1 growing to a maximum length of 8.5 feet (260 cm) and weight of 1,543 pounds (700 kg), with males growing about twice as large as females.
2. Polar bears give birth to one to three cubs at a time, but most often birth twins that weigh only 1.3 pounds (0.6 kg).
3. Polar bears have black skin that’s covered in two layers of fur. The hollow, outer fur layer is nearly 6 inches (15 cm) long and reflects light, which is why it looks white.2
4. Pregnant polar bears build dens where they give birth and care for their young cubs for the first few months of their lives. The mother does not feed during this time and can go up to 8 months without food – the longest deprivation time of any mammal.
5. Polar bears are the most carnivorous species of bear, feeding primarily on ringed and bearded seals.3
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Additional Resources:
1 U.S. Fish & Wildlife Service
2 United Nations Food and Agriculture Organization
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