The polar bear (Ursus maritimus) is the world’s largest land carnivore. It also shares the title of world’s largest bear with the omnivorous Kodiak brown bear. The polar bear is native to areas around the Arctic Circle and Arctic Ocean and over the years has developed many specialized body characteristics for dealing with the frozen marine environment in which it lives. Its Latin name means “sea bear”, as the polar bear spends much of its time in the water or hunting on seasonal sea ice.
Most male polar bears are 8-10 feet in length and weigh 770-1500lbs, with females being about half that size, except for when pregnant. The largest polar bear on record weighed an astonishing 2,210lbs. Much of this weight comes from the nearly 4 inches of insulating blubber that surrounds the bear and the translucent double-layer coat that covers its sunlight-absorbent black skin. Polar bears also have small dermal bumps on the pads of their feet and deeply grooved claws to enhance traction on the ice they spend so much of their lives on. Wide paws also help make them excellent swimmers.
The polar bear is almost purely a carnivore, and the majority of its diet comes from hunting ringed and bearded seals. The polar bear will usually hunt by waiting on sea ice near a seal breathing hole for a seal to surface, then swiping it out of the water and onto the ice. Other food sources include walrus, beluga whales and carrion. Female polar bears will also forage for vegetation. Unlike many carnivores, adult polar bears only eat the skin and blubber of animals they kill, which is rich in fat and calories. However juveniles are meat eaters, as they need the protein to grow. Polar bears also eat many other terrestrial creatures, but their specific biology requires that the majority of their calories come from sea life. Polar bears are also known to eat virtually any human garbage they come across including inedible items such as motor oil and car batteries, which can lead to sickness or death for the bears.
Polar bears are not territorial animals and will usually only show aggression towards humans or other animals if they are hungry. They are primarily solitary but do occasionally play and sleep together; this is particularly seen in young males.
Mating season takes place on sea ice between April and May, after which the female will spend the next several months trying to gain over 400lbs before winter. Once winter arrives in August or September the sea ice will be too frozen to allow for seal hunting and the female will head inland to dig a maternity den. These dens are usually dug in the snow and may include several rooms. After entering the den the female will enter a dormant state similar to hibernation, never actually falling asleep continuously. Between November and February she will give birth to a litter of two cubs who will survive off of her milk until the family emerges from the den in between mid-February and April. Once the cubs have learned to play and walk the family will finally trek back out to sea to hunt seals. Depending on how long it’s been since the ice floes froze the previous winter, the female may not have eaten for eight months at this point.
Female polar bears do not wean their cubs until 2 ½ years of age. During these first few years of dependency she will vigorously protect her cubs from being eaten by wolves, and even male polar bears. After weaning, the juvenile bears will be unceremoniously chased away from the den by their mother and will be forced to hunt and provide for themselves. Most polar bears live to be around 25 years old, with some in captivity living to beyond 40.
POLAR BEAR FACTS
- In 2008 it was estimated that the worldwide polar bear population was 20,000-25,000.
Polar Bears International