10 Things You Didn't Know About Polar Bears

Polar bears are some of the most extraordinary and recognizable animals in the world. Scientifically known as Ursus maritimus, they are scarcely seen in the wild as they reside north of the Arctic Circle. They belong to the family Ursidae, containing the largest of all terrestrial carnivores, also including black and brown bears. These colossal creatures are powerful predators, equipped for frigid temperatures with their dense fur and thick layer of warming body fat. But they face an unstable future as their icy habitat is dwindling rapidly. Learn more about their conservation status and what makes them so fascinating.

1. Polar Bears Are Actually Black, Not White

Although polar bears are famous for their snow-white color, their skin is actually black, according to the World Wildlife Fund. What makes them look white is actually their thick layer of hollow, translucent, light-reflecting fur, effectively camouflaging them against snowy backgrounds. The only place where their true pigment is evident is on the tips of their charcoal noses. Their black skin helps them absorb sun rays, keeping them warm in bitter temperatures.

2. They Keep Warm With a Layer of Fat Inches Thick

Polar bears spend their lives in sub-zero temperatures, but they're built for it — not just with insulating fur and heat-absorbing skin but also with a layer of body fat that can be almost four and a half inches (11.4 centimeters) thick. That fat is what keeps them warm when they're in the water, and it's also why mothers are reluctant to let their cubs swim in the spring: Babies don't yet have enough body fat to keep them warm.

3. They Are Classified as Marine Mammals

Because they depend on the ocean to provide food and an icy habitat, polar bears are the only bear species to be considered marine mammals. This means they're grouped with seals, sea lions, walruses, whales, and dolphins, and they also fall under the Marine Mammal Protection Act. The act, which was signed into law in 1972, prohibits "taking" or importing any marine mammal in the U.S. (to "take" means to harass, hunt, capture, or kill in this context).

4. They Are Talented Swimmers

That being said, polar bears are quite graceful in the water. According to the WWF, they can swim at a sustained pace of six mph and can do so for long distances. They use their slightly webbed front paws to paddle, while holding their hind legs out flat like rudders.

Sometimes polar bears are spotted swimming hundreds of miles from land. They likely don't get that far out by paddling; rather, they sometimes hitch rides on floating sheets of ice. Even though they are strong swimmers, polar bears can get into trouble when storms kick up during their long outings. They can sometimes drown when they're far from land in turbulent waters. Research suggests that long-distance swimming may also have physiological and reproductive consequences.

5. They Really Love Seals

Polar bears spend about half their time hunting, and seals are their primary food source. Specifically, they look for ringed and bearded seals because they're high in fat, and fat is critical to a polar bear's survival. They hunt by looking for areas of cracked ice and waiting for seals to surface for air. They use their strong sense of smell to locate them and will often wait for hours or days. According to the WWF, fewer than two percent of their hunts are actually successful.

That's why they also scavenge whale carcasses and look for other food sources like bird eggs and walruses, says the National Wildlife Federation. They are at the top of the food chain in the Arctic and have no predators other than humans and other polar bears.

6. Polar Bears Can Be Loners

They spend much of their lives alone except in a few rare situations, like when several are feeding on a whale carcass at once. Females will stay with their cubs when they are raising them, and couples will stick together when they are mating. While their elders tend to be loners, young polar bears will often frolic and play with each other.

7. Their Origins Are Murky

For years, researchers believed that polar bears evolved from brown bears over the last 150,000 years or so, speculating that climate change forced them to evolve rapidly to adapt to living in the Arctic. But findings from another study published in the journal Science suggest that polar bears didn't descend from brown bears. After studying DNA from polar bears, brown bears, and black bears, researchers believe that the brown bear and polar bear have a common ancestor, but the lines split some 600,000 years ago.

8. Polar Bears Are Huge

Polar bears are about seven to eight feet long and four to five feet tall at the shoulder when on all four legs. A large male bear can weigh more than 1,700 pounds and can be as tall as 10 feet while standing on his hind legs. A large female can weigh up to 1,000 pounds.

Being so weighty, polar bears must walk carefully on the ice. To distribute their weight, they splay their legs out far apart, lower their bodies, and move slowly, according to Polar Bears International. Polar bears live an average of 25 to 30 years in the wild.

9. They Have Many Names

Science may know the polar bear as Ursus maritimus, but around the world, the species has plenty of interesting monikers, such as Thalarctos, "sea bear," "ice bear," Nanuq (to the Inuit), isbjorn (to Swedes), "white bear," and "lord of the Arctic." Norse poets called the bear a "white sea deer," "the seal's dread," the "rider of icebergs," "the whale's bane," and "the sailor of the floe." They said the bear had the strength of a dozen men and the wit of 11. The Sami or Lapp indigenous people from northern Europe called the bears "God's dogs" or "old men in fur coats." They refused to call them polar bears for fear of offending them.

10. They Are in Danger of Going Extinct

In 2008, polar bears were the first vertebrate species to be listed under the U.S. Endangered Species Act as threatened due to predicted climate change. Internationally, they are listed as a vulnerable species by the International Union for Conservation of Nature. Canada classifies polar bears as a species of special concern under the National Species at Risk Act.

The IUCN estimates that there are between 22,000 and 31,000 polar bears left worldwide. Their numbers are shrinking due to habitat loss and melting sea ice. When ice is lost, they have to travel longer distances to find stable ground, which can be a serious threat to their survival. Less ice also means fewer seals to eat.