Polar bears are large, white bears that like cold climates, fatty meals and long days of hunting. No matter how adorable polar bears look, these animals are not cuddly. In fact, polar bears are ferocious hunters, and they are the biggest carnivores among land animals.
Size & appearance
Polar bears are also the largest species of bear. For bears, height is usually measured at the shoulder when the animal is on all fours, according to Polar Bear International. On average, polar bears on all fours are 3.5 to 5 feet (1 to 1.5 meters) tall, but when standing on its hind legs, an adult male polar bear may reach more than 10 feet (3 m). Lengthwise, they are 7.25 to 8 feet (2.2 to 2.5 m) from head to rump. Their tail adds another 3 to 5 inches (7.5 to 12.5 centimeters).
An adult male polar bear weighs around 775 to 1,200 lbs. (351 to 544 kilograms). The largest polar bear recorded weighed 2,209 pounds (1,000 kg), according to Polar Bear International. Females weigh half as much as their male counterparts, at only or 330 to 650 lbs. (50 to 295 kg).
Polar bears appear to be white, but their hair is actually transparent; the white results from light being refracted through the clear hair strands, according to the Animal Diversity Web (ADW), a database maintained by the Museum of Zoology at the University of Michigan. The bears can also be yellowish in the summer due to oxidation, or may even appear brown or gray, depending on the season and light conditions. Polar bear skin is black; it absorbs the heat of the sun to keep the animals warm.
Polar bears live in countries that ring the Arctic Circle: Canada, Russia, the United States (in Alaska), Greenland and Norway. In the winter, temperatures in the Arctic are usually around minus 29 degrees Fahrenheit (minus 34 degrees Celsius) and can reach as low as minus 92 F (minus 69 C). The temperature of the water is frigid, as well, reaching as low as 28 F (minus 2 C), the freezing point of seawater, according to PBS Nature.
Polar bears are excellent swimmers; their scientific name, Ursus maritimus, means "sea bear," according to the San Diego Zoo. They use their big front feet to paddle and their back legs as rudders. These bears have been known to swim more than 60 miles (100 km) without rest. [Images: Swimming Polar Bears]
Polar bears are solitary. The animal will spend its days sitting on the ice by a seal breathing hole, waiting for one to pop up. This style of hunting is called still-hunting. Polar bears will also seek out seal lairs, crash through the roof and kill the seals inside.
Unlike other bears, polar bears do not hibernate in the winter, according to the San Diego Zoo. They continue to hunt, unless the weather is extremely cold. Then they may seek shelter in a snow den.
The polar bear's primary food source is seals. Their diet of meat makes them carnivores. If the food supply is plentiful, they will only eat seal blubber. This high-calorie meal helps the bears build up fat reserves, which keep polar bears healthy between feedings and help maintain their body temperature. According to PBS Nature, polar bears need 4.4 lbs (2 kg) of fat each day. This is equal to about 121 lbs. of seal (55 kg) and provides about eight days' worth of energy.
If seal hunting isn't going well, polar bears will also eat anything they can find, such as fish, eggs, vegetation, reindeer, rodents, birds, berries and human garbage.
Females usually give birth during the months of November or December, after a gestation of eight months. In preparation, the animals dig a cave from a snow bank in which to have their cubs. This cave is called a maternity den.
A female polar bear typically gives birth to twins, though singles and triplets have been recorded. At birth, a cub weighs only 1.3 pounds (about half a kilogram), but they grow very quickly. Cubs depend on their mothers for warmth and fattening milk, which is 36 percent fat, according to the San Diego Zoo. By spring, the cubs are outside the den, exploring, and at two years of age they are fully mature. Polar bears live around 15 to 20 years.
According to the Integrated Taxonomic Information System (ITIS), polar bears are one of eight species in the Ursidae family. Their full classification is:
- Kingdom: Animalia
- Subkingdom: Bilateria
- Infrakingdom: Deuterostomia
- Phylum: Chordata
- Subphylum: Vertebrata
- Infraphylum: Gnathostomata
- Superclass: Tetrapoda
- Class: Mammalia
- Infraclass: Eutheria
- Order: Carnivora
- Suborder: Caniformia
- Family: Ursidae
- Genus & species: Ursus maritimus
According to the International Union for Conservation of Nature's (IUCN) Red List of Threatened Species, polar bears are vulnerable; their numbers are declining, and their habitat — sea ice — is shrinking. It is believed that there are only 20,000 to 25,000 polar bears living in the wild.The IUCN reports that the polar ice cap is predicted to completely melt within the next 100 years. This will leave polar bears without a home and will affect the polar bear population greatly.
Polar bears are listed on the U.S. Endangered Species List as threatened. They are protected under the Marine Mammal Protection Act, according to the U.S. Fish & Wildlife Service.
Their fat not only keeps polar bears warm, it also increases their buoyancy when they swim.
Polar bears have built-in socks. The bottoms of their paws are covered with fur to keep them warm and to help with traction in slippery situations.
A polar bear can sniff out a seal's breathing hole from more than half a mile away, according to the National Zoo. The bears can smell a seal on the ice 20 miles (32 kilometers) away.
Polar bears succeed in catching their prey in only 2 percent of their attempts, the National Zoo says.
The Inuit people still hunt polar bears for meat and fur, but hunting is carefully regulated by a quota system, according to Polar Bears International. Hunters pay respect to the bear's soul ("tatkok") by hanging the skin in an honored place in their igloo for several days. Inuit call polar bears "Nanuk" and believe they are wise, powerful and "almost a man."
The Sami (or Lapp) people refuse to say the polar bear's name for fear of offending it. Instead, they call it "God's dog" or "old man in the fur cloak," according to Polar Bears International.