The Polar Bear
The polar bear is perfectly suited to live in the cold, harsh tundra of Alaska, Canada, Greenland, Norway, and Russia. Standing up to 10 feet tall, it is the world’s largest bear and the Arctic’s top predator. Its scientific name, Ursus maritimus, means “sea bear” for good reason. The polar bear spends much of its life in, around, or on the Arctic Ocean. A skilled swimmer, the polar bear can swim at a top speed of 40 kilometers per hour, paddling with its front paws while holding its hind legs flat like a rudder. Its paws are slightly webbed.
On land, its dinner plate-sized paws act like natural snowshoes when it walks on snow and ice. The polar bear is built to stay warm. The water-repellent outer layer of its fur is hollow and reflects light, giving it a white colour, which helps camouflage it in the snow. The skin underneath its fur is actually black. (You can see this yourself from its black nose.) There is a 4-inch layer of fat below the surface of the bear’s skin to trap body heat in the freezing Arctic environment. No cuddly teddy bear, the polar bear has quite the bite thanks to its 42 razorsharp teeth, jagged back teeth, and canines, which are larger than a grizzly’s. Other adaptations are a third eyelid to help protect the bear’s eyes from the elements, a blue tongue, and an excellent sniffer. The polar bear’s sensitive nose can smell a seal on ice 20 miles away.
This carnivore gives its seal of approval mainly to ringed and bearded seals. These seals provide them with large amounts of fat, which polar bears need to survive. The crafty bears rest silently at a seal’s breathing hole in the ice, waiting for the seal to surface, or pounce through the roof of the den to capture young seals. Polar bears also hunt by swimming beneath the ice. They spend more than 50% of their time hunting, catching maybe one or two seals for every 10 they hunt. Although they don’t hibernate, polar bears take a “winter sleep.” Their body functions do slow down, but they can easily wake up. While food is scarce for other types of bears in the winter, polar bears have seals to eat all winter long, so they don’t need to hibernate.
When it comes to dens, males and females are polar opposites. Males don’t live in dens, but pregnant females do. In the fall, females make dens in earth and snowbanks along the coast. They need the “heated” space to protect their tiny cubs. Dens can be 38°F warmer than the outside temperature. Litters of one to three cubs are born and fed during the winter sleep. At birth, babies are only 1.5 pounds—about the size of a stick of butter. They are born hairless with their eyes closed. Mother’s milk contains 35% fat to help the cubs grow quickly. By the time mother bear emerges from her den in spring, her cubs weigh more than 20 pounds. The tumbling “cub scouts” follow her out into the bright world, ready to explore and learn to hunt.
It’s lonely at the top—of the food chain. Polar bears eat everything, and nothing eats them, (except for native hunters). So why has their Hudson Bay population declinced by 20% in the past 20 years? Climate change, melting sea ice, and a decline in the number of seals are taking their toll. In 2011, a female swam for nine days nonstop to get to sea ice, losing her cub along the way. The United States Geological Survey (USGS) predicts that two-thirds of all polar bears will disappear by 2050.
