“Where I live”
Polar bears range across the circumpolar north, crossing the boundaries of five countries: Canada, Russia, the United States (Alaska), Denmark (Greenland) and Norway. More than 60% of all polar bears live primarily in Canada.
In spite of what is often portrayed in cartoons and advertisements, polar bears and penguins do not share a home range. Polar bears are found at the high latitudes of the Northern Hemisphere, while all penguin species are found in the Southern Hemisphere.
“How I live there”
Polar bears spend long, dark, frozen Arctic winters roaming across the sea ice in pursuit of prey. They are classified as marine mammals because they depend upon sea to provide food, feeding almost exclusively on seals. The scientific name for polar bears, Ursus maritimus, meaning “sea bear,” reflects this connection to the sea. But while polar bears are strong swimmers, they can hunt prey only from a platform of sea ice, and will swim between patches of sea ice only when necessary.
As a species, polar bears evolved in the intense cold, wind, and ice. They have two dense layers of fur and an additional layer of blubber up to 4.5 inches thick. The ears and tail are small, which helps minimize heat loss. A polar bear is so well insulated from the cold that even when temperatures drop to minus 34 degrees Fahrenheit, the bear’s body temperature and metabolic rate remain constant. Even in sub-zero temperatures, a polar bear can overheat if it runs too far or too fast.
Polar bear coats appear white but each strand of fur is actually clear and hollow. The hollow core of the strand scatters and reflects visible light in the same manner as ice and snow, which helps the bears blend into their Arctic environment. Beneath the fur, a polar bear’s skin is black.
Polar bears are also well adapted for moving and hunting on ice. Their huge webbed feet make excellent oars in the water and excellent snowshoes on land. The shape and large size of a polar bear’s feet help distribute its enormous weight so that the bear doesn’t fall through thinner ice. Its foot pads are covered in small black bumps called papillae that provide traction. The long, curved claws are lethal weapons and also help the bear to grip the ice when walking. A long neck allows the polar bear to reach down inside ice cracks and seal breathing holes to catch prey. Large, sharp canine teeth and small, jagged cheek teeth are perfect for ripping and tearing seal meat.
To catch a seal, a polar bear must be patient. Polar bears are generally solitary animals that hunt alone. Once a bear locates a seal breathing hole, it can sit there for hours – possibly even days – waiting for a seal to surface. When it does, the bear will strike, grabbing the seal with its jaws and yanking it from the water. Depending on what part of the range they inhabit, polar bears may try to catch and eat other prey as well, including sea birds and the occasional walrus or beluga whale. But without seals as their main diet, no polar bear can survive in the native range.
When spring comes to the Arctic and much of the sea ice thaws, polar bears retreat to land. There they remain until ice forms again in the fall. While land-locked, polar bears must fast. They will scavenge what they can – a whale or walrus carcass that washed ashore, kelp, or garbage – but they mostly go without food until they are able to return to sea and hunt seals again.
“Making my mark”
LIke any top predator in an ecosystem, polar bears significantly impact other species in that ecosystem. Polar bears and ringed seals are especially interdependent, with polar bears depending on ringed seals for sustenance and ringed seals adapting their behaviors to avoid polar bears. Arctic foxes and, to some extent ravens, benefit from scavenging remains of polar bear kills.
Where polar bears commonly encounter humans – for example, in and around Churchill, Manitoba, the “Polar Bear Capital of the World” – the large predators definitely make a lasting impression. Residents of Churchill have taken significant measures to coexist with polar bears and to build an ecotourism industry centered on viewing bears in their natural habitat without disturbing them.
“What eats me”
The polar bear is the dominant predator in its range and has no predators to fear other than humans and, on rare occasions, other polar bears. Indigenous and First Nations peoples have hunted polar bears for centuries.
Polar bears are typically solitary, unless a female has cubs. A female polar bear gives birth about once every three years, most commonly to twins. After giving birth, the female stays with her cubs for about two and a half years. Once those cubs are old enough to fend for themselves, the mother will separate from them and become pregnant again soon thereafter. She will live almost continuously with cubs until she is no longer reproductively viable.
Polar bears don’t hibernate like some other bear species. Only a pregnant female polar bear will den up for the winter. She will dig a maternity den in an icy snow bank and hunker down inside to give birth and care for her offspring for their first few months of life. When she emerges from the den, she will have been without food for many months, and her body’s fat stores are depleted. She will head out onto the sea ice as soon as possible to start hunting, with her cub or cubs following close behind.
Cubs are entirely dependent upon their mother. They will nurse for about 20 months and will learn to hunt and eat by her side. In fact, cubs learn everything about how to be a polar bear by watching their mother and following her lead. Mothers defend their cubs aggressively from any perceived threat. Mothers with cubs generally avoid adult male bears, which sometimes attack young, but will confront males if necessary. An agitated, highly protective polar bear mother is capable of driving off males much larger than herself.
Subsistence hunting of polar bears by Indigenous and First Nations peoples has generally not been severe enough to threaten the species as a whole, but the same cannot be said of sport and trophy hunting. In 1973, the five countries that are home to polar bears signed the International Agreement on the Conservation of Polar Bears. This agreement put important protections in place for polar bears, including strict regulation and limitation of sport hunting.
Yet even with those protections in place, the biggest threat to polar bears remains: a warming Arctic. Because of global climate changes, the long-term persistence of polar bears is in jeopardy, particularly in the lower Arctic. As temperatures warm and sea ice continues to melt earlier and form later, polar bears are unable to hunt adequately or build up the fat in their bodies. In May 2008, the U.S. Fish and Wildlife Service listed the polar bear as Threatened under the Endangered Species Act, making it the first animal species to win protections because of threats from global warming. This classification is consistent with that of IUCN, the world’s leading conservation organization, whose Polar Bear Specialist Group reclassified the polar bear as Vulnerable in 2005.
The Maryland Zoo works with other zoos and scientific organizations to carry out research that helps us understand more about and to protect this incredible species. And the Zoo has maintained a long-standing collaborative relationship with Polar Bears International (PBI), a not-for-profit organization dedicated to the worldwide conservation of polar bears through education and scientific research. In bringing people and polar bears together at the Maryland Zoo, we’re working to raise awareness of the causes of climate change and its extreme effects on the Arctic ecosystem, and to engage audiences in the community-level solutions necessary to ensure a future for polar bears.
- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Vertebrata
- Class: Mammalia
- Order: Carnivora
- Family: Ursidae
- Genera: Ursus
- Species: maritimus