Polar Bears: Life in the Arctic

While winter takes its time arriving in Israel, far to the north in the Arctic lives the world’s largest land predator: the polar bear.

Its hollow hairs are translucent, but from a distance the coat looks white or cream. That appearance has earned it the name ‘white bear’ in many languages. Thick body fat and specialized fur protect it from the bitter Arctic cold, while its compact build helps retain heat.

The polar bear is a marine mammal that depends on sea ice and marine prey. Its powerful limbs help it travel over ice and swim between ice floes. An apex predator at the top of the food chain, it feeds mainly on seals but will take other food when the opportunity arises.

Polar bears are enormous. Adult males typically weigh 350 to 600 kg, while adult females usually weigh 150 to 290 kg. Newborn cubs are tiny by comparison.

Polar bear cubs. Photo: U.S. Fish and Wildlife Service, public domain.

Although closely related to brown bears, polar bears have evolved to fill a specialized ecological niche. Their bodies are adapted to freezing temperatures, travel across snow and ice, swimming, and hunting seals, their main prey.

Polar bears spend much of their lives on sea ice. Their scientific name, Ursus maritimus, means ‘sea bear.’ They hunt from floating sea ice and can live on stored body fat while waiting for their next meal.

A polar bear has a muscular body, a long neck, and small ears and a short tail that help limit heat loss. Its broad paws carry it over land and propel it through the water. They also spread its weight across deep snow. On thin ice, a bear may even move on its knees and elbows to distribute its weight and avoid breaking through.

The coat looks white from a distance, but its hairs are translucent. Hollow hairs provide insulation, while the skin beneath is black. The pale coat helps the bear blend into snow and ice. A water-repellent layer of oil adds protection from the cold, and stiff hair on the paws provides insulation and grip.

Male polar bears tend to live alone. They can be aggressive toward other males and may attack people. Females are more tolerant of one another. Males usually meet females during the breeding season, when competition with other males can lead to fights, injuries, and broken teeth.

Rest takes up much of a polar bear’s life. In the frozen Arctic, sleeping and resting conserve precious energy. Alongside 7 – 8 hours of regular sleep, bears nap whenever they can. Most remain active through winter, but pregnant females spend the winter in maternity dens, where they give birth and nurse their cubs.

Polar bears can travel long distances over land and ice, but prefer to stay near the sea. Their size makes chasing prey costly in energy, so they favor ambushes, using their camouflage and strong swimming skills.

Seals are their main prey, but polar bears also eat birds, rodents, shellfish, crustaceans, deer, sheep, and even fish. A bear may wait patiently beside a breathing hole in the ice, ready to catch a seal as it surfaces for air. After a successful hunt, it eats the skin and fat and leaves the meat for other animals. Those leftovers help other Arctic species survive in a harsh climate.

Polar bears mate in spring and early summer. Implantation is delayed until fall and depends on the female having enough fat to support herself and her cubs through the denning period.

Polar bears are classified as Vulnerable on the IUCN Red List. Trends vary among subpopulations; some are declining, while others are stable, increasing, or lack enough data. Global warming is reducing Arctic sea ice, steadily eroding the bears’ habitat and hunting grounds.