Polar bears: The largest land carnivores

The polar bear (Ursus maritimus) is the largest bear species and the top land-based predator on Earth. These immense bears roam the Arctic regions, hunting for their main prey, seals, across the icy terrain.

Polar bears are believed to have evolved within the last half-million years when a group of brown bears migrated north during a warmer period and became isolated. As the climate cooled again, these bears had to adapt to survive in the extreme Arctic conditions, according to Denmark’s Aarhus University Arctic Research Centre.

Adaptations to the Arctic

Polar bears possess several adaptations for life in the icy north. They have dense fur and a thick layer of fat to retain body heat, and their paw pads feature small bumps that provide traction on slippery ice, according to Polar Bears International. They are exceptional swimmers, earning their scientific name Ursus maritimus, which means “sea bear,” due to their strong reliance on marine environments. In fact, polar bears are the only bear species considered marine mammals.

Size and Weight

On all fours, polar bears typically stand 3.5 to 5 feet (1 to 1.5 meters) tall at the shoulder, while adult males can exceed 10 feet (3 meters) when standing upright, per Polar Bears International. One record from 1960 in Alaska reported a polar bear standing 12 feet (3.7 meters) tall, according to the National Wildlife Federation.

Adult males generally weigh between 770 and 1,300 pounds (350–600 kg), while females weigh roughly half that, between 330 and 650 pounds (150–295 kg). The enormous 1960 Alaskan male weighed 2,210 pounds (1,000 kg), the heaviest recorded bear.

Fur and Appearance

Polar bear fur is actually transparent; it appears white due to light scattering and reflection off hollow hair strands, helping them blend into their snowy surroundings. Their coats can also look yellowish, brown, or gray depending on the season and lighting. Underneath, their skin is black, absorbing sunlight to retain warmth.

Comparison with Kodiak Bears

Kodiak bears, a brown bear subspecies in Alaska, can rival polar bears in size. Isolated on the Kodiak Archipelago for around 12,000 years, these bears can grow over 10 feet tall on their hind legs and weigh up to 1,500 pounds (680 kg). Although polar bears are generally taller and heavier on average, individual Kodiak bears may surpass average polar bear size.

Range and Habitat

Polar bears inhabit the Arctic ice and surrounding regions, including Canada, Alaska, Greenland, Norway, Russia, and occasionally Iceland, according to the IUCN. They do not live in Antarctica, where penguins reside.

Diet and Hunting

As the most carnivorous bear species, polar bears rely almost entirely on meat. Their preferred prey is the ringed seal (Pusa hispida). They hunt by waiting at seal breathing holes or breaking into seal dens to capture their targets. When seal availability is high, polar bears focus on the blubber, which is calorie-dense and vital for building fat reserves, consuming up to 4.4 pounds (2 kg) daily.

Polar bears will also eat walruses, seabirds, fish, small mammals, whale carcasses, and minor vegetation when seals are scarce. Being apex predators, they have no natural predators other than humans.

Behavior and Reproduction

Polar bears are mostly solitary except for mothers with cubs, though unrelated individuals may gather around abundant food sources. They are not territorial but may fight over carcasses or mates. Mating occurs from March to June, with males locating females via scent trails.

After mating, fertilized eggs remain dormant until implantation occurs around September or November, with a total gestation period of about seven months. Pregnant females dig maternity dens in snowbanks to give birth, typically to twins in December or January. Newborn cubs weigh about 1.3 pounds (0.6 kg). Cubs nurse and grow rapidly, exploring outside the den after roughly 12 days and staying with their mother for up to three years to learn survival skills. In the wild, polar bears live 15–18 years on average but can reach their 30s. In captivity, one bear named Debby lived to 42.

Interaction with Humans

Polar bears rarely attack humans, but incidents do occur, often involving nutritionally stressed males. A study of attacks from 1870–2014 recorded 73 confirmed cases, including 20 fatalities. As Arctic ice diminishes due to climate change, bears spend more time on land, increasing potential human interactions.

Conservation Status

Polar bears are classified as vulnerable by the IUCN. Climate change, shrinking sea ice, and human activities like Arctic oil and gas development threaten their survival. The global population is estimated at around 26,000 individuals. In the U.S., polar bears are listed as threatened under the Endangered Species Act and are protected under the Marine Mammal Protection Act.

Indigenous peoples, including the Inuit, continue traditional hunting for sustenance and cultural practices, regulated to ensure sustainability. The Inuit call polar bears Nanuq and regard them as intelligent, powerful, and almost human-like, according to Polar Bears International.