Description
The Polar bear (Ursus maritimus) is a hypercarnivorous bear found within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the largest extant bear species, as well as the largest extant land carnivore. Although it is the sister species of the Brown bear, it has evolved to occupy a narrower ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting seals, which make up most of its diet. Although most Polar bears are born on land, they spend most of their time on the sea ice.
Their scientific name means “maritime bear” and derives from this fact. Because of their dependence on sea ice, Polar bears are classified as marine mammals. For thousands of years, the Polar bear has been a key figure in the material, spiritual, and cultural life of circumpolar peoples, and these bears remain important in their cultures. Historically, the Polar bear has also been known as the “white bear”. It is sometimes referred to as the “nanook”, based on the Inuit term nanuq.
Appearance
Polar bears are large, stocky mammals well adapted to life on ice. Their bodies resemble those of brown bears but lack the shoulder hump, and they have smaller heads with elongated necks. Adult males typically weigh between 300 to 800 kg (660 to 1,760 lbs) and can reach up to 2.5 meters in length. Females are smaller, weighing 150 to 300 kg (330 to 660 lbs) and measuring 1.8 to 2 meters in length. At the shoulder, a polar bear stands about 1.6 meters tall.
Their thick fur consists of a dense undercoat and a layer of transparent guard hairs that appear white or yellowish due to light refraction. The fur may look yellowed with age or vary in tone based on season and lighting. Beneath the fur, polar bear skin is black, helping absorb heat from the sun. Their broad forepaws act as effective paddles when swimming, while the soles of all feet are covered in fur for warmth and traction. Paw pads feature small, soft dermal bumps (papillae) for grip on icy surfaces. The claws are deeply scooped underneath to help dig into ice. Polar bears move with a plantigrade gait, and females have four functional mammae.
Distribution
Polar bears have a circumpolar distribution across the Arctic region and are found throughout areas surrounding the North Pole. Their range spans parts of five nations: the United States (Alaska), Canada, Russia, Norway (Svalbard), and Denmark (Greenland). While they are rarely seen north of 88° latitude, polar bears range as far south as James Bay in Canada, the southern tips of Greenland and Iceland, and Newfoundland.
They primarily inhabit the annual sea ice over the continental shelf and the Arctic inter-island archipelagos—regions often called the “Arctic ring of life” due to their high biological productivity. Polar bears prefer areas where sea ice meets open water, such as polynyas and leads, which are ideal for hunting seals, their primary prey.
Seasonal movements follow the shifting ice. In winter, polar bears roam along the southern edge of the ice pack or coastal landfast ice. Pregnant females den on coastlines where suitable habitat is available. In summer, bears stay near the receding ice edge, on islands, or along coasts with lingering ice. Some may drift on ice floes or become temporarily stranded on land as sea ice retreats.
Six major population regions are recognized: Wrangel Island and western Alaska, northern Alaska, the Canadian Arctic Archipelago, Greenland, Svalbard-Franz Josef Land, and central Siberia.
Behavior
Polar bears are solitary animals, typically only coming together for mating or when a mother is raising her cubs. They may also interact when scavenging from a seal kill, though these encounters often end with the smaller or younger bear retreating. Females with cubs will aggressively defend their young from larger males.
Most of a polar bear’s time is spent resting—up to two-thirds of the day is used for sleeping, lying down, or waiting in a still-hunting position. The rest of the time is dedicated to traveling, either walking across the ice or swimming between ice floes, stalking prey, or feeding. They are excellent swimmers and may travel long distances in search of food, with some sightings reported as far south as Maine in the United States.
Polar bears are generally quiet but communicate through a variety of vocalizations and body signals. Mothers use moans and chuffs to communicate with cubs, while cubs may bleat when distressed or hum while nursing. Bears may huff, chuff, or snort when nervous, and growl or roar when threatened. They also rely on scent marking—leaving chemical signals in their tracks—to track one another across the Arctic.
Their sense of smell is highly developed, allowing them to detect seals from great distances or beneath snow and ice. While their sight and hearing are not as exceptional, polar bears use their sensitive lips and whiskers to investigate their environment.
In the wild, polar bears typically live between 25 and 30 years, though adult mortality ranges from 8 to 16% annually. In captivity, they can live much longer, with the oldest known individual reaching nearly 44 years. The only predators of polar bears are other polar bears and humans. Males may occasionally prey on cubs, which is why mothers often avoid other bears.
Diet
Polar bears are carnivores that rely heavily on the fat-rich blubber of marine mammals to survive in the harsh Arctic. Their primary prey are ringed seals, but they also hunt bearded seals, and occasionally take harp and hooded seals, walruses, and beluga whales when the opportunity arises. In summer, they may scavenge on whale carcasses, reindeer, or bird eggs, and occasionally eat fish, small mammals, berries, or vegetation, though plant matter provides little nutritional value.
Polar bears usually eat only the blubber and skin of seals, leaving the rest of the carcass behind. These leftovers are an important food source for other Arctic animals like foxes. They do not cache or store uneaten meat, unlike some other bear species.
Polar bears use two main hunting techniques:
Still-hunting: They wait silently at a seal’s breathing hole in the ice, striking when the seal surfaces.
Stalking: When a seal is spotted on the ice, the bear may creep low to avoid being seen or swim silently through cracks in the ice to approach. Sometimes, they dive under the ice to surprise seals from below.
They will also break into seal birthing dens to prey on pups. After a kill, polar bears often drag it away from the water and begin feeding immediately. They clean themselves afterward by licking and rinsing their fur.
Reproduction
Polar bears are polygynous and do not form permanent pairs. Mating takes place between March and June, peaking in April and May, when bears gather in areas with abundant seal populations. During this time, males may follow females for long distances and engage in fierce fights with rivals, sometimes resulting in broken teeth and scars. Breeding pairs stay together for only a few days while the female is in estrus, which lasts about three days.
After mating, the fertilized egg undergoes delayed implantation, pausing development until August or September. This allows pregnant females to time birth for the harsh winter. In October or November, each pregnant female digs a maternity den into snowdrifts, usually on land near the coast. The den consists of a narrow tunnel leading to a chamber where the mother enters a hibernation-like dormant state.
Cubs are born between November and January, usually in litters of 1 to 4, with 2 being most common. At birth, cubs are blind, covered in fine fur, and weigh 600 to 900 grams (1.3 to 2.0 pounds). They nurse on rich milk and remain in the den until mid-February to mid-April, when they weigh 10 to 15 kg (22 to 33 lb).
Once outside, the family stays near the den for a few weeks before making the long journey back to the sea ice, where the mother resumes hunting. Cubs stay with their mothers for 2 to 3 years, learning survival skills.
Females typically breed for the first time at age 4 or 5, while males reach sexual maturity around 6, though many do not successfully mate until they are 8 to 10 years old due to competition. Cubs have a mortality rate of 10–30%, and females produce an average of one female cub per adult female every 3 to 4 years.
Population
Between 22,000-31,000 Polar bears are estimated to be roaming near to the North Pole, most being in northern Canada. Currently, this species is classified as Vulnerable (VU) on the IUCN Red List.
Polar bears are still hunted for fur and meat by the Arctic’s native peoples. They are also threatened by drilling for gas and oil, increased shipping activity, and pollution from industrial chemicals. But the major threat is climate change and global warming causing the sea ice to melt earlier in the year and forcing the bears to shore before they have built sufficient fat reserves to survive the period of scarce food. It is suggested that Polar bears could be extinct in the wild within the next 30 years.
Polar bears are the top carnivores of the Arctic. As apex predators, they play a vital role in maintaining the balance of the Arctic ecosystem by regulating seal populations, particularly ringed and bearded seals. The remains of seal kills left behind—often the meat after the blubber has been eaten—provide an important food source for scavengers, including younger, less experienced polar bears and Arctic foxes.
