Introduction to the Polar Bears
The polar bear (Ursus maritimus), sometimes known as the huge white northern bear (family Ursidae), is widespread across the Arctic region. Polar bears travel enormous distances across huge lonely stretches, usually on drifting oceanic ice floes, in pursuit of seals, their principal diet. The polar bear, with a brown bear subspecies known as the Kodiak bear, is the largest and most powerful animal on Earth. It has no natural predators or fear of people, making it a highly hazardous species.
Physical Characteristics and Adaptations
Polar bears are bulky, with a long neck, a tiny head, short, rounded ears, and a short tail. The male, significantly larger than the female, weighs 410 to 720 kg (900 to 1,600 pounds). The tail measures 7–12 cm (3-5 inches) in length. Sunlight may permeate through the thick fur, and the heat is absorbed by the bear’s dark skin. A layer of fat serves as insulation beneath the skin. The large feet have hairy soles to protect and insulate while also allowing for mobility across the ice, as does the uneven skin on the soles of the feet, which helps to prevent slippage. Strong, pointed claws are also useful for getting traction, digging through ice, and killing prey.
Diet and Hunting Behavior
Polar bears are solitary and primarily carnivorous, eating on ringed seals, bearded seals, and other pinnipeds. The bear hunts seals lying on the ice ambushes them near breathing holes, and excavates young seals from snow shelters where they are born. Polar bears enjoy ice that is periodically fractured by wind and sea currents because it allows seals to access both air and water. Polar bears are superb swimmers, and they have been known to kill beluga whales. The polar bear swims using only its front limbs, a unique aquatic adaptation found in no other four-legged mammal. They are both opportunistic and predatory, eating dead fish, stranded whale corpses, and garbage near human settlements.
Reproduction and Life Cycle
Mating occurs in the spring, and implantation of the fertilized ovum is delayed. Including the delay, gestation can take 195-265 days, and one to four cubs, usually two, are born in a winter lair of ice or snow. Cubs weigh less than 1 kilogram at birth and are not weaned until around two years of age. Young polar bears can die from malnutrition or be murdered by adult males, hence female polar bears are fiercely protective of their offspring when adult males are present.
Young stay with their mothers until they attain sexual maturity. Females reproduce for the first time between the ages of four and eight, and then every two to four years. Males mature around the same age as females, but they do not reproduce until a few years later. Adult polar bears do not have any natural predators, but walruses and wolves can kill them. Longevity in the wild is 25 to 30 years, however, in captivity, several polar bears have lived to be over 35 years old.
Human Interaction and Impact
Humans are most likely responsible for the majority of polar bear deaths, as they hunt and kill nuisance animals near towns. They have been known to kill humans. They are mostly hunted by Inuit people for their hides, tendons, fat, and flesh. Indigenous cultures eat polar bear meat, however the liver is inedible and generally deadly due to its high vitamin A level.
Conservation Status and Future Challenges
By 2020, there were an estimated 22,000 to 31,000 polar bears in the wild. The International Union for Conservation of Nature (IUCN) has classified the polar bear as a vulnerable species since 2006, and the United States government has listed it as a threatened species since 2008, owing in large part to the effects of global warming, which is reducing Arctic sea ice coverage. Polar bears find their ideal habitat on sea ice.
Population models indicate greater rates of famine as a result of prolonged ice-free seasons and a decrease in mating success, as sea ice fragmentation may limit male-female encounter rates. Ecological studies suggest that as sea ice coverage has declined, polar bears have had to spend more time hunting for berries and seabird eggs, which are lower-quality items that require more work to obtain. Given the cumulative threats to the species, model projections indicate that polar bear populations will have decreased by one-third by 2050.