When pregnant, however, females can weigh as much as 500 kg (1,100 lb). ", Of the 19 recognized polar bear subpopulations, one is in decline, two are increasing, seven are stable, and nine have insufficient data, as of 2017.  The subfamily Ursinae originated approximately 4.2 million years ago. Nonetheless, the biggest polar bear ever found was the male in the northwestern Alaska. ", "Are polar bear populations increasing: in fact, booming?  Maternity dens, used by pregnant females and by females with infants, can also be disturbed by nearby oil exploration and development.  Adult male polar bears weigh 350–700 kg (770–1,500 lb) and measure 2.4–3 metres (7 ft 10 in–9 ft 10 in) in total length. Their concentrations in polar bear tissues continued to rise for decades after being banned, as these chemicals spread through the food chain. Some regulations of hunting did exist. The Inuit refer to the animal as nanook (transliterated as nanuq in the Inupiat language).  Traditional subsistence hunting was on a small enough scale to not significantly affect polar bear populations, mostly because of the sparseness of the human population in polar bear habitat.  Vehicle licence plates in the Northwest Territories in Canada are in the shape of a polar bear, as was the case in Nunavut until 2012; these now display polar bear artwork instead.  Its preferred habitat is the annual sea ice covering the waters over the continental shelf and the Arctic inter-island archipelagos. , Polar bears were hunted heavily in Svalbard, Norway throughout the 19th century and to as recently as 1973, when the conservation treaty was signed. Only with the passage of the treaty did they begin to recover. , Although polar bears are extraordinarily powerful, its primary prey species, the ringed seal, is much smaller than itself, and many of the seals hunted are pups rather than adults. Polar bears sometimes have problems with various skin diseases that may be caused by mites or other parasites.  Bears sometimes swim to Iceland from Greenland—about 600 sightings since the country's settlement in the 9th century AD, and five in the 21st century as of 2016[update]—and are always killed because of their danger, and the cost and difficulty of repatriation. Its hearing is about as acute as that of a human, and its vision is also good at long distances.  Adult bears of either gender occasionally kill and eat polar bear cubs. , The evidence from DNA analysis is more complex.  The hollow guard hairs of a polar bear coat were once thought to act as fiber-optic tubes to conduct light to its black skin, where it could be absorbed; however, this hypothesis was disproved by a study in 1998.  Many Inuit believe the polar bear population is increasing, and restrictions on commercial sport-hunting are likely to lead to a loss of income to their communities. In Russian, it is usually called бе́лый медве́дь (bélyj medvédj, the white bear), though an older word still in use is ошку́й (Oshkúj, which comes from the Komi oski, "bear").  One scientist found that 71% of the Hudson Bay bears had fed on seaweed (marine algae) and that about half were feeding on birds such as the dovekie and sea ducks, especially the long-tailed duck (53%) and common eider, by swimming underwater to catch them. It was killed in 1960 in Kotzebue Sound—leaving scientists to wonder that there may be bigger polar bears out there. Norway is the only country of the five in which all harvest of polar bears is banned.  For subadult bears, which are independent of their mother but have not yet gained enough experience and body size to successfully hunt seals, scavenging the carcasses from other bears' kills is an important source of nutrition. , In general, adult polar bears live solitary lives. It … Ringed seals are born weighing 5.4 kg (12 lb) and grown to an estimated average weight of only 60 kg (130 lb).  This was the case for 40% of cubs there in the early 1980s; however by the 1990s, fewer than 20% of cubs were weaned this young. Unlike brown and black bears, polar bears are capable of fasting for up to several months during late summer and early fall, when they cannot hunt for seals because the sea is unfrozen.  The Polar Bear Specialist Group of the IUCN Species Survival Commission takes the position that "estimates of subpopulation size or sustainable harvest levels should not be made solely on the basis of traditional ecological knowledge without supporting scientific studies.  It banned all importing of polar bear trophies. Indeed, it has been suggested that Arctic peoples' skills in seal hunting and igloo construction has been in part acquired from the polar bears themselves. This status was re-evaluated and confirmed in April 1999, November 2002, and April 2008. , Steven Amstrup and other U.S. Geological Survey scientists have predicted two-thirds of the world's polar bears may disappear by 2050, based on moderate projections for the shrinking of summer sea ice caused by climate change, though the validity of this study has been debated. They were also diving to feed on blue mussels and other underwater food sources like the green sea urchin. In Nunavut, some Inuit have reported increases in bear sightings around human settlements in recent years, leading to a belief that populations are increasing.  The treaty allows hunting "by local people using traditional methods". "The influence of climate variability on polar bear (, "Diet composition of polar bears in Svalbard and the western Barents Sea", "Interactions between polar bears and overwintering walruses in the Central Canadian High Arctic", "Polar bear metabolism cannot cope with ice loss", "Comments on 'Carnivorous walrus and some Arctic zoonoses, "Hudson Bay Post — Goodbye Churchil [sic] Dump", "What to eat now? , More than 600 bears are killed per year by humans across Canada, a rate calculated by scientists to be unsustainable for some areas, notably Baffin Bay.  Sport hunting can bring CDN$20,000 to $35,000 per bear into northern communities, which until recently has been mostly from American hunters. , When the ice floes are at their minimum in the fall, ending the possibility of hunting, each pregnant female digs a maternity den consisting of a narrow entrance tunnel leading to one to three chambers. , According to the World Wildlife Fund, the polar bear is important as an indicator of Arctic ecosystem health. , For the indigenous peoples of the Arctic, polar bears have long played an important cultural and material role. , The Marine Mammal Protection Act of 1972 afforded polar bears some protection in the United States.  Thinner sea ice tends to deform more easily, which appears to make it more difficult for polar bears to access seals. By 2080, they could disappear from Greenland entirely and from the northern Canadian coast, leaving only dwindling numbers in the interior Arctic Archipelago. When walking, the polar bear tends to have a lumbering gait and maintains an average speed of around 5.6 km/h (3.5 mph). The consensus among experts is that the polar bear is the largest, but some believe the Kodiak bear to be larger. , The Inuit and Alaska Natives have many folk tales featuring the bears including legends in which bears are humans when inside their own houses and put on bear hides when going outside, and stories of how the constellation that is said to resemble a great bear surrounded by dogs came into being.  Canada has allowed sport hunters accompanied by local guides and dog-sled teams since 1970, but the practice was not common until the 1980s. Like the brown bear, most ungulate prey of polar bears is likely to be young, sickly or injured specimens rather than healthy adults.  With its body fat providing buoyancy, the bear swims in a dog paddle fashion using its large forepaws for propulsion. The climate change has also adversely affected the overall lifespan of a polar bear. Most maternity dens are in snowdrifts, but may also be made underground in permafrost if it is not sufficiently cold yet for snow. This specimen, when mounted, stood 3.39 m (11 ft 1 in) tall on its hindlegs.  Some estimates of the global population are around 5,000 to 10,000 in the early 1970s; other estimates were 20,000 to 40,000 during the 1980s. Ursus ungavensis Subadults may also be forced to accept a half-eaten carcass if they kill a seal but cannot defend it from larger polar bears.  The polar bear is among the most sexually dimorphic of mammals, surpassed only by the pinnipeds such as elephant seals. , The white coat usually yellows with age. A boar (adult male) weighs around 350–700 kg (772–1,543 lb), while a sow (adult female) is about half that size. , Polar bears diverged from brown bears 400,000–600,000 years ago and have survived past periods of climate fluctuation. Part of the dissension comes from the vagueness of the word “largest.” The answer really depends on how “largest” is defined – Heaviest?  When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time, as polar bears do not 'hibernate' any time of the year.  The evolutionary pressure of polar bear predation on seals probably accounts for some significant differences between Arctic and Antarctic seals. , The range includes the territory of five nations: Denmark (Greenland), Norway (Svalbard), Russia, the United States (Alaska) and Canada. , Because of the way polar bear hunting quotas are managed in Canada, attempts to discourage sport hunting would actually increase the number of bears killed in the short term. International Association for Bear Research and Management (IBA). Under those restrictions, permits from the United States Fish and Wildlife Service were required to import sport-hunted polar bear trophies taken in hunting expeditions in Canada.  Polar bears may attempt to consume almost anything they can find, including hazardous substances such as styrofoam, plastic, car batteries, ethylene glycol, hydraulic fluid, and motor oil. Standing 10 feet, 4 inches and weighing 2,200 pounds, White King's arrival here was the result of a 1957 challenge to find the largest Polar Bear in the Arctic Circle. While the algae is harmless to the bears, it is often a worry to the zoos housing them, and affected animals are sometimes washed in a salt solution, or mild. The permit process required that the bear be taken from an area with quotas based on sound management principles. This hibernation-like state does not consist of continuous sleeping; however, the bear's heart rate slows from 46 to 27 beats per minute. , The International Union for Conservation of Nature, Arctic Climate Impact Assessment, United States Geological Survey and many leading polar bear biologists have expressed grave concerns about the impact of climate change, including the belief that the current warming trend imperils the survival of the polar bear. Yet, they have often been seen playing together for hours at a time and even sleeping in an embrace, and polar bear zoologist Nikita Ovsianikov has described adult males as having "well-developed friendships.  Other provisions included year-round protection of cubs and mothers, restrictions on weapons used and various administrative requirements to catalogue kills. , A widespread legend tells that polar bears cover their black noses with their paws when hunting. Their southernmost range is near the boundary between the subarctic and humid continental climate zones.  Although ungulates are not typical prey, the killing of one during the summer months can greatly increase the odds of survival during that lean period.