Polar bear

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Polar bear
Conservation status
Vulnerable (IUCN) [1]
Scientific classification
Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Family: Ursidae Genus: Ursus Species: U. maritimus
Binomial name
Ursus maritimus Phipps, 1774
Polar bear range
Synonyms
Ursus eogroenlandicus Ursus groenlandicus Ursus jenaensis Ursus labradorensis Ursus marinus Ursus polaris Ursus spitzbergensis Ursus ungavensis Thalarctos maritimus

The polar bear (Ursus maritimus) is a bear native to the Arctic. The world's largest land carnivore, an adult male weighs around 300–600 kg (660–1320 lb), while an adult female is about half that size. Although it is closely related to the brown bear, it has evolved to occupy a narrow ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting seals.^[2] It feeds almost exclusively on seals, although it is an opportunistic feeder and will eat almost anything if hungry. It is the apex predator within its range.^[3]

The polar bear is classified as a vulnerable species. Of the 19 recognized polar bear subpopulations, 5 are declining, 5 are stable, 2 are increasing, and 7 have insufficient data.^[4][5] For decades, unrestricted hunting raised international concern for the future of the species; populations have rebounded after controls and quotas began to take effect.

The IUCN now lists global warming as the most significant threat to the polar bear, primarily because the melting of its sea ice habitat reduces its ability to find sufficient food. The IUCN states, "If climatic trends continue polar bears may become extirpated from most of their range within 100 years."^[1] The U.S. Fish and Wildlife Service formally proposed listing the polar bear as a threatened species on January 7, 2007. A final decision was due on January 7, 2008 but has been delayed^[6].

Contents 1 Naming and etymology 2 Taxonomy and evolution 3 Population and distribution 4 Habitat 5 Biology and behavior 5.1 Physical characteristics 5.2 Hunting and diet 5.3 Behavior 5.4 Reproduction and lifecycle 5.4.1 Maternity denning and early life 5.4.2 Later life 5.5 Health 6 Exploitation 6.1 Indigeneous people 6.2 History of commercial harvest 6.3 Contemporary regulations 6.3.1 Russia 6.3.2 Greenland 6.3.3 Canada and the United States 7 Conservation status, efforts and controversies 7.1 Global warming 7.2 Pollution 7.3 Controversy over species protection 7.4 Listing under the U.S. Endangered Species Act 8 Polar bears and human culture 8.1 Indigenous folklore 8.2 As symbols and mascots 8.3 In literature 9 See also 10 References 11 Notes 12 External links

Naming and etymology

Constantine John Phipps was the first to describe the polar bear as a distinct species.^[1] He chose the scientific name Ursus maritimus, the Latin for 'maritime bear',^[7] due to the animal's native habitat. The Inuit refer to the animal as Nanuk (occasionally rendered as Nanook, or Nanuuq in the Inupiat language).^[8][9] Likewise it is Nanuuk in Siberian Yupik, and Umka in the Chukchi language. In Russian, the polar bear is commonly called "Белый Медведь" - (Bely Medved = White Bear), though an older still familiar word is Ошкуй - Oshkuy, which comes from the Komi Oski ("Bear"). ^[10]

The polar bear was previously considered to be in its own genus, Thalarctos.^[11] However, evidence of hybrids between polar bears and brown bears, and of the relatively recent evolutionary divergence of the two species, does not support the establishment of this separate genus, and the accepted scientific name is now therefore Ursus maritimus, as Phipps originally proposed.^[12]

Taxonomy and evolution

The bear family, ursidae, is believed to have split off from other carnivorans about 38 million years ago. The ursinae subfamily originated approximately 4.2 million years ago. According to both fossil and DNA evidence, the polar bear diverged from the brown bear, Ursus arctos, roughly 200 thousand years ago. The oldest known polar bear fossil is less than 100 thousand years old. Fossils show that between 10 and 20 thousand years ago, the polar bear's molar teeth changed significantly from those of the brown bear. Polar bears are thought to have diverged from a population of brown bears that became isolated during a period of glaciation in the Pleistocene.^[13]

More recent genetic studies have shown that some clades of brown bear are more closely related to polar bears than to other brown bears,^[14] meaning that the polar bear is not a true species according to some species concepts.^[15] In addition, polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids,^[13][16] indicating that they have only recently diverged and are genetically similar.^[17] However, as neither species can survive long in the other's ecological niche, and with distinctly different morphology, metabolism, social and feeding behaviors, and other phenotypic characteristics, the two bears are generally classified as separate species.^[17]

Polar bears still have a vestigial hibernation induction trigger in their blood, but they do not hibernate in the winter as the brown bear does. Only female polar bears enter a dormant state (referred to as "denning") during pregnancy, though their body temperature does not decrease during this period as it would for a typical mammal in hibernation.^[18][19]

When the polar bear was originally documented, two subspecies were identified: Ursus maritimus maritimus by Constantine J. Phipps in 1774, and Ursus maritimus marinus by Peter S. Pallas in 1776.^[20] This distinction has since been invalidated. One fossil subspecies has been identified. Ursus maritimus tyrannus—descended from Ursus arctos—became extinct during the Pleistocene. U.m. tyrannus was significantly larger than the living subspecies.^[13]

Population and distribution

The polar bear is a circumpolar species that is found throughout the Arctic Ocean and adjacent seas. While they are rare north of 88°, there is evidence that they range all the way across the Arctic, and as far south as James Bay in Canada. They can occasionally drift widely with the sea ice, and there have been anecdotal sightings as far south as Berlevag village on the Norwegian mainland, the Kuril Islands in the Sea of Okhotsk. It is difficult to estimate a global population of polar bears since much of the range has been poorly studied, but biologists estimate that there about 20,000-25,000 polar bears worldwide.

The distribution of polar bears is not uniform and there are 19 generally recognized discrete subpopulations.^[5][4] The subpopulations display seasonal fidelity to geographic area but DNA studies show that they are not reproductively isolated.^[21] The thirteen North American subpopulations range from the Beaufort Sea south to Hudson Bay and east to Baffin Bay in Western Greenland and account for about 70% of the global population. The Eurasian population is broken up into the East Greenland, Barents Sea, Kara Sea, Laptev Sea, and Chukchi Sea subpopulations, though there is considerable uncertainty about the structure of these populations due to limited mark-recapture data.

The range includes the territory of five nations: Denmark (Greenland), Norway (Svalbard), Russia, USA (Alaska) and Canada. These five nations are the signatories of the 1973 International Agreement for the Conservation of Polar Bears which mandates cooperation on research and conservations efforts throughout the polar bear's range.

Habitat

The polar bear is often regarded as a marine mammal because it spends many months of the year at sea.^[18] Its preferred habitat is the annual sea ice (that is, ice that melts for part of the year) covering the waters over the continental shelf. These areas have relatively high biological productivity in comparison to other parts of the Arctic. The polar bear tends to frequent areas of open water, such as polynyas, to hunt the seals that make up most of its diet.^[22] Polar bears are therefore found primarily along the perimeter of the polar ice pack, rather than in the Polar Basin close to the North Pole where the density of seals is low.^[23]

In much of the Arctic, areas of water appear and disappear throughout the year as the weather changes. Seals migrate in response to these changes, and polar bears must follow their prey.^[24] In Hudson Bay, James Bay, and some other areas, the ice melts completely each summer (an event often referred to as "ice-floe breakup"), forcing polar bears to go onto land and wait through the months until the next freeze-up.^[24]

Biology and behavior

Physical characteristics

Polar bears are the largest living land carnivores. Males are generally 25–45% larger than females.^[25] Most adult males weigh 350–650 kg (770–1500+ lb) and measure 2.5–3.0 m (8.2–9.8 ft) in length. Adult females are roughly half the size of males and normally weigh 150–250 kg (330–550 lb), measuring 2–2.5 m (6.6–8.2 ft), but double their weight during pregnancy.^[18][26] The great difference in body size makes the polar bear among the most sexually dimorphic of mammals, surpassed only by the eared seals.^[27] The largest polar bear on record, reportedly weighing 1002 kg (2200 lb), was a male shot at Kotzebue Sound in northwestern Alaska in 1960.^[28]

Compared with its closest relative, the brown bear, polar bears have a more elongated body build and a longer skull and nose.^[17] As predicted by Allen's rule for a northerly animal, the legs are stocky and the ears and tail (7–12 cm (2.8–4.8 in)^[25] are small.^[17] However, the feet are very large: 36 cm (12 in) across in an adult, to distribute load when walking on snow or thin ice (as with snowshoes).^[29] Stiff hairs on the pads of the paws provide insulation and traction on the ice. A polar bear's claws are short and stocky compared to a brown bear's.^[17] Despite a recurring internet meme that all polar bears are left-handed,^[30][31] there is no scientific evidence to support this claim. ^[32]

The 42 teeth of a polar bear reflect its highly carnivorous diet.^[17] The cheek teeth are smaller and more jagged than in the brown bear, and the canines are larger and sharper.^[17] The dental formula is:^[17]

3.1.4.2

3.1.4.3

Polar bear fur consists of a layer of dense underfur and an outer layer of guard hairs, which appear white to tan but are actually translucent.^[29] The guard hair is 5–15 cm (2–6 in) over most of the body.^[33] Polar bears are superbly insulated by their 10 cm (4 in) of blubber,^[29] their hide and their fur; they overheat at temperatures above 10 °C (50 °F), and are nearly invisible under infrared photography.^[18]

Polar bears gradually molt from May to August,^[34] but, unlike other Arctic mammals, they do not shed their coat for a darker shade to camouflage themselves in the summer conditions. 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 theory was disproved by recent studies.^[35] The white coat usually yellows with age. When kept in captivity in warm, humid conditions, it is not unknown for the fur to turn a pale shade of green due to to algae growing inside the guard hairs. ^[36] Males have significantly longer hairs on their forelegs, that increase in length until the bear reaches 14 years of age. The male's ornamental foreleg hair is thought to attract females, serving a similar function to the lion's mane.^[27]

The polar bear has an extremely well-developed sense of smell, being able to detect seals nearly a mile away and buried under three feet of snow.^[37] Its hearing is about as acute as that of a human, and its vision is also good at long distances.^[37]

Polar bears are excellent swimmers and have been seen in open Arctic waters as far as 60 miles (100 km) from land. Their 12 cm (5 in) layer of fat adds buoyancy in addition to insulating them from the cold.

Hunting and diet

The polar bear is the most carnivorous member of the bear family; 95% of its diet consists of ringed and bearded seals.^[39] The Arctic is home to millions of seals, which become prey when they surface in holes in the ice in order to breathe, or when they haul out on the ice to rest.^[38] The polar bear's most common hunting method is called still-hunting:^[40] The bear uses its excellent sense of smell to locate a seal breathing hole, and crouches nearby in silence for a seal to appear.^[38] When the seal exhales, the bear smells its breath, reaches into the hole with a forepaw, and drags it out onto the ice.^[38] The polar bear kills the seal by biting its head to crush its skull.^[38] The polar bear also hunts by stalking seals resting on the ice: Upon spotting a seal, it walks to within 100 yards, and then crouches. If the seal does not notice, the bear creeps to within 30 or 40 feet of the seal and then suddenly rushes forth to attack.^[38] A third method of hunting seals is to raid the snow caves created by female seals which are about to give birth.^[40]

Mature bears tend to eat only the skin and blubber of the seal, whereas younger bears consume the protein-rich red meat.^[38] For subadult bears who 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. 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 an enormously powerful predator. It can kill an adult walrus, although it rarely attempts to do so as a walrus can be twice the bear's weight.^[41] However, most terrestrial animals can outrun the polar bear on land, most marine animals can outswim it in open water, and polar bears overheat quickly. Polar bears subsist almost entirely on seals and walrus calves taken from the sea-ice and on the carcasses of dead adult walruses or whales. Some populations, where sea-ice is unavailable during summer and early fall, live off fat reserves for months at a time.^[18] Polar bears have also been observed to eat a wide variety of other wild foods, including muskox, reindeer, birds, eggs, rodents, shellfish, crabs, and other polar bears. They may also eat plants, including berries, roots, and kelp, however none of these are a significant part of their diet.^[41] The polar bear's biology is specialized to require large amounts of fat from marine mammals, and it cannot derive sufficient caloric intake from terrestrial food.^[42][43]

Being both curious animals and scavengers,^[44][41] polar bears will investigate and consume garbage where they come into contact with humans.^[41] This was documented at the dump in Churchill, Manitoba before its closure.^[45] 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.^[41][44] The Churchill dump was closed in 2006 to protect the bears, and waste is now recycled or transported to Thompson, Manitoba.^[46]

Behavior

Polar bears are aggressive and inquisitive, and, as such, potentially dangerous to humans. Unlike most other bears, wild polar bears are poorly habituated to humans and will quickly assess any animal they encounter as potential prey. Males are normally solitary except for mating season, although females are usually social towards one another.

Reproduction and lifecycle

Polar bears have a polygynous mating system, however partners stay together and mate repeatedly for an entire week.^[47] Adult males often have broken teeth and scars from intense fighting with other males over mating rights.^[48] Courtship and mating take place on the sea ice in April and May; the mating ritual induces ovulation in the female.^[47] The fertilized egg then remains in a suspended state until August or September.

During these four months, recently-mated females eat prodigious amounts of food in preparation for pregnancy, gaining at least 200 kg (440 lb) and often more than doubling their body weight.^[48]

Maternity denning and early life

When the ice floes break up 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.^[48] Most maternity dens are in snowdrifts, but may also be made underground if it is not sufficiently cold yet for snow.^[48] In most populations, maternity dens are situated on land a few kilometers from the coast, and populations tend to reuse the same denning areas each year.^[49] In the den, she enters a dormant state similar to hibernation. This hibernation-like state does not consist of continuous sleeping, however the bear's heart rate slows from 46 to 27 beats per minute.^[50]

Between November and February, cubs are born blind, covered with a light down fur, and weighing less than 0.9 kg (2 lb).^[47] On average, each litter has two cubs.^[48] The family remains in the den until mid-February to mid-April, with the mother maintaining her fast while nursing her cubs on a fat-rich milk.^[48]. By the time the mother then breaks opens the entrance to the den, her cubs weigh about 10 to 15 kg (25 to 30 lb).^[48] For about 12 to 15 days, the family spends time outside the den while remaining in its vicinity, the mother grazing on vegetation while the cubs become used to walking and playing.^[48] Then they begin the long walk to from the denning area to the sea ice, where the mother can once again catch seals.^[48] Depending on the timing of ice-floe breakup in the fall, she may have fasted for up to eight months.^[48]

Cubs may fall prey to wolves, to adult male polar bears, or to starvation. Female polar bears are noted for both their affection towards their offspring, and their valiance in protecting them. In Alaska, 42% of cubs now reach 12 months of age, down from 65% 15 years ago.^[51] In most areas, cubs are weaned at two and a half years of age,^[48] when the mother chases them away or abandons them. The western coast of Hudson Bay is unusual in that its female polar bears sometimes wean their cubs at only one and a half years.^[48] This was the case for 40% of cubs in western Hudson Bay in the early 1980s, however by the 1990s, fewer than 20% of cubs were weaned this young.^[52]

Later life

Females begin to breed at the age of four years in most areas, and five years in the Beaufort Sea area.^[48] Males usually reach sexual maturity at six years, however as competition for females is fierce, many do not breed until the age of eight or ten.^[48] A study in Hudson Bay indicated that both the reproductive success and the maternal weight of females peaked in their mid-teens.^[53] Polar bears rarely live beyond 25 years.^[54] The oldest wild bear on record died at the age of 32, and the oldest captive at 41.^[54]

Health

The bears sometimes have problems with various skin diseases which may be caused by mites or other parasites. The bears are especially susceptible to Trichinella, a parasitic roundworm they contract through cannibalism.^[55] Sometimes excess heavy metals have been observed, as well as ethylene glycol (antifreeze) poisoning. Bears exposed to oil and petroleum products lose the insulative integrity of their coats, forcing metabolic rates to dramatically increase to maintain body heat in their challenging environment. Bacterial Leptospirosis, rabies and Morbillivirus have been recorded. The bears are thought by some to be more resistant than other carnivores to viral disease.^{[citation needed]} The pollutant effect on the bears' immune systems, however, may end up decreasing their ability to cope with the naturally present immunological threats they encounter, and in such a challenging habitat even minor weaknesses can lead to serious problems and rapid mortality.

Exploitation

Indigeneous people

Polar bear have long provided important raw materials for Arctic peoples, including the Inuit, Yupik, Chukchi, Nentets, Russian Pomors and others. Almost all parts of captured animals was used.^[56] The fur was used in particular to sew pants and, by the Nenets, to make galoshes-like outer footwear called tobok; the meat is edible, despite some risk of trichinosis; the fat was used in food and as a fuel for lighting homes, alongside seal and whale blubber; sinews were used as thread for sewing clothes, the gall bladder and sometimes heart were dried and powdered for medicinal purposes; the large canines were highly valued as talismans.^[57] Only the liver was not used, as its high concentration of vitamin A is poisonous.^[58] Indeed, hunters make sure to either toss the liver into the sea or bury it in order to spare their dogs from potential poisoning.^[57] 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.^[59]

History of commercial harvest

In Russia, polar bear furs were already being commercially traded in the 14th century, though it was of relatively low value compared to arctic fox or even reindeer fur.^[57] The growth of the human population in the Eurasian arctic in the 16th and 17th century, together with the advent of firearms and increasing trade, dramatically increased the harvest of polar bears.^[18][60]. However, since polar bear fur has always played a marginal commercial role, data on the historical harvest is fragmentary. It is known, for example, that already in the winter of 1784/1785 Russian Pomors on Spitzbergen harvested 150 polar bears on Magdalena fjord.^[57] In the early 20th century, Norwegian hunters were harvesting 300 bears a year at the same location. Estimates of total historical harvest suggest that from the beginning of the 18th century, roughly 400-500 animals were being harvested annually in northern Eurasia, reaching a peak of 1,300 to 1,500 animals in the early 20th century, and falling off as the numbers began dwindling.^[57]

In the first half of the 20th century, mechanized and overpoweringly efficient methods of hunting and trapping came into use in North America as well.^[61] Polar bears were chased from snowmobiles, icebreakers, and airplanes, the latter practice described in a 1965 New York Times editorial as being "about as sporting as machine gunning a cow."^[61] The numbers taken grew rapidly in the 1960s, peaking around 1968 with a global total of 1,250 bears that year.^[62]

Contemporary regulations

Concerns over the future survival of the species led to the development of international regulations on polar bear hunting. Norway passed a series of increasingly strict regulations from 1965 to 1973, and has completely banned hunting since then. The Soviet Union banned all commercial hunting outright in 1955. Canada began imposing hunting quotas in 1968. The U.S. began regulating in 1971 and adopted the Marine Mammal Protection Act in 1972. In 1973, the International Agreement on the Conservation of Polar Bears, also known as the Oslo Agreement, was signed by all five nations whose territory is inhabited by polar bears. Although the agreement is not enforceable in itself, member countries agreed to place restrictions on recreational and commercial hunting, completely ban hunting from aircraft and icebreakers, and conduct further research.^[63] The treaty allows hunting "by local people using traditional methods," although this has been liberally interpreted by member nations.

Russia

The Soviet Union declared a complete protection in 1955,^[18] but allows hunting by the indigenous people on the basis that it is part of their culture. It signed the "Agreement between the Government of the United States of America and the Government of the Russian Federation on the Conservation and Management of the Alaska-Chukotka Polar Bear Population" in October 2000.

Greenland

In Greenland, restrictions for the species were first introducted in 1994 and expanded by executive order in 2005.^[5] Until 2005, Greenland placed no limit on hunting by indigenous people. It imposed a limit of 150 for 2006. It also allowed recreational hunting for the first time.^[64] Other provisions included year-round protection of cubs and mothers, restrictions on weapons used, and various administrative requirements to catalogue kills.^[5]

Canada and the United States

About 500 bears are killed per year by humans across Canada,^[65] a rate believed by scientists to be unsustainable for some areas, notably Baffin Bay.^[4] Canada has allowed sport hunters accompanied by local guides and dog-sled teams since 1970,^[66] but the practice was not common until the 1980s.^[67] The guiding of sport hunters provides meaningful employment and an important source of income for native communities in which economic opportunities are few.^[68] Sport hunting can bring CDN$20,000 to $35,000 per bear into northern communities, mostly from American hunters.^[69]

The 1972 United States Marine Mammal Protection Act prohibits the harassment, injuring or killing of any marine mammal species, including polar bears. It also prohibits the importation of products made from polar bears. In 1994, legislation was modified to allow issuing import permits for sport-hunted polar bear trophies, thereby allowing Americans to bring back trophies from hunting expeditions in Canada. The permits are issued by the U. S. Fish and Wildlife Service, which requires that the bear be taken from an area with quotas based on sound management principles.^[70] Since 1994, more than 800 sport-hunted polar bear trophies have been imported into the U.S.^[71] In 2007, the proposed Polar Bear Protection Act was introduced to reverse the 1994 legislation and ban the importation of dead polar bears; the proposal was defeated.^[72][73]

Ironically, 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.^[68] Canada allocates a certain number of permits each year to sport and subsistence hunting, and those that are not used for sport hunting are re-allocated to native subsistence hunting. Approximately 50% of sport hunters with permits actually kill a polar bear, whereas for subsistence hunters the success rate is 100%.^[68]

The territory of Nunavut accounts for 80% of Canadian kills.^[65] The Nunavut government has condemned the American initiative to grant threatened status to polar bears,^[74] and northern residents are strongly concerned about it.^[75] In 2005, the government of Nunavut increased the quota from 400 to 518 bears,^[76] despite protests from some scientific groups.^[77] While most of that quota is hunted by the indigenous Inuit people, a growing share is sold to recreational hunters. (0.8% in the 1970s, 7.1% in the 1980s, and 14.6% in the 1990s)^[67] Nunavut polar bear biologist, M.K. Taylor, who is responsible for polar bear conservation in the territory, insists that bear numbers are being sustained under current hunting limits.^[78] The Government of the Northwest Territories maintain their own quota of 72–103 bears within the Inuvialuit communities of which some are set aside for sports hunters.

Conservation status, efforts and controversies

The World Conservation Union (IUCN) listed polar bears as a vulnerable species in May 2006.^[79] It cited a "suspected population reduction of >30% within three generations (45 years)", due primarily to global warming.^[1] Other risks to the polar bear include pollution in the form of toxic contaminants, conflicts with shipping, stresses from recreational polar-bear watching, and oil and gas exploration and development.^[1] The IUCN also cited a "potential risk of over-harvest" through legal and illegal hunting.^[1]

Global warming

The IUCN, Arctic Climate Impact Assessment, and many leading polar bear biologists have expressed grave concerns about the impact of global warming, including the belief that the species is unlikely to survive if current warming trends continue.^{[80][81][82][83][49][84]}

The key danger to polar bears is malnutrition or starvation due to habitat loss: Polar bears hunt seals from a platform of sea ice. Rising temperatures cause the sea ice to melt earlier in the year, driving the bears to shore before they have built sufficient fat reserves to survive the period of scarce food in the late summer and early fall.^[52] Reduction in sea-ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning.^[85] To carry a pregnancy to term and nurse a young litter, an adult female must gain at least 200 kg before entering her maternity den.^[48] Insufficient nourishment leads to lower reproductive rates in adult females and lower survival rates in cubs and juvenile bears, in addition to poorer body condition in bears of all ages.^[49] The effects of global warming are most profound in the southern part of the polar bear's range, and this is indeed where significant degradation of local populations has been observed.^[84] A study by the Canadian Wildlife Service indicated that between 1981 and 1988, shorter periods of sea-ice cover led to a 22% decline in the Hudson Bay subpopulation.^[52][86]

The United States Geological Survey stated in November 2006, that the Arctic shrinkage in the Alaskan portion of the Beaufort Sea has led to a higher death rate for polar bear cubs.^[51] In Alaska, changes in sea ice conditions have already forced pregnant polar bears to dig their maternity dens on land rather than on pack ice.^[87] Recently, polar bears in the Arctic have undertaken longer than usual swims to find prey, resulting in four recorded drownings in the unusually large ice pack regression of 2005.^[85]

The United States Geological Survey predicts two-thirds of the world's polar bears will disappear by 2050, based on moderate projections for the shrinking of summer sea ice caused by global warming.^[88] The bears would disappear from Europe, Asia, and Alaska, and be depleted from the Arctic archipelago of Canada and areas off the northern Greenland coast. By 2080, they would disappear from Greenland entirely and from the northern Canadian coast, leaving only dwindling numbers in the interior Arctic archipelago.^[88] The latest estimate of the IUCN is that 5 out of 19 subpopulations are declining.^[5]

Predictions vary on the extent to which polar bears could adapt to climate change by switching to terrestrial food sources. Mitchell Taylor, the Nunavut Government Manager of Wildlife Research, wrote to the U.S. Fish and Wildlife Service arguing that local studies are insufficient evidence for global protection at this time. The letter stated, "At present, the polar bear is one of the best managed of the large Arctic mammals. If all Arctic nations continue to abide by the terms and intent of the Polar Bear Agreement, the future of polar bears is secure…. Clearly polar bears can adapt to climate change. They have evolved and perisisted for thousands of years in a period characterized by fluctuating climate."^[78] Ken Taylor, deputy commissioner for Alaska's Department of Fish and Game, has said, "I wouldn't be surprised if polar bears learned to feed on spawning salmon like grizzly bears."^[68] However, many scientists consider these theories to be naive.^[68]; it is noted that black and brown bears at high latitudes are smaller than elsewhere, because of the scarcity of terrestrial food resources.^[89] The IUCN wrote:

“

Polar bears exhibit low reproductive rates with long generational spans. These factors make facultative adaptation by polar bears to significantly reduced ice coverage scenarios unlikely. Polar bears did adapt to warmer climate periods of the past. Due to their long generation time and the current greater speed of global warming, it seems unlikely that polar bear will be able to adapt to the current warming trend in the Arctic. If climatic trends continue polar bears may become extirpated from most of their range within 100 years.[1]

”

Pollution

Polar bears accumulate high levels of artificial halocarbons such as PCBs and pesticides because of their diet. Their position at the top of the food pyramid tends to concentrate pollutants, particularly halocarbons because of their lipophilicity: halocarbons are soluble in the blubber which makes up the bulk of the polar bear's diet. Halocarbons are known to be toxic to other animals because they mimic hormone chemistry, and biomarkers such as immunoglobulin G and retinol suggest similar effects on polar bears. The overall significance to population health is uncertain because of unique features of polar bear biology such as summertime fasting. PCBs have received the most study, and they have been associated with birth defects and immune system deficiency.^[90] Polar bears in Svalbard have the highest concentrations of PCBs, and biologists suggest this may explain the high incidence of hermaphroditic bears in the area.^[91]

The relevant chemicals have been classified as persistent organic pollutants by the United Nations, with the aim of discouraging their production. The most notorious of these, PCBs, DDT and others, have been banned, but their concentrations in polar bear tissues continued to rise for decades after the ban as these chemicals spread upwards on the food pyramid. The most recent data now indicates a decreasing trend.^[92]

Controversy over species protection

Warnings about the future of the polar bear are often contrasted with the fact that worldwide population estimates have increased over the past 50 years and are relatively stable today. ^[93][94] Some estimates of the global population are around 5,000–10,000 in the early 1970s^[95][96]; other estimates were 20,000–40,000 during the 1980s.^[18] Current estimates put the global population at between 20,000 and 25,000.^[5]

There are several reasons for the apparent discordance between past and projected population trends: Estimates from the 1950s and 1960s were based on stories from explorers and hunters rather than on scientific surveys.^[97][98] Second, controls of harvesting were introduced that allowed this previously-overhunted species to recover.^[97] Third, the recent effects of global warming have affected sea ice abundance in different areas to varying degrees.^[97] Long-term studies of local populations of polar bears show they have been shrinking in the Western Hudson Bay and Baffin Bay areas, and are under stress in the Southern Beaufort Sea area.^[4] In the Western Hudson Bay region, for example, there were an estimated 1,194 polar bears in 1987, and 935 in 2004^[86]–though there were an estimated 500 polar bears there in 1981.^[99]

Modern methods of tracking polar bear populations have been implemented only since the mid-1980s, and are extremely expensive and difficult to perform consistently over a large area.^[68] The most accurate counts require flying a helicopter in the difficult Arctic climate to find bears, shooting a tranquilizer dart at the bear to sedate it, and then tagging the bear.^[68] Some Inuit are skeptical of conservation concerns in part because of increases in bear sightings near settlements in recent years.^[80] Scientists have responded by noting that hungry bears may be congregating around human settlements, leading to the illusion that populations are higher than they actually are.^[68]

Listing under the U.S. Endangered Species Act

In February 2005, the Center for Biological Diversity petitioned the U.S. Fish and Wildlife Service to list the bears as as threatened species under the Endangered Species Act.^[100] The agency did not respond to the petition, despite being required to do so within 90 days.^[100] On 14 December 2006 the Center for Biological Diversity, Greenpeace and the Natural Resources Defense Council filed a successful lawsuit to compel a decision.^[101]

On January 9, 2007, the U.S. Fish and Wildlife Service formally proposed to list the polar bear as a threatened species. A final decision was due on January 9, 2008, at which time the agency said it needed another month. On March 7 2008, the inspector general of the U.S. Interior Department began a preliminary investigation into why the decision had been delayed for nearly two months.^[102] The investigation is in response to a letter signed by six environmental groups that U.S. Fish and Wildlife Director Dale Hall violated the agency's scientific code of conduct by delaying the decision unnecessarily, allowing the government to proceed with an auction for oil and gas leases in the Alaska's Chukchi Sea, an area of key habitat for polar bears.^[102] The auction took place in early February 2008.^[102] Hall denied any political interference in the decision and said that the delay was needed to make sure the decision was in a form easily understood.^[102]

If listed, the polar bear would be only the third species, after the elkhorn coral and the staghorn coral protected under the Endangered Species Act due to global warming.

Polar bears and human culture

Indigenous folklore

For the indigenous peoples of the Arctic polar bears have long played an important cultural and material role.^[56][57] Polar bear remains have been found at hunting sites dating to 2,500 to 3,000 years ago^[59] and 1500 year old cave paintings of polar bears have been found in Chukotka.^[57] Indeed, it has been suggested that Arctic peoples' skills in seal hunting and snowhouse construction has been in part acquired from the polar bears themselves.^[57]

The Inuit have many folk tales featuring the bears including legends in which the bears shed their skins to become men and stories of how the constellation which is said to be a great bear surrounded by dogs came into being.

Among the Chukchi and Yupik of eastern Siberia, there was a longstanding shamanistic ritual of "thanksgiving" to the hunted polar bear. After hunting a polar bear, its head and skin were removed and cleaned and traditionally brought into the home, there was a feast in the hunting camp in its honor. In order to appease the spirit of the bear, there were traditional song and drum music and the skull would be ceremonially fed and offered a pipe.^[103] Only once the spirit was appeased, would the skull be separated from the skin, taken beyong the bounds of the homestead, and placed in the ground, facing North.^[57] Many of these traditions have faded somewhat in time, especially in light of the total hunting ban in the Soviet Union since 1955.

The Nenets of north central Siberia placed particular value on the talismanic power of the prominent canines. They were traded in the villages of the lower Yenisei and Khatanga rivers to the forest-dwelling peoples further south, who would sew them into their hats as protection against brown bears. It was believed that the "little nephew" (the brown bear) would not dare to attack a man wearing the tooth of its powerful "big uncle" (the polar bear).^[57] The skulls of killed polar bears were buried to specific sacred sites and construct altars, called sedyangi, out of the skulls. Several such sites have been preserved on the Yamal Peninsula.^[57]

As symbols and mascots

Their distinctive appearance and their association with the Arctic have made polar bears popular icons, especially in those areas where they are native. The Canadian 2-dollar coin features the image of a polar bear and both the Northwest Territories and Nunavut in Canada have a licence plate in the shape of a polar bear. The A polar bear is the mascot of Bowdoin College in Maine and was chosen as mascot for the 1988 Winter Olympics held in Calgary.

Companies such Coca-Cola, Polar Beverages, Nelvana, Bundaberg Rum and Good Humor-Breyers have used images of the polar bear in advertising,^[104] while Fox's Glacier Mints have featured a polar bear named Peppy as the brand mascot since 1922.

In literature

Polar bears are also popular in fiction, particularly in books aimed at children or young adults. The book, The Polar Bear Son, is adapted from a traditional Inuit tale.^[105] They feature prominently in North Child by Edith Pattou, and the Raymond Briggs book The Bear. The panserbjørne of Philip Pullman's fantasy trilogy His Dark Materials are sapient, dignified polar bears who exhibit anthropomorphic qualities. They feature prominently in the 2007 film adaptation of the The Golden Compass, while the TV series Lost has shown polar bears on a mysterious tropical island.

See also

• Arctic shrinkage
• Arctic National Wildlife Refuge
• Knut (polar bear)
• USS Connecticut (SSN-22)

References

• Bruemmer, Fred (1989). World of the Polar Bear. Toronto, ON: Key Porter Books. ISBN 1-55013-107-9. 
• Matthews, Downs (1993). Polar Bear. San Francisco, CA: Chronicle Books. ISBN 0-8118-0050-X. 
• Hemstock, Annie (1999). The Polar Bear. Manakato, MN: Capstone Press. ISBN 0-7368-0031-X. 
• Lockwood, Sophie (2006). Polar Bears. Chanhassen, MN: The Child's World. ISBN 1-59296-501-6. 
• Rosing, Norbert (1996). The World of the Polar Bear. Willowdale, ON: Firefly Books Ltd.. ISBN 1-55209-068-X. 

Notes

External links

• Photos, facts, videos from Polar Bears International which funds population, preservation and DNA studies of the polar bear
• ARKive - images and movies of the polar bear (Ursus maritimus)
• Smithsonian National Museum of Natural History species account-Polar Bear
• USGS Polar Bear Studies

v • d • e Extant species of family Ursidae
Kingdom: Animalia · Phylum: Chordata · Class: Mammalia · Order: Carnivora · Suborder: Caniformia
Ailuropodinae	Ailuropoda Giant Panda (Ailuropoda melanoleuca)
Tremarctinae	Tremarctos Spectacled Bear (Tremarctos ornatus)
Ursinae	Ursus American Black Bear (Ursus americanus) · Asiatic Black Bear (Ursus thibetanus or Selenarctos thibetanus) · Brown Bear (Ursus arctos) · Polar bear (Ursus maritimus) Helarctos Sun Bear (Helarctos malayanus) Melursus Sloth Bear (Melursus ursinus)
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