Polar bear Totally Explained

Everything about The Polar Bear totally explained

The polar bear (Ursus maritimus) is a bear native to the Arctic Ocean and its surrounding seas. The world's largest predator found on land, an adult male weighs around 300–600 kg (660–1320 lb), while an adult female is about half that size. Although it's 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 the seals which make up most of its diet. As it can hunt consistently only from sea ice, the polar bear spends much of the year on the frozen sea, although most polar bears are born on land.
   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.
   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." 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). Likewise it's 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"). In Quebec, the polar bear is referred to as Ours polaire.
   The polar bear was previously considered to be in its own genus, Thalarctos. However, evidence of hybrids between polar bears and brown bears, and of the relatively recent evolutionary divergence of the two species, doesn't support the establishment of this separate genus, and the accepted scientific name is now therefore Ursus maritimus, as Phipps originally proposed.

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. meaning that the polar bear isn't a true species according to some species concepts. In addition, polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids, indicating that they've only recently diverged and are genetically similar. 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. 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. 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's 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.
   Modern methods of tracking polar bear populations have been implemented only since the mid-1980s, and are expensive to perform consistently over a large area. The Polar Bear Specialist Group of the IUCN takes the position that "estimates of subpopulation size or sustainable harvest levels shouldn't be made solely on the basis of traditional ecological knowledge without supporting scientific studies."
   Of the 19 recognized polar bear subpopulations, 5 are declining, 5 are stable, 2 are increasing, and 7 have insufficient data. 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 and the Arctic inter-island archipelagos. These areas have relatively high biological productivity in comparison to the deep waters of the high Arctic. 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.
   Annual ice contains areas of water that appear and disappear throughout the year as the weather changes. Seals migrate in response to these changes, and polar bears must follow their prey. 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. Adult males weigh 352–680 kg (775–1500+ lb) and measure 2.4–3.0 m (8–10 ft) in length. Adult females are roughly half the size of males and normally weigh 150–249 kg (330–550 lb), measuring 1.8–2.4 m (6–8 ft) in length. When pregnant, however, they can weigh as much as 499 kg (1,100 lb). The largest polar bear on record, reportedly weighing 1002 kg (2200 lb), was a male shot at Kotzebue Sound in northwestern Alaska in 1960. Compared with its closest relative, the brown bear, the polar bear has a more elongated body build and a longer skull and nose. The pads of the paws are covered with small, soft papillae which provide traction on the ice. there's no scientific evidence to support this claim.
   The 42 teeth of a polar bear reflect its highly carnivorous diet. Polar bears are superbly insulated by their 10 cm (4 in) of blubber, but, unlike other Arctic mammals, they don't 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. The white coat usually yellows with age. When kept in captivity in warm, humid conditions, it isn't unknown for the fur to turn a pale shade of green due to algae growing inside the guard hairs. 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. Its hearing is about as acute as that of a human, and its vision is also good at long distances.

Hunting and diet

Behavior

Unlike grizzly bears, polar bears are not territorial. Although stereotyped as being voraciously aggressive, they're normally cautious in confrontations, and often choose to escape rather than fight. Fat polar bears rarely attack humans unless severely provoked, whereas hungry polar bears are extremely unpredictable and are known to kill and sometimes eat humans. Polar bears are stealth hunters, and the victim is often unaware of the bear's presence until the attack is underway.
   In general, adult polar bears live solitary lives. Yet, they've often been seen playing together for hours at a time and even sleeping in an embrace,
   In 1992, a photographer near Churchill, Manitoba took a now widely-circulated set of photographs of a polar bear playing with a Canadian Eskimo dog a tenth of its size. The pair wrestled harmlessly together each afternoon for ten days in a row for no apparent reason, although the bear may have been trying to demonstrate its friendliness in the hope of sharing the kennel's food. This kind of social interaction is uncommon; it's far more typical for polar bears to behave aggressively towards dogs. 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.
   Between November and February, cubs are born blind, covered with a light down fur, and weighing less than 0.9 kg (2 lb). Males usually reach sexual maturity at six years, however as competition for females is fierce, many don't breed until the age of eight or ten. Polar bears rarely live beyond 25 years.

Ecological role

The polar bear is the apex predator within its range. Several animal species, particularly arctic foxes and glaucous gulls, routinely scavenge polar bear kills. 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. 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

Indigenous 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. Indeed, hunters make sure to either toss the liver into the sea or bury it in order to spare their dogs from potential poisoning. 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. 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. The numbers taken grew rapidly in the 1960s, peaking around 1968 with a global total of 1,250 bears that year.

Contemporary regulations

Concerns over the future survival of the species led to the development of national regulations on polar bear hunting, beginning in the mid-1950s. In 1973, the International Agreement on the Conservation of Polar Bears was signed by all five nations whose territory is inhabited by polar bears. Also known as the Oslo Agreement, it was a rare case of international cooperation during the Cold War. Biologist Ian Stirling commented, "For many years, the conservation of polar bears was the only subject in the entire Arctic that nations from both sides of the Iron Curtain could agree upon sufficiently to sign an agreement. Such was the intensity of human fascination with this magnificent predator, the only marine bear."
Although the agreement isn't enforceable in itself, member countries agreed to place restrictions on recreational and commercial hunting, ban hunting from aircraft and icebreakers, and conduct further research. The treaty allows hunting "by local people using traditional methods," although this has been liberally interpreted by member nations. Norway is the only country of the five in which all harvest of polar bears is banned.
Agreements have been made between countries to co-manage their shared polar bear subpopulations. After several years of negotiations, Russia and the U.S. signed an agreement in October 2000 to jointly set quotas for indigenous subsistence hunting in Alaska and Chukotka. The treaty was ratified in October 2007.

Russia

The Soviet Union banned all harvest of polar bears in 1956, however poaching continued and is believed to pose a serious threat to the polar bear population.

Greenland

In Greenland, restrictions for the species were first introduced in 1994 and expanded by executive order in 2005. Other provisions included year-round protection of cubs and mothers, restrictions on weapons used, and various administrative requirements to catalogue kills. a rate believed by scientists to be unsustainable for some areas, notably Baffin Bay. but the practice wasn't common until the 1980s.
   The 1972 United States Marine Mammal Protection Act prohibits the killing of polar bears and 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. Since 1994, more than 800 sport-hunted polar bear trophies have been imported into the U.S. 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.
   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. despite protests from some scientific groups. In two areas where harvest levels have been increased based on increased sightings, science-based studies have indicated declining populations, and a third area is considered data-deficient. 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. However, in 2006, the World Conservation Union (IUCN) upgraded the polar bear from a species of least concern to a vulnerable species It cited a "suspected population reduction of >30% within three generations (45 years)", due primarily to global warming.
   The key danger to polar bears is malnutrition or starvation due to global warming and 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've built sufficient fat reserves to survive the period of scarce food in the late summer and early fall. Reduction in sea-ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning.
   In Alaska, the effects of sea ice shrinkage have contributed to higher mortality rates in polar bear cubs, and have led to changes in the denning locations of pregnant females. 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.

Predictions

The U.S. 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. 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'd disappear from Greenland entirely and from the northern Canadian coast, leaving only dwindling numbers in the interior Arctic archipelago. 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." An additional risk to the species is that if individuals spend more time on land, that'll hybridize with brown or grizzly bears.
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.

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. Some estimates of the global population are around 5,000–10,000 in the early 1970s; other estimates were 20,000–40,000 during the 1980s. Current estimates put the global population at between 20,000 and 25,000. Second, controls of harvesting were introduced that allowed this previously-overhunted species to recover.
   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. 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.
   Debate over the listing has been unusual in that it has put conservation groups and Canada's Inuit at opposing positions; Many Inuit believe the polar bear population is increasing, and it's likely that a listing under the Endangered Species Act would lead to restrictions on sport-hunting and therefore a loss of income to their communities.
   On May 14, 2008 the Bush Administration listed the polar bear under the Endangered Species Act. The Administration listed the polar bear as threatened instead of endangered, and invoked a clause (known as a "4(d) exemption") that excludes global warming from the list of threats the federal government has to consider when trying to protect polar bear habitat.

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. and 1500 year old cave paintings of polar bears have been found in Chukotka. Only once the spirit was appeased, would the skull be separated from the skin, taken beyond the bounds of the homestead, and placed in the ground, facing North. 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. 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.

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