Tuesday, November 6, 2012

Compared to the Antarctic

Compared to the Antarctic, where there is no major surface predator, Arctic seals use more breathing holes per individual, appear more restless when hauled out on the ice, and rarely defecate on the ice.[52] The baby fur of most Arctic seal species is white, presumably to provide camouflage from predators, whereas Antarctic seals all have dark fur at birth.[52] HP Compaq HSTNN-XB21 Battery

Polar bears rarely enter conflict with other predators, though recent brown bear encroachments into polar bear territories have led to antagonistic encounters. Brown bears tend to dominate polar bears in disputes over carcasses,[88] and dead polar bear cubs have been found in brown bear dens.[89] Wolves are rarely encountered by polar bears, though there are two records of wolf packs killing polar bear cubs.[90] HP Compaq HSTNN-XB24 Battery

Polar bears are sometimes the host of arctic mites such asAlaskozetes antarcticus.[52]

The Canadian Journal of Zoology tracked 52 sows in the southern Beaufort Sea off Alaska with GPS system collars; no boars were involved in the study due to males' necks being too thick for the GPS-equipped collars. Fifty long-distance swims were recorded; the longest at 354 kilometres (220 mi), with an average of 155 kilometres (96 mi). HP Compaq HSTNN-XB28 Battery

The length of these swims ranged from most of a day to ten days. Ten of the sows had a cub swim with them and after a year six cubs survived. The study did not determine if the others lost their cubs before, during, or some time after their long swims. Researchers do not know whether or not this is a new behavior; Before polar ice shrinkage, they opined that there was probably neither the need nor opportunity to swim such long distances. HP Compaq HSTNN-XB51 Battery

Polar bears have long provided important raw materials for Arctic peoples, including the Inuit, Yupik, Chukchi, Nenets, Russian Pomors and others. Hunters commonly used teams of dogs to distract the bear, allowing the hunter to spear the bear or shoot it with arrows at closer range.[92] Almost all parts of captured animals had a use.[93] HP Compaq HSTNN-XB52 Battery

The fur was used in particular to sew trousers 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 gallbladder and sometimes heart were dried and powdered for medicinal purposes; the large canine teeth were highly valued as talismans.[94] HP Compaq HSTNN-XB59 Battery

Only the liver was not used, as its high concentration of vitamin A is poisonous.[95] Hunters make sure to either toss the liver into the sea or bury it in order to spare their dogs from potential poisoning.[94] 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.[96] HP Compaq HSTNN-XB61 Battery

In Russia, polar bear furs were already being commercially traded in the 14th century, though it was of low value compared to Arctic Fox or even reindeer fur.[94] 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. HP Compaq HSTNN-XB62 Battery

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 Spitsbergen harvested 150 polar bears inMagdalenefjorden.[94] In the early 20th century, Norwegian hunters were harvesting 300 bears a year at the same location. HP Compaq HSTNN-XB68 Battery

Estimates of total historical harvest suggest that from the beginning of the 18th century, roughly 400 to 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.[94]

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.[98] HP Compaq HSTNN-XB69 Battery

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."[98] The numbers taken grew rapidly in the 1960s, peaking around 1968 with a global total of 1,250 bears that year.[99] HP Compaq HSTNN-XB85 Battery

Concerns over the future survival of the species led to the development of national regulations on polar bear hunting, beginning in the mid-1950s. The Soviet Union banned all hunting in 1956. Canada began imposing hunting quotas in 1968. Norway passed a series of increasingly strict regulations from 1965 to 1973, and has completely banned hunting since then. HP Compaq 500764-001 Battery

The United States began regulating hunting in 1971 and adopted the Marine Mammal Protection Act in 1972. In 1973, theInternational Agreement on the Conservation of Polar Bears was signed by all five nations whose territory is inhabited by polar bears: Canada, Denmark, Norway, the Soviet Union, and the United States. Member countries agreed to place restrictions on recreational and commercial hunting, ban hunting from aircraft and icebreakers, HP Compaq 500765-001 Battery

and conduct further research.[100] The treaty allows hunting "by local people using traditional methods". Norway is the only country of the five in which all harvest of polar bears is banned. The agreement was a rare case of international cooperation during the Cold War. BiologistIan 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. HP Compaq 501870-001 Battery

Such was the intensity of human fascination with this magnificent predator, the only marine bear."[101]

Agreements have been made between countries to co-manage their shared polar bear subpopulations. After several years of negotiations, Russia and the United States signed an agreement in October 2000 to jointly set quotas for indigenous subsistence hunting in Alaska and Chukotka.[102] The treaty was ratified in October 2007.[103] HP Compaq 513129-121 Battery

The Soviet Union banned the harvest of polar bears in 1956, however poaching continued and is believed to pose a serious threat to the polar bear population.[29]In recent years, polar bears have approached coastal villages in Chukotka more frequently due to the shrinking of the sea ice, endangering humans and raising concerns that illegal hunting would become even more prevalent.[104] HP Compaq 513129-141 Battery

In 2007, the Russian government made subsistence hunting legal for Chukotka natives only, a move supported by Russia's most prominent bear researchers and the World Wide Fund for Nature as a means to curb poaching.[104]

In Greenland, hunting restrictions were first introduced in 1994 and expanded by executive order in 2005.[29] Until 2005 Greenland placed no limit on hunting by indigenous people. HP Compaq 513129-421 Battery

However, in 2006 it imposed a limit of 150, while also allowed recreational hunting for the first time.[105] Other provisions included year-round protection of cubs and mothers, restrictions on weapons used, and various administrative requirements to catalogue kills.[29]

About 500 bears are killed per year by humans across Canada,[106] a rate believed by scientists to be unsustainable for some areas, notably Baffin Bay.[28] HP Compaq 532497-221 Battery

Canada has allowed sport hunters accompanied by local guides and dog-sled teams since 1970,[107] but the practice was not common until the 1980s.[108] The guiding of sport hunters provides meaningful employment and an important source of income for native communities in which economic opportunities are few.[31] Sport hunting can bring CDN$20,000 to $35,000 per bear into northern communities, which until recently has been mostly from American hunters. HP Compaq 532497-241 Battery

On 15 May 2008, the United States listed the polar bear as a threatened species under the Endangered Species Act and banned all importing of polar bear trophies. Importing products made from polar bears had been prohibited from 1972 to 1994 under the Marine Mammal Protection Act, and restricted between 1994 and 2008. Under those restrictions, HP Compaq 532497-421 Battery

permits from the United States Fish and Wildlife Service (FWS) were required to import sport-hunted polar bear trophies taken in hunting expeditions in Canada. The permit process required that the bear be taken from an area with quotas based on sound management principles.[110] Since 1994, more than 800 sport-hunted polar bear trophies have been imported into the U.S.[111] HP Compaq 572186-001 Battery

The territory of Nunavut accounts for the location 80% of annual kills in Canada.[106] In 2005, the government of Nunavut increased the quota from 400 to 518 bears,[109] despite protests from some scientific groups.[112] 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.[113] HP Compaq 572187-001 Battery

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)[108] Nunavut polar bear biologist, Mitchell Taylor, who was formerly responsible for polar bear conservation in the territory, insists that bear numbers are being sustained under current hunting limits. HP Compaq 572188-001 Battery

In 2010, the 2005 increase was partially reversed. Government of Nunavut officials announced that the polar bear quota for the Baffin Bay region would be gradually reduced from 105 per year to 65 by the year 2013.[115] The Government of the Northwest Territories maintain their own quota of 72 to 103 bears within the Inuvialuit communities of which some are set aside for sports hunters. HP Compaq 572189-001 Battery

Environment Canada also banned the export from Canada of fur, claws, skulls and other products from polar bears harvested in Baffin Bay as of 1 January 2010.[115]

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.[31] HP Compaq 572190-001 Battery

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. Whereas Native communities kill all the polar bears they are permitted to take each year, only half of sport hunters with permits actually manage to kill a polar bear. HP Compaq 572191-001 Battery

If a sport hunter does not kill a polar bear before his or her permit expires, the permit cannot be transferred to another hunter.

As of 2008, the World Conservation Union (IUCN) reports that the global population of polar bears is 20,000 to 25,000, and is declining.[1] HP Compaq 583256-001 Battery

In 2006, the IUCN upgraded the polar bear from a species of least concern to avulnerable species.[116] It cited a "suspected population reduction of >30% within three generations (45 years)", due primarily to climate change.[7] Other risks to the polar bear include pollution in the form of toxiccontaminants, conflicts with shipping, stresses from recreational polar-bear watching, and oil and gas exploration and development.[7] HP Compaq 586031-001 Battery

The IUCN also cited a "potential risk of over-harvest" through legal and illegal hunting.[7]

According to the World Wildlife Fund, the polar bear is important as an indicator of arctic ecosystem health. Polar bears are studied to gain understanding of what is happening throughout the Arctic, because at-risk polar bears are often a sign of something wrong with the arctic marine ecosystem.[117] HP Compaq 446398-001 Battery

The IUCN, 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 species.The key danger posed by climate change is malnutrition or starvation due to habitat loss. HP Compaq 446399-001 Battery

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.[83] Reduction in sea-ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning.[123] HP Compaq 451085-121 Battery

Thinner sea ice tends to deform more easily, which appears to make it more difficult for polar bears to access seals.[56] 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.

In addition to creating nutritional stress, a warming climate is expected to affect various other aspects of polar bear life: HP Compaq 451085-141 Battery

Changes in sea ice affect the ability of pregnant females to build suitable maternity dens. [24] As the distance increases between the pack ice and the coast, females must swim longer distances to reach favored denning areas on land.[27] Thawing of permafrost would affect the bears who traditionally den underground, and warm winters could result in den roofs collapsing or having reduced insulative value.[27] HP Compaq 451085-661 Battery

For the polar bears that currently den on multi-year ice, increased ice mobility may result in longer distances for mothers and young cubs to walk when they return to seal-hunting areas in the spring.[27]Disease-causing bacteria and parasites would flourish more readily in a warmer climate.[56]

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