Emergency Preparedness for Disabilities & Special Needs Groups

 Polar Bear

The polar bear (Ursus maritimus) is a bear native to the Arctic. It is the world's largest land carnivore, with most adult males weighing 300-600 kg (660-1320 lb); adult females are about half the size of males. Its fur is hollow and translucent, but usually appears as white or cream coloured, thus providing the animal with effective camouflage. Its skin is actually black in color.[2] Its thick blubber and fur insulate it against the cold. The bear has a short tail and small ears that help reduce heat loss, as well as a relatively small head and long, tapered body to streamline it for swimming.
A semi-aquatic marine mammal, the polar bear has adapted for life on a combination of land, sea, and ice, [3] and is the apex predator within its range. It feeds mainly on seals, young walruses, and whales, although it will eat anything it can kill. It is the bear species most likely to prey on humans.
The polar bear is a vulnerable species. Some scientists and climatologists believe that the projected decreases in the polar sea ice due to global warming will have a significant negative impact on of this species within this century.[1],[4] No global census exists, but local long-term studies show population declines of some groups of bears.[5][6] The Center for Biological Diversity petitioned to up-list polar bears as a threatened species in 2005.[7] This petition and the data behind it have been disputed by two professionals.[8],[9]
Contents

1 Physical description
1.1 Size and weight
1.2 Fur and skin
2 Evolution
2.1 Speciation
2.2 Subspecies and populations
3 Natural range
4 Hunting, diet and feeding
5 Breeding
6 Conservation status
7 Threats natural and unnatural
8 Entertainment and commerce
9 Gallery
10 See also
11 References
12 External links


Physical description

Size and weight
Polar bears rank with the Kodiak bear as among the largest living land carnivores, and male polar bears may weigh twice as much as a Siberian tiger. Most adult males weigh 300–600 kg (660–1320 lb) and measure 2.4–3.0 m (7.9–10.0 ft) in length. When standing upright, an adult male can stand up to 3.35 m (11.5 ft). That is about as tall as an elephant. Adult females are roughly half the size of males and normally weigh 150–300 kg (330–660 lb), measuring 1.9–2.1 m (6.25–7 ft).[10][11] The great difference in body size makes the polar bear the second most sexually dimorphic of mammals, following the eared seals [12]. At birth, cubs weigh only 600–700 g or about a pound and a half. The largest polar bear on record was a huge male, allegedly weighing 1002 kg (2200 lb) shot at Kotzebue Sound in northwestern Alaska in 1960.[13]
[edit] Fur and skin
 
A Polar Bear resting.
A polar bear's fur is white (individual hairs are transparent, like the water droplets that make up a cloud) and provides good camouflage and insulation. It may yellow with age. Stiff hairs on the pads of its paws provide insulation and traction on ice.
Polar bears gradually molt their hair from May to August[14]; however, unlike other Arctic mammals, polar bears do not shed their coat for a darker shade to camouflage themselves in the summer habitat. It was once conjectured that the hollow guard hairs of a polar bear coat acted as fiber-optic tubes to conduct light to its black skin, where it could be absorbed - a theory disproved by recent studies.[15] The thick undercoat does, however, insulate the bears: they overheat at temperatures above 10 °C (50 °F), and are nearly invisible under infrared photography; only their breath and muzzles can be easily seen.[16] When kept in captivity in warm, humid conditions, it is not unknown for the fur to turn a pale shade of green. This is due to algae growing inside the guard hairs - in unusually warm conditions, the hollow tubes provide an excellent home for algae. Whilst 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 peroxide bleach to make the fur white again.
The guard hair is 5-15 cm over of most the body of polar bears. [17] However, in the forelegs, males have significantly longer, increasing in length until 14 years of age. The ornamental foreleg hair is suggested as a form of an attractive trait for females, likened to the lion mane.[12]
Evolution
Speciation
The raccoon and bear families are believed to have diverged about 30 million years ago. The spectacled bear split from other bears around 13 million years ago. The six distinct ursine species originated some 4 million years ago. According to both fossil and DNA evidence, the polar bear diverged from the brown bear roughly 200 thousand years ago; 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 have, however, bred with brown bears to produce fertile grizzly–polar bear hybrids,[18] [19] suggesting that the two are close relatives. But neither species can survive long in the other's niche, and with distinctly different morphology, metabolism, social and feeding behaviors, and other phenotypic characters, the two bears are generally classified as separate species.
In a widely cited paper published in 1996, a comparison of the DNA of various brown bear populations showed that the brown bears of Alaska's ABC islands shared a more recent common ancestor with polar bears than with any other brown bear population in the world.[20] Also to see how the bear species once split yet are still connected, polar bears still have HIT (hibernation induction trigger) in their blood, but they also utilize this to hibernate as the brown bear does. They may occasionally enter a dormant state referred to as "denning" (pregnant females in particular), though their body temperature does not decrease during this period as it would for a typical mammal in hibernation.[21]
Subspecies and populations
Many sources list no polar bear subspecies,[22] while others list two - Ursus maritimus maritimus and Ursus maritimus marinus.[23][24] The number of populations varies depending upon who is counting. The IUCN/SSC Polar Bear Specialist Group (PBSG), the pre-eminent international scientific body for research and management of polar bears, recognizes twenty populations, or stocks, worldwide.[16] Other scientists recognize six distinct populations.[25]
Canadian Arctic archipelago
Greenland
Spitzbergen-Franz Josef Land
Central Siberia
[edit] Natural range
 
A Polar Bear in Churchill, Manitoba
 
Three Polar Bears investigate the submarine USS Honolulu 280 miles (450 km) from the North Pole.
 
Mother and two cubs climbing up Guillemot Island, Ukkusiksalik National Park.
Though it spends time on land and ice, the polar bear is regarded as a marine mammal due to its intimate relationship with the sea.[26] The circumpolar species is found in and around the Arctic Ocean, its southern range limited by pack ice. Their southernmost point is James Bay in Canada. While their numbers thin north of 88 degrees, there is evidence of polar bears all the way across the Arctic. Population is estimated to be between 20,000 to 25,000.[27]
The main population centers are:
Wrangell Island and western Alaska
Northern Alaska
Canadian Arctic archipelago
Greenland
Svalbard-Franz Josef Land
North-Central Siberia
Their range is limited by the availability of that sea ice they use as a platform for hunting seals, the mainstay of their diet. The destruction of its habitat on the Arctic ice threatens the bear's survival as a species. [28] [29]
Hunting, diet and feeding
The polar bear is the most carnivorous member of the bear family, and the one that is most likely to prey on humans as food. It feeds mainly on seals, especially ringed seals that poke holes in the ice to breathe, but will eat anything it can kill: birds, rodents, shellfish, crabs, beluga whales, young walruses, occasionally muskox or reindeer, and very occasionally other polar bears. Still, reindeer and musk oxen can easily outrun a polar bear, and polar bears overheat quickly: thus the polar bear subsists almost entirely on live seals and walrus calves, or on the carcasses of dead adult walruses or whales. They are enormously powerful predators, but they rarely kill adult walruses, which are twice the polar bear's weight, although such an adult walrus kill has been recored on tape.[1] Humans are the only predators of polar bears. As a carnivore which feeds largely upon fish-eating carnivores, the polar bear ingests large amounts of vitamin A, which is stored in their livers; in the past, humans have been poisoned by eating the livers of polar bears.[30] Though mostly carnivorous, they sometimes eat berries, roots, and kelp in the late summer.
 
Polar bear diving in a zoo.
Polar bears are excellent swimmers and have been seen in open Arctic waters as far as 60 miles (100 km) from land. In some cases they spend half their time on ice floes. Their 12 cm (5 in) layer of fat adds buoyancy in addition to insulating them from the cold. 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.[31]
Polar bears are enormous, aggressive, curious, and potentially dangerous to humans. Wild polar bears, unlike most other bears, are barely habituated to people and will quickly size up any animal they encounter as potential prey.
Like other bear species, they have developed a liking for garbage as a result of human encroachment. For example, the dump in Churchill, Manitoba was frequently scavenged by polar bears, who have been observed eating, among other things, grease and motor oil. [32]. To protect the bears, the dump was closed in 2006. Garbage is now recycled or transported to Thompson, Manitoba.[33]
Breeding
The 2004 National Geographic study found no cases of cubs being born as triplets, a common event in the 1970s, and that only one in twenty cubs were weaned at eighteen months, as opposed to half of cubs three decades earlier.[29]
In Alaska, the United States Geological Survey reports that 42 percent of cubs now reach 12 months of age, down from 65 percent 15 years ago.[34] In other words, less than two of every three cubs that survived 15 years ago are now making it past their first year.
The USGS has also published research which purports that the percentage of Alaskan polar bears that den on sea ice has changed from 62% between the years 1985-1994, to 37% over the years 1998-2004. The Alaskan population thus now more resembles the world population, in that it is more likely to den on land.[35]
Conservation status
The World Conservation Union listed polar bears as a vulnerable species, one of three sub-categories of threatened status, in May 2006.[36]
Although no global census exists, 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.[6],[7] In the Western Hudson Bay in Canada, for example, there were an estimated 1200 polar bears in 1987, and 950 in 2007.[37] In the absence of global data, the need for species protection has been disputed by two professionals: H. Sterling Burnett and Mitchell K. Taylor. Burnett, a senior fellow for the National Center for Policy Analysis have claimed that the total global population of polar bears increased from 5,000 to 25,000 between the 1970s and 2007.[9] Between 1965 and 1970 the population of polar bears was estimated at only 8,000 - 10,000 and it was classified as an endangered species. This increase coincides with changes in hunting practices which began in the early 1970s. For example, the USA adopted the Marine Mammal Protection Act in 1972, and in 1973 the International Agreement for the Conservation of Polar Bears was signed by Canada, Denmark, Norway, the USSR and the USA.[38] Mitch Taylor, the Nunavut Government Manager of Wildlife Research, wrote a letter to the US Fish and Wildlife Service arguing that local studies are insufficient evidence for global protection at this time.[8] These claims have received much attention from the media.[39],[40],[41]
In February 2005 the environmental group, Center for Biological Diversity, with support from American senator Joe Lieberman, petitioned the United States Fish and Wildlife Service (FWS), part of the Department of the Interior to use the Endangered Species Act and list the bears as a threatened species. [7],[42]
Under United States law the FWS was required to respond to the petition within 90 days, [42] but in October 2005 after no reply had been received the Center for Biological Diversity threatened to sue the United States Government. On 14 December 2006 the Center for Biological Diversity along with Greenpeace and the Natural Resources Defense Council filed a lawsuit in California. [43]
On December 27, 2006, the United States Department of the Interior in agreement with the three groups proposed that polar bears be added to the endangered species list, the first change of this type to be attributed to global warming. It will take up to a year to make the final determination. [44] The Natural Resources Defense Council contends that though it is "a big step forward" the proposal fails to identify global warming pollution as the cause of rising Arctic temperatures and vanishing sea ice. In addition, it says the proposal offered by Dr. Rosa Meehan, Supervisor of the U.S. Fish and Wildlife Service, does not designate any of the land discussed as the kind of habitat that is essential for the polar bear's survival as "critical habitat" that could help the bear recover. [45][46]
On September 7, 2007 the United States Geological Survey estimated that two-thirds of the world's polar bears will disappear by 2050, even under moderate projections for the shrinking of summer sea ice caused by greenhouse gasses in the atmosphere. The current bear population is estimated at 22,000. [47]
Threats natural and unnatural
 
Tourists watching Polar Bears from a "tundra buggy" near Churchill, Manitoba.
The most immediate and topically recognized threats to the polar bear are the drastic changes taking place in their natural habitat, which is literally melting away due to global warming.[48][49]The United States Geological Survey, for example, in November 2006, stated that the loss of sea ice in the Alaskan portion of the Beaufort Sea has led to a higher death rate for polar bear cubs.[50]


A 1999 study of polar bears on Hudson Bay showed that rising temperatures are thinning the pack ice from which the bears hunt, driving them to shore weeks before they've caught enough food to get them through hibernation[51] and leading to a 21% decline in the local population. [9]
The BBC reported:
Climate change is threatening polar bears with starvation by shortening their hunting season, according to a study by scientists from the Canadian Wildlife Service.[52]
There is also some concern over pollution in addition to the normal natural problems the bears might face.[53] Reduced cub survival has been reported in connection with PCBs, as well as reports of organochlorines affecting the endocrine system and immune systems with lower immunoglobulin G seen with increasing PCB levels.[54][55] The lipophilic PCBs are considered a serious threat to marine mammals generally and to their food web, quickly concentrating into fat and blubber. These and related compounds are known in mammals (including humans) to cause such things as abortion, still births, alteration of the menstrual cycle, poor growth and survival of young, carcinogenicity, immunotoxicity, and even outright lethality. Other classes of organohalogens have been found in polar bears, such as PCDDs, PCDFs, TCPMe and TCPMeOH. Hermaphroditic polar bears[2] have now been observed in less pristine areas. While some countries now ban some of these substances, they are still produced in others, and still end up all over the entire planet including the formerly pristine arctic. Even after the use of these chemicals is stopped, they continue to accumulate up the food chain, including in marine mammals and humans, for some time to come.
The bears sometimes have problems with various skin diseases with dermatitis caused sometimes by mites or other parasites. The bears are especially susceptible to Trichinella, a parasitic roundworm they contract by eating infected seals.[56] 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. Interestingly, 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 it encounters, and in such a challenging habitat even minor weaknesses can lead to serious problems and quick death.
Entertainment and commerce

Polar bears have been made both controversial and famous for their distinctive white fur and their habitat. Companies like Coca-Cola, Polar Beverages, Nelvana, Bundaberg Rum and Good Humor-Breyers have used images of this bear in logos. The first has consistently displayed the bears as thriving near penguins, though the animals naturally live in opposite hemispheres. The Canadian 2-dollar coin (right) features the image of a polar bear. The panserbjørne of the fantasy trilogy His Dark Materials are polar bears with human-level intelligence. The TV series Lost has featured polar bears on a mysterious tropical island where they are portrayed as fearsome beasts. Also, a polar bear was chosen as mascot for the 1988 Winter Olympics held in Calgary, Canada. The Polar Bear is the mascot of Bowdoin college. The Northwest Territories of Canada have a licence plate in the shape of a polar bear.