Polar Bear

Polar Bear

Overview
The polar bear is a bear
Bear
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

 native largely within the Arctic Circle
Arctic Circle
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. For Epoch 2011, it is the parallel of latitude that runs north of the Equator....

 encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest land carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

 and also the largest bear, together with the omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...

 Kodiak Bear
Kodiak Bear
The Kodiak bear , also known as the Kodiak brown bear or the Alaskan grizzly bear or American brown bear, occupies the islands of the Kodiak Archipelago in South-Western Alaska. Its name in the Alutiiq language is Taquka-aq. It is the largest subspecies of brown bear.- Taxonomy :Taxonomist C.H...

, which is approximately the same size. An adult male weighs around 350 kilogram, while an adult female is about half that size. Although it is closely related to the brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

, it has evolved to occupy a narrower ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

 which make up most of its diet.
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Encyclopedia
The polar bear is a bear
Bear
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

 native largely within the Arctic Circle
Arctic Circle
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. For Epoch 2011, it is the parallel of latitude that runs north of the Equator....

 encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest land carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

 and also the largest bear, together with the omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...

 Kodiak Bear
Kodiak Bear
The Kodiak bear , also known as the Kodiak brown bear or the Alaskan grizzly bear or American brown bear, occupies the islands of the Kodiak Archipelago in South-Western Alaska. Its name in the Alutiiq language is Taquka-aq. It is the largest subspecies of brown bear.- Taxonomy :Taxonomist C.H...

, which is approximately the same size. An adult male weighs around 350 kilogram, while an adult female is about half that size. Although it is closely related to the brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

, it has evolved to occupy a narrower ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

 which make up most of its diet. Although most polar bears are born on land, they spend most of their time at sea. Their scientific name means "maritime
Sea
A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

 bear", and derives from this fact. Polar bears can hunt their preferred food of seals from the edge of sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....

, often living off fat reserves when no sea ice is present.

The polar bear is classified as a vulnerable species
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...

, with eight of the nineteen polar bear subpopulations in decline. For decades, large scale hunting raised international concern for the future of the species but populations rebounded after controls and quotas began to take effect. For thousands of years, the polar bear has been a key figure in the material, spiritual, and cultural life of Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 indigenous peoples
Indigenous peoples
Indigenous peoples are ethnic groups that are defined as indigenous according to one of the various definitions of the term, there is no universally accepted definition but most of which carry connotations of being the "original inhabitants" of a territory....

, and polar bears remain important in their cultures.

Naming and etymology


Constantine John Phipps
Constantine Phipps, 2nd Baron Mulgrave
Constantine John Phipps, 2nd Baron Mulgrave, PC was an English explorer and officer in the Royal Navy. He served during the Seven Years War and the American War of Independence, seeing action in a number of battles and engagements...

 was the first to describe the polar bear as a distinct species in 1774. He chose the scientific name Ursus maritimus, the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for 'maritime bear', due to the animal's native habitat. The Inuit
Inuit
The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 refer to the animal as nanook
Nanook
In Inuit mythology, Nanook or Nanuq , which is from the Inuit language for polar bear, was the master of bears, meaning he decided if hunters had followed all applicable taboos and if they deserved success in hunting bears....

(transliterated
Transliteration
Transliteration is a subset of the science of hermeneutics. It is a form of translation, and is the practice of converting a text from one script into another...

 as nanuq in the Inupiat language
Inupiat language
The Inupiat language, also known as Inupiatun, Inupiaq, Iñupiaq, Inyupiaq, Inyupiat, Inyupeat, Inyupik, and Inupik, is a group of dialects of the Inuit language, spoken in northern and northwestern Alaska. The Iñupiaq language is a member of the Eskimo languages group. There are roughly 2,100...

). The Yupik also refer to the bear as nanuuk in Siberian Yupik
Siberian Yupik language
Siberian Yupik is one of the four Yupik languages:* Central Siberian Yupik,...

. The bear is umka in the Chukchi language
Chukchi language
The Chukchi language is a Palaeosiberian language spoken by Chukchi people in the easternmost extremity of Siberia, mainly in Chukotka Autonomous Okrug...

. In Russian, it is usually called бе́лый медве́дь (bélyj medvédj, the white bear), though an older word still in use is ошку́й (Oshkúj, which comes from the Komi
Komi language
The Komi language is a Finno-Permic language spoken by the Komi peoples in the northeastern European part of Russia. Komi is one of the two members of the Permic subgroup of the Finno-Ugric branch...

 oski, "bear"). In French, the polar bear is referred to as ours blanc ("white bear") or ours polaire ("polar bear"). In the Norwegian-administered Svalbard
Svalbard
Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands range from 74° to 81° north latitude , and from 10° to 35° east longitude. Spitsbergen is the...

 archipelago, the polar bear is referred to as Isbjørn ("ice bear").

The polar bear was previously considered to be in its own genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, Thalarctos. However, evidence of hybrids between polar bears and brown bears
Ursid hybrid
An ursid hybrid is an animal with parents from two different species or subspecies of the Ursidae family. Species and subspecies of bear known to have produced offspring with another bear species or subspecies include brown bears, black bears, grizzly bears and polar bears, all of which are...

, and of the 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.

Taxonomy and evolution



The bear family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

, 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 150,000 years ago. The oldest known polar bear fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 is a 130,000 to 110,000-year-old jaw bone, found on Prince Charles Foreland
Prince Charles Foreland
Prince Charles Foreland, , is an island in the Arctic archipelago Svalbard. The island is directly west of Oscar II Land on Spitsbergen and constitutes the western part of Svalbard...

 in 2004. Fossils show that between ten to twenty thousand years ago, the polar bear's molar teeth
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

 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
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

.

More recent genetic studies have shown that some clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s of brown bear are more closely related to polar bears than to other brown bears, meaning that the polar bear is not a true species according to some species concepts. Irish brown bears are particularly close to polar bears. In addition, polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids, indicating that they have only recently diverged and are genetically similar. However, because neither species can survive long in the other's ecological niche, and because they have different morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

, metabolism, social and feeding behaviors, and other phenotypic
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...

 characteristics, the two bears are generally classified as separate species.

The evolution of the polar bear from the brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

 is an example of peripatric speciation
Peripatric speciation
Peripatric and peripatry are terms from biogeography, referring to organisms whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur – for example a wide river or a mountain range. Such organisms are usually closely related Peripatric and...

, the process by which an ancestral species gives rise to a daughter species through the evolution of populations located at the margin of the ancestral species' range. The origin of the polar bear therefore rendered the ancestral brown bear a paraspecies
Paraspecies
A paraspecies is a species, living or fossil, that gave rise to one or more daughter species without itself becoming extinct. The concept of a paraspecies emerges naturally from the Evolutionary Species Concept . Geographically widespread species that have given rise to one or more daughter...

, which is paraphyletic species that gave rise to one or more daughter species without itself becoming extinct.

When the polar bear was originally documented, two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 were identified: Ursus maritimus maritimus by Constantine J. Phipps in 1774, and Ursus maritimus marinus by Peter Simon Pallas
Peter Simon Pallas
Peter Simon Pallas was a German zoologist and botanist who worked in Russia.- Life and work :Pallas was born in Berlin, the son of Professor of Surgery Simon Pallas. He studied with private tutors and took an interest in natural history, later attending the University of Halle and the University...

 in 1776. This distinction has since been invalidated.

One fossil subspecies has been identified. Ursus maritimus tyrannus
Ursus maritimus tyrannus
Ursus maritimus tyrannus was a very large fossil subspecies of polar bear, descended from an Arctic population of brown bears. Its name in Latin means tyrant sea bear. The species is mentioned by Björn Kurtén, who assigned it to a Polar bear subspecies, U. m. tyrannus. Its bones have been found in...

—descended from Ursus arctos—became extinct during the Pleistocene. U.m. tyrannus was significantly larger than the living subspecies.

Population and distribution



The polar bear is found in the Arctic Circle and adjacent land masses as far south as Newfoundland Island. Due to the absence of human development in its remote habitat, it retains more of its original range than any other extant carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

. 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
James Bay
James Bay is a large body of water on the southern end of Hudson Bay in Canada. Both bodies of water extend from the Arctic Ocean. James Bay borders the provinces of Quebec and Ontario; islands within the bay are part of Nunavut...

 in Canada. They can occasionally drift
Drift ice
Drift ice is ice that floats on the surface of the water in cold regions, as opposed to fast ice, which is attached to a shore. Usually drift ice is carried along by winds and sea currents, hence its name, "drift ice"....

 widely with the sea ice, and there have been anecdotal sightings as far south as Berlevåg
Berlevåg
is a municipality in Finnmark county, Norway. The administrative centre of the municipality is the village of Berlevåg. Berlevåg was separated from the municipality of Tana to form a municipality of its own on 1 July 1913....

 on the Norwegian mainland and the Kuril Islands
Kuril Islands
The Kuril Islands , in Russia's Sakhalin Oblast region, form a volcanic archipelago that stretches approximately northeast from Hokkaidō, Japan, to Kamchatka, Russia, separating the Sea of Okhotsk from the North Pacific Ocean. There are 56 islands and many more minor rocks. It consists of Greater...

 in the Sea of Okhotsk
Sea of Okhotsk
The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, lying between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaidō to the far south, the island of Sakhalin along the west, and a long stretch of eastern Siberian coast along the west and...

. It is difficult to estimate a global population of polar bears as much of the range has been poorly studied; however, biologists use a working estimate of about 20,000–25,000 polar bears worldwide.

There are 19 generally recognized, discrete subpopulations. The subpopulations display seasonal fidelity to particular areas, but DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 studies show that they are not reproductively isolated. The thirteen North American subpopulations range from the Beaufort Sea
Beaufort Sea
The Beaufort Sea is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, west of Canada's Arctic islands. The sea is named after hydrographer Sir Francis Beaufort...

 south to Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...

 and east to Baffin Bay
Baffin Bay
Baffin Bay , located between Baffin Island and the southwest coast of Greenland, is a marginal sea of the North Atlantic Ocean. It is connected to the Atlantic via Davis Strait and the Labrador Sea...

 in western Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

 and account for about 70% of the global population. The Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

n population is broken up into the eastern Greenland, Barents Sea
Barents Sea
The Barents Sea is a marginal sea of the Arctic Ocean, located north of Norway and Russia. Known in the Middle Ages as the Murman Sea, the sea takes its current name from the Dutch navigator Willem Barents...

, Kara Sea
Kara Sea
The Kara Sea is part of the Arctic Ocean north of Siberia. It is separated from the Barents Sea to the west by the Kara Strait and Novaya Zemlya, and the Laptev Sea to the east by the Severnaya Zemlya....

, Laptev Sea
Laptev Sea
The Laptev Sea is a marginal sea of the Arctic Ocean. It is located between the northern coast of Siberia, the Taimyr Peninsula, Severnaya Zemlya and the New Siberian Islands. Its northern boundary passes from the Arctic Cape to a point with co-ordinates of 79°N and 139°E, and ends at the Anisiy...

, and Chukchi Sea
Chukchi Sea
Chukchi Sea is a marginal sea of the Arctic Ocean. It is bounded on the west by the De Long Strait, off Wrangel Island, and in the east by Point Barrow, Alaska, beyond which lies the Beaufort Sea. The Bering Strait forms its southernmost limit and connects it to the Bering Sea and the Pacific...

 subpopulations, though there is considerable uncertainty about the structure of these populations due to limited mark and recapture
Mark and recapture
Mark and recapture is a method commonly used in ecology to estimate population size. This method is most valuable when a researcher fails to detect all individuals present within a population of interest every time that researcher visits the study area...

 data.
The range includes the territory of five nations: Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 (Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

), Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 (Svalbard
Svalbard
Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands range from 74° to 81° north latitude , and from 10° to 35° east longitude. Spitsbergen is the...

), Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 (Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

) and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. These five nations are the signatories of the International Agreement on the Conservation of Polar Bears
International Agreement on the Conservation of Polar Bears
The International Agreement on the Conservation of Polar Bears was signed in Oslo, November 15, 1973 by the five nations with the largest polar bear populations including Canada, Denmark, Greenland, Norway, the United States, and the former U.S.S.R...

, 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 most accurate counts require flying a helicopter in the Arctic climate
Climate of the Arctic
The climate of the Arctic is characterized by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter...

 to find polar bears, shooting a tranquilizer dart at the bear to sedate it, and then tagging the bear. In Nunavut
Nunavut
Nunavut is the largest and newest federal territory of Canada; it was separated officially from the Northwest Territories on April 1, 1999, via the Nunavut Act and the Nunavut Land Claims Agreement Act, though the actual boundaries had been established in 1993...

, some Inuit have reported increases in bear sightings around human settlements in recent years, leading to a belief that populations are increasing. 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. The Polar Bear Specialist Group of the IUCN takes the position that "estimates of subpopulation size or sustainable harvest
Sustainable yield
The sustainable yield of natural capital is the ecological yield that can be extracted without reducing the base of capital itself, i.e. the surplus required to maintain ecosystem services at the same or increasing level over time. This yield usually varies over time with the needs of the...

 levels should not be made solely on the basis of traditional ecological knowledge without supporting scientific studies."

Of the 19 recognized polar bear subpopulations, eight are declining, three are stable, one is increasing, and seven have insufficient data, as of 2009.

Habitat



The polar bear is often regarded as a marine mammal
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...

 because it spends many months of the year at sea. Its preferred habitat is the annual sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....

 covering the waters over the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...

 and the Arctic inter-island archipelago
Archipelago
An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...

s. These areas, known as the "Arctic ring of life", have high biological productivity in comparison to the deep waters of the high Arctic. The polar bear tends to frequent areas where sea ice meets water, such as polynya
Polynya
A polynya or polynia is an area of open water surrounded by sea ice. It is now used as geographical term for an area of unfrozen sea within the ice pack. It is a loanword from , , which means a natural ice hole, and was adopted in the 19th century by polar explorers to describe navigable...

s and leads (temporary stretches of open water in Arctic ice), to hunt the seals that make up most of its diet. Polar bears are therefore found primarily along the perimeter of the polar ice pack
Polar ice packs
Polar ice packs are large areas of pack ice formed from seawater in the Earth's polar regions, known as polar ice caps: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the Antarctic ice sheet. Polar packs significantly change their size during...

, rather than in the Polar Basin
North Polar Basin
The North Polar Basin is an oceanic basin in the Arctic Ocean, consisting of two main parts, the Amerasian Basin and the Eurasian Basin , which are separated by the Lomonosov Ridge, a mid-ocean ridge running between north Greenland and the New Siberian Islands...

 close to the North Pole
North Pole
The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets its surface...

 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
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...

, James Bay
James Bay
James Bay is a large body of water on the southern end of Hudson Bay in Canada. Both bodies of water extend from the Arctic Ocean. James Bay borders the provinces of Quebec and Ontario; islands within the bay are part of Nunavut...

, 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. In the Chukchi
Chukchi Sea
Chukchi Sea is a marginal sea of the Arctic Ocean. It is bounded on the west by the De Long Strait, off Wrangel Island, and in the east by Point Barrow, Alaska, beyond which lies the Beaufort Sea. The Bering Strait forms its southernmost limit and connects it to the Bering Sea and the Pacific...

 and Beaufort
Beaufort Sea
The Beaufort Sea is a marginal sea of the Arctic Ocean, located north of the Northwest Territories, the Yukon, and Alaska, west of Canada's Arctic islands. The sea is named after hydrographer Sir Francis Beaufort...

 seas, polar bears retreat each summer to the ice further north that remains frozen year-round.

Physical characteristics



The polar bear is the largest terrestrial carnivore, being more than twice as big as the Siberian tiger. It shares this title with the Kodiak Bear
Kodiak Bear
The Kodiak bear , also known as the Kodiak brown bear or the Alaskan grizzly bear or American brown bear, occupies the islands of the Kodiak Archipelago in South-Western Alaska. Its name in the Alutiiq language is Taquka-aq. It is the largest subspecies of brown bear.- Taxonomy :Taxonomist C.H...

. Adult males weigh 350–680 kg (770–1500 lbs) and measure 2.4–3 m (7.9–9.8 ft) in length. Adult females are roughly half the size of males and normally weigh 150 kilogram, measuring 1.8–2.4 m (5.9–7.9 ft) in length. When pregnant, however, they can weigh as much as 499 kg (1,100.1 lb). The polar bear is among the most sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

 of mammals, surpassed only by the pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...

s. The largest polar bear on record, reportedly weighing 1002 kg (2,209 lb), was a male shot at Kotzebue Sound
Kotzebue Sound
Kotzebue Sound is an arm of the Chukchi Sea in the western region of the U.S. state of Alaska. It is on the north side of the Seward Peninsula and bounded the east by the Baldwin Peninsula. It is long and wide....

 in northwestern Alaska in 1960. The shoulder height of the polar bear is 130–160 cm (51–63 in).

Compared with its closest relative, the brown bear, the polar bear has a more elongated body build and a longer skull and nose. As predicted by Allen's rule
Allen's rule
Allen's rule is a biological rule posited by Joel Asaph Allen in 1877. It states that endotherms from colder climates usually have shorter limbs than the equivalent animals from warmer climates.- Theory :...

 for a northerly animal, the legs are stocky and the ears and tail are small. However, the feet are very large to distribute load when walking on snow or thin ice and to provide propulsion when swimming; they may measure 30 cm (12 in) across in an adult. The pads of the paws are covered with small, soft papillae (dermal bumps) which provide traction on the ice. The polar bear's claws are short and stocky compared to those of the brown bear, perhaps to serve the former's need to grip heavy prey and ice. The claws are deeply scooped on the underside to assist in digging in the ice of the natural habitat. Despite a recurring Internet meme
Internet meme
The term Internet meme is used to describe a concept that spreads via the Internet. The term is a reference to the concept of memes, although the latter concept refers to a much broader category of cultural information.-Description:...

 that all polar bears are left-handed, there is no scientific evidence to support this claim. Unlike the brown bear, polar bears in captivity are rarely overweight or particularly large, possibly as a reaction to the warm conditions of most zoos.

The 42 teeth of a polar bear reflect its highly carnivorous diet. The cheek teeth are smaller and more jagged than in the brown bear, and the canines
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

 are larger and sharper. The dental formula is
Polar bears are superbly insulated by up to 10 cm (3.9 in) of blubber
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...

, their hide and their fur; they overheat at temperatures above 10 °C (50 °F), and are nearly invisible under infrared photography
Infrared photography
In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about...

. Polar bear fur consists of a layer of dense underfur and an outer layer of guard hair
Guard hair
Guard hairs are the longest, coarsest hairs in a mammal's coat, forming the topcoat . They taper to a point and protect the undercoat from the elements. They are often water repellent and stick out above the rest of the coat...

s, which appear white to tan but are actually transparent. The guard hair is 5 centimetre over most of the body. Polar bears gradually moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...

 from May to August, 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.

The white coat usually yellows with age. When kept in captivity in warm, humid conditions, the fur may turn a pale shade of green due to algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 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.

The polar bear has an extremely well developed sense of smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...

, being able to detect seals nearly 1 mi (1.6 km) away and buried under 3 ft (0.9144 m) of snow. Its hearing is about as acute as that of a human, and its vision is also good at long distances.

The polar bear is an excellent swimmer
Aquatic locomotion
Swimming is biologically propelled motion through a liquid medium. Swimming has evolved a number of times in a range of organisms ranging from arthropods to fish to molluscs.-Evolution of swimming:...

 and individuals have been seen in open Arctic waters as far as 200 mi (321.9 km) from land. With its body fat providing buoyancy, it swims in a dog paddle fashion using its large forepaws for propulsion. Polar bears can swim 6 mph (2.7 m/s). When walking, the polar bear tends to have a lumbering gait and maintains an average speed of around 3.5 mph (1.6 m/s). When sprinting, they can reach up to 25 mph (11.2 m/s).

Hunting and diet



The polar bear is the most carnivorous member of the bear family, and most of its diet consists of ringed
Ringed Seal
The ringed seal , also known as the jar seal and as netsik or nattiq by the Inuit, is an earless seal inhabiting the Arctic and sub-Arctic regions...

 and bearded seal
Bearded Seal
The bearded seal , also called the square flipper seal, is a medium-sized pinniped that is found in and near to the Arctic Ocean. It gets its generic name from two Greek words that refer to its heavy jaw...

s. 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. Polar bears hunt primarily at the interface between ice, water, and air; they only rarely catch seals on land or in open water.

The polar bear's most common hunting method is called still-hunting: The bear uses its excellent sense of smell to locate a seal breathing hole, and crouches nearby in silence for a seal to appear. When the seal exhales, the bear smells its breath, reaches into the hole with a forepaw, and drags it out onto the ice. The polar bear kills the seal by biting its head to crush its skull. The polar bear also hunts by stalking seals resting on the ice: Upon spotting a seal, it walks to within 100 yd (91.4 m), and then crouches. If the seal does not notice, the bear creeps to within 30 to 40 ft (9.1 to 12.2 ) of the seal and then suddenly rushes forth to attack. A third hunting method is to raid the birth lairs that female seals create in the snow.

A widespread legend tells that polar bears cover their black noses with their paws when hunting. This behavior, if it happens, is rare — although the story exists in native oral history
Oral history
Oral history is the collection and study of historical information about individuals, families, important events, or everyday life using audiotapes, videotapes, or transcriptions of planned interviews...

 and in accounts by early Arctic explorers
Arctic exploration
Arctic exploration is the physical exploration of the Arctic region of the Earth. The region that surrounds the North Pole. It refers to the historical period during which mankind has explored the region north of the Arctic Circle...

, there is no record of an eyewitness account of the behavior in recent decades.


Mature bears tend to eat only the calorie-rich skin and blubber of the seal, whereas younger bears consume the protein-rich red meat. Studies have also photographed polar bears scaling near-vertical cliffs, to eat birds' chicks and eggs. For subadult
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...

 bears which are independent of their mother but have not yet gained enough experience and body size to successfully hunt seals, scavenging the carcasses from other bears' kills is an important source of nutrition. Subadults may also be forced to accept a half-eaten carcass if they kill a seal but cannot defend it from larger polar bears. After feeding, polar bears wash themselves with water or snow.

The polar bear is an enormously powerful predator. It can kill an adult walrus
Walrus
The walrus is a large flippered marine mammal with a discontinuous circumpolar distribution in the Arctic Ocean and sub-Arctic seas of the Northern Hemisphere. The walrus is the only living species in the Odobenidae family and Odobenus genus. It is subdivided into three subspecies: the Atlantic...

, although this is rarely attempted. A walrus can be more than twice the bear's weight, and has up to three feet long ivory tusks that can be used as formidable weapons. Polar bears also have been seen to prey on beluga whales, by swiping at them at breathing holes. The whales are of similar size to the walrus and nearly as difficult for the bear to subdue. Polar bears very seldom attack full-grown adult whales. Most terrestrial animals in the Arctic can outrun the polar bear on land as polar bears overheat quickly, and most marine animals the bear encounters can outswim it. In some areas, the polar bear's diet is supplemented by walrus calves and by the carcasses of dead adult walruses or whales, whose blubber is readily devoured even when rotten.
With the exception of pregnant females, polar bears are active year-round, although they have a vestigial hibernation induction trigger
Hibernation induction trigger
Hibernation induction trigger is a substance found in the blood of hibernating animals. If blood is taken from a hibernating squirrel in the winter and injected into another squirrel in the spring, the normally active squirrel will be more prone to hibernation when placed in cold dark conditions...

 in their blood. Unlike brown and black bears, polar bears are capable of fasting
Fasting
Fasting is primarily the act of willingly abstaining from some or all food, drink, or both, for a period of time. An absolute fast is normally defined as abstinence from all food and liquid for a defined period, usually a single day , or several days. Other fasts may be only partially restrictive,...

 for up to several months during late summer and early fall, when they cannot hunt for seals because the sea is unfrozen. When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time. Polar bears have also been observed to eat a wide variety of other wild foods, including muskox, reindeer
Reindeer
The reindeer , also known as the caribou in North America, is a deer from the Arctic and Subarctic, including both resident and migratory populations. While overall widespread and numerous, some of its subspecies are rare and one has already gone extinct.Reindeer vary considerably in color and size...

, birds, eggs, rodents, shellfish, crabs, and other polar bears. They may also eat plants, including berries
Berry
The botanical definition of a berry is a fleshy fruit produced from a single ovary. Grapes are an example. The berry is the most common type of fleshy fruit in which the entire ovary wall ripens into an edible pericarp. They may have one or more carpels with a thin covering and fleshy interiors....

, roots, and kelp
Kelp
Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

, however none of these are a significant part of their diet. 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.

Being both curious animals and scavengers, polar bears investigate and consume garbage
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...

 where they come into contact with humans. Polar bears may attempt to consume almost anything they can find, including hazardous substances such as styrofoam
Styrofoam
Styrofoam is a trademark of The Dow Chemical Company for closed-cell currently made for thermal insulation and craft applications. In 1941, researchers in Dow's Chemical Physics Lab found a way to make foamed polystyrene...

, plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

, car batteries
Car battery
An automotive battery is a type of rechargeable battery that supplies electric energy to an automobile. Usually this refers to an SLI battery to power the starter motor, the lights, and the ignition system of a vehicle’s engine...

, ethylene glycol
Ethylene glycol
Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...

, hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...

, and motor oil
Motor oil
Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is to lubricate moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts.Motor oils are derived from...

. The dump
Landfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

 in Churchill
Churchill, Manitoba
Churchill is a town on the shore of Hudson Bay in Manitoba, Canada. It is most famous for the many polar bears that move toward the shore from inland in the autumn, leading to the nickname "Polar Bear Capital of the World" that has helped its growing tourism industry.-History:A variety of nomadic...

, Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...

 was closed in 2006 to protect bears, and waste is now recycled or transported to Thompson, Manitoba
Thompson, Manitoba
Thompson is a city in northern Manitoba. As the "Hub of the North" it serves as the regional trade and service centre of northern Manitoba. Thompson is located north of the Canada – United States border, north of the provincial capital of Winnipeg, and is northeast of Flin Flon...

.

Behavior



Unlike grizzly bears, polar bears are not territorial
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...

. Although stereotyped as being voraciously aggressive, they are normally cautious in confrontations, and often choose to escape rather than fight. Satiated 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. Whereas brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

s often maul a person and then leave, polar bear attacks are more likely to be predatory and are almost always fatal. However, due to the very small human population around the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

, such attacks are rare.

In general, adult polar bears live solitary lives. Yet, they have often been seen playing together for hours at a time and even sleeping in an embrace, and polar bear zoologist Nikita Ovsianikov has described adult males as having "well-developed friendships." Cubs are especially playful as well. Among young males in particular, play-fighting may be a means of practicing for serious competition during mating seasons later in life. Polar bears have a wide range of vocalisations, including bellows, roars, growls, chuffs and purrs.

In 1992, a photographer near Churchill took a now widely circulated set of photographs of a polar bear playing with a Canadian Eskimo Dog
Canadian Eskimo Dog
The Canadian Eskimo Dog is an Arctic breed of dog , which is often considered to be North America’s oldest and rarest remaining purebred indigenous domestic canine. Other names include Qimmiq...

 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 is far more typical for polar bears to behave aggressively towards dogs.

Reproduction and lifecycle



Courtship and mating take place on the sea ice in April and May, when polar bears congregate in the best seal hunting areas. A male may follow the tracks of a breeding female for 100 km (62.1 mi) or more, and after finding her engage in intense fighting with other males over mating rights, fights which often result in scars and broken teeth. Polar bears have a generally polygynous
Polygyny
Polygyny is a form of marriage in which a man has two or more wives at the same time. In countries where the practice is illegal, the man is referred to as a bigamist or a polygamist...

 mating system; recent genetic testing of mothers and cubs, however, has uncovered cases of litters in which cubs have different fathers. Partners stay together and mate repeatedly for an entire week; the mating ritual induces ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...

 in the female.

After mating, the fertilized egg remains in a suspended state until August or September. During these four months, the pregnant female eats prodigious amounts of food, gaining at least 200 kg (440.9 lb) and often more than doubling her body weight.

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. Most maternity dens are in snowdrifts, but may also be made underground in permafrost
Permafrost
In geology, permafrost, cryotic soil or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of...

 if it is not sufficiently cold yet for snow. In most subpopulations, maternity dens are situated on land a few kilometers from the coast, and the individuals in a subpopulation tend to reuse the same denning areas each year. The polar bears that do not den on land make their dens on the sea ice. In the den, she enters a dormant state similar to hibernation
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...

. This hibernation-like state does not consist of continuous sleeping; however, the bear's heart rate slows from 46 to 27 beats per minute. Her body temperature does not decrease during this period as it would for a typical mammal in hibernation.

Between November and February, cubs are born blind, covered with a light down fur, and weighing less than 0.9 kg (2 lb), but in captivity they might be delivered in the earlier months. The earliest recorded birth of polar bears in captivity was on October 11, 2011 in the Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...

 Zoo. On average, each litter has two cubs. 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. By the time the mother breaks open the entrance to the den, her cubs weigh about 10 to 15 kg (22 to 33.1 ). 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. Then they begin the long walk from the denning area to the sea ice, where the mother can once again catch seals. Depending on the timing of ice-floe breakup in the fall, she may have fasted for up to eight months.
Cubs may fall prey to wolves or to starvation. Female polar bears are noted for both their affection towards their offspring, and their valiance in protecting them. One case of adoption of a wild cub has been confirmed by genetic testing. Adult male bears occasionally kill and eat polar bear cubs, for reasons that are unclear. As of 2006, in Alaska, 42% of cubs now reach 12 months of age, down from 65% 15 years ago. In most areas, cubs are weaned
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...

 at two and a half years of age, 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. This was the case for 40% of cubs there in the early 1980s; however by the 1990s, fewer than 20% of cubs were weaned this young. After the mother leaves, sibling cubs sometimes travel and share food together for weeks or months.

Later life


Females begin to breed at the age of four years in most areas, and five years in the Beaufort Sea area. 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. A study in Hudson Bay indicated that both the reproductive success and the maternal weight of females peaked in their mid-teens.

Polar bears appear to be less affected by infectious diseases and parasites than most terrestrial mammals. Polar bears are especially susceptible to Trichinella
Trichinella
Trichinella is the genus of parasitic roundworms of the phylum Nematoda that cause trichinosis . Members of this genus are often called trichinella or trichina worms...

, a parasitic roundworm they contract through cannibalism
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...

, although infections are usually not fatal. Only one case of a polar bear with rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

 has been documented, even though polar bears frequently interact with Arctic foxes, which often carry rabies. Bacterial Leptospirosis
Leptospirosis
Leptospirosis is caused by infection with bacteria of the genus Leptospira, and affects humans as well as other mammals, birds, amphibians, and reptiles.The...

 and Morbillivirus
Morbillivirus
Morbillivirus is a genus belonging to the Paramyxoviridae family of viruses in the order Mononegavirales. Many members of the genus cause diseases, such as rinderpest and measles, and are highly infectious.- External links :* *...

 have been recorded. Polar bears sometimes have problems with various skin diseases which may be caused by mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...

s or other parasites.

Life expectancy


Polar bears rarely live beyond 25 years. The oldest wild bears on record died at the age of 32, whereas the oldest captive was a female who died in 1991 at the age of 43. The oldest living polar bear was Debby of the Assiniboine Park
Assiniboine Park
Assiniboine Park is a park in Winnipeg, Manitoba. It was established in 1904 and is located north of the Assiniboine Forest. Today, it covers , of these are designed in the English landscape style....

 Zoo, who was probably born in December 1966 and died on November 17, 2008. The causes of death in wild adult polar bears are poorly understood, as carcasses are rarely found in the species's frigid habitat. In the wild, old polar bears eventually become too weak to catch food, and gradually starve to death. Polar bears injured in fights or accidents may either die from their injuries or become unable to hunt effectively, leading to starvation.

Ecological role


The polar bear is the apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...

 within its range. Several animal species, particularly Arctic Fox
Arctic fox
The arctic fox , also known as the white fox, polar fox or snow fox, is a small fox native to Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. The Greek word alopex, means a fox and Vulpes is the Latin version...

es and Glaucous Gull
Glaucous Gull
The Glaucous Gull is a large gull which breeds in the Arctic regions of the northern hemisphere and the Atlantic coasts of Europe. It is migratory, wintering from in the North Atlantic and North Pacific oceans as far south as the British Isles and northernmost states of the USA, also on the Great...

s, routinely scavenge polar bear kills.

The relationship between ringed seals and polar bears is so close that the abundance of ringed seals in some areas appears to regulate the density of polar bears, while polar bear predation in turn, regulates density and reproductive success of ringed seals. The evolutionary pressure
Evolutionary pressure
Any cause that reduces reproductive success in a proportion of a population, potentially exerts evolutionary pressure or selection pressure. With sufficient pressure, inherited traits that mitigate its effects - even if they would be deleterious in other circumstances - can become widely spread...

 of polar bear predation on seals probably accounts for some significant differences between Arctic and Antarctic seals. 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. 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.

Polar bears rarely enter conflict with other predators, though recent brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

 encroachments into polar bear territories have led to antagonistic encounters. Brown bears tend to dominate polar bears in disputes over carcasses, and dead polar bear cubs have been found in brown bear dens. Wolves are rarely encountered by polar bears, though there are two records of wolf packs killing polar bear cubs. Polar bears are sometimes the host of arctic mites such as Alaskozetes antarcticus
Alaskozetes antarcticus
Alaskozetes antarcticus is a species of non-parasitic mite, known for its ability to survive in subzero temperatures.This animal's name derives from its habitat: Alasko, meaning "from Alaska", and antarcticus, in connection with frigid conditions in which the mite lives...

.

Indigenous people



Polar bears have long provided important raw materials for Arctic peoples, including the Inuit, Yupik, Chukchi
Chukchi people
The Chukchi, or Chukchee , ) are an indigenous people inhabiting the Chukchi Peninsula and the shores of the Chukchi Sea and the Bering Sea region of the Arctic Ocean within the Russian Federation. They speak the Chukchi language...

, Nenets
Nenets people
The Nenets are an indigenous people in Russia. According to the latest census in 2002, there are 41,302 Nenets in the Russian Federation, most of them living in the Yamalo-Nenets Autonomous Okrug and Nenets Autonomous Okrug...

, Russian Pomors
Pomors
Pomors or Pomory are Russian settlers and their descendants on the White Sea coast. It is also term of self-identification for the descendants of Russian, primarily Novgorod, settlers of Pomorye , living on the White Sea coasts and the territory whose southern border lies on a watershed which...

 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. Almost all parts of captured animals had a use. The fur was used in particular to sew trousers and, by the Nenets, to make galoshes-like outer footwear called tobok; the meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

 is edible, despite some risk of trichinosis
Trichinosis
Trichinosis, also called trichinellosis, or trichiniasis, is a parasitic disease caused by eating raw or undercooked pork or wild game infected with the larvae of a species of roundworm Trichinella spiralis, commonly called the trichina worm. There are eight Trichinella species; five are...

; the fat was used in food and as a fuel for lighting homes, alongside seal and whale blubber; sinews
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

 were used as thread for sewing clothes; the gallbladder
Gallbladder
In vertebrates the gallbladder is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver. In humans the loss of the gallbladder is usually easily tolerated....

 and sometimes heart were dried and powdered for medicinal purposes; the large canine teeth were highly valued as talismans
Amulet
An amulet, similar to a talisman , is any object intended to bring good luck or protection to its owner.Potential amulets include gems, especially engraved gems, statues, coins, drawings, pendants, rings, plants and animals; even words said in certain occasions—for example: vade retro satana—, to...

. Only the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 was not used, as its high concentration of vitamin A
Retinol
Retinol is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertible to other forms of vitamin A, and the retinyl ester derivative of the alcohol serves as the storage form of the vitamin in animals....

 is poisonous. 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.

History of commercial harvest


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. 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. 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
Spitsbergen
Spitsbergen is the largest and only permanently populated island of the Svalbard archipelago in Norway. Constituting the western-most bulk of the archipelago, it borders the Arctic Ocean, the Norwegian Sea and the Greenland Sea...

 harvested 150 polar bears in Magdalenefjorden
Magdalenefjorden
Magdalenefjorden is an 8 km long and up to 5 km wide fjord between Reuschhalvøya and Hoelhalvøya, Albert I Land, on the west coast of Spitsbergen, the largest island in the Svalbard archipelago.-History:...

. 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.

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. Polar bears were chased from snowmobile
Snowmobile
A snowmobile, also known in some places as a snowmachine, or sled,is a land vehicle for winter travel on snow. Designed to be operated on snow and ice, they require no road or trail. Design variations enable some machines to operate in deep snow or forests; most are used on open terrain, including...

s, icebreaker
Icebreaker
An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters. Although the term usually refers to ice-breaking ships, it may also refer to smaller vessels .For a ship to be considered an icebreaker, it requires three traits most...

s, and airplanes, the latter practice described in a 1965 New York Times editorial as being "about as sporting as machine gunning a cow."
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. 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. The United States began regulating hunting in 1971 and adopted the Marine Mammal Protection Act
Marine Mammal Protection Act
The Marine Mammal Protection Act of 1972 was the first article of legislation to call specifically for an ecosystem approach to natural resource management and conservation. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal,...

 in 1972. In 1973, the International Agreement on the Conservation of Polar Bears
International Agreement on the Conservation of Polar Bears
The International Agreement on the Conservation of Polar Bears was signed in Oslo, November 15, 1973 by the five nations with the largest polar bear populations including Canada, Denmark, Greenland, Norway, the United States, and the former U.S.S.R...

 was signed by all five nations whose territory is inhabited by polar bears Canada, Denmark, Norway, the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

, and the United States. 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". 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
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

. Biologist Ian Stirling
Ian Stirling
Ian Stirling, OC, FRSC is a Scientist Emeritus with the Canadian Wildlife Service. His research has focused mostly on Arctic and Antarctic zoology and ecology, and he is one of the world's top authorities on polar bears....

 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."

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
Chukotka Autonomous Okrug
Chukotka Autonomous Okrug , or Chukotka , is a federal subject of Russia located in the Russian Far East.Chukotka has a population of 53,824 according to the 2002 Census, and a surface area of . The principal town and the administrative center is Anadyr...

. The treaty was ratified in October 2007.

Russia


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. 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. 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
World Wide Fund for Nature
The World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...

 as a means to curb poaching.

Greenland


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

Canada and the United States



About 500 bears are killed per year by humans across Canada, a rate believed by scientists to be unsustainable for some areas, notably Baffin Bay
Baffin Bay
Baffin Bay , located between Baffin Island and the southwest coast of Greenland, is a marginal sea of the North Atlantic Ocean. It is connected to the Atlantic via Davis Strait and the Labrador Sea...

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

On 15 May 2008, the United States listed the polar bear as a threatened species under the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...

 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, permits from the United States Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...

 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. Since 1994, more than 800 sport-hunted polar bear trophies have been imported into the U.S.

The territory of Nunavut
Nunavut
Nunavut is the largest and newest federal territory of Canada; it was separated officially from the Northwest Territories on April 1, 1999, via the Nunavut Act and the Nunavut Land Claims Agreement Act, though the actual boundaries had been established in 1993...

 accounts for the location 80% of annual kills in Canada. In 2005, the government of Nunavut increased the quota from 400 to 518 bears, 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. 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)
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. 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. The Government of the Northwest Territories
Northwest Territories
The Northwest Territories is a federal territory of Canada.Located in northern Canada, the territory borders Canada's two other territories, Yukon to the west and Nunavut to the east, and three provinces: British Columbia to the southwest, and Alberta and Saskatchewan to the south...

 maintain their own quota of 72–103 bears within the Inuvialuit
Inuvialuit
The Inuvialuit or Western Canadian Inuit are Inuit people who live in the western Canadian Arctic region. They, like all other Inuit, are descendants of the Thule who migrated eastward from Alaska...

 communities of which some are set aside for sports hunters. Environment Canada
Environment Canada
Environment Canada , legally incorporated as the Department of the Environment under the Department of the Environment Act Environment Canada (EC) (French: Environnement Canada), legally incorporated as the Department of the Environment under the Department of the Environment Act Environment...

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

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

Conservation status, efforts and controversies


As of 2008, the World Conservation Union
World Conservation Union
The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...

 (IUCN) reports that the global population of polar bears is 20,000 to 25,000, and is declining. In 2006, the IUCN upgraded the polar bear from a species of least concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

 to a vulnerable species
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...

. It cited a "suspected population reduction of >30% within three generations (45 years)", due primarily to climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

. Other risks to the polar bear include pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 in the form of toxic contaminants, conflicts with shipping, stresses from recreational polar-bear watching, and oil and gas exploration and development. The IUCN also cited a "potential risk of over-harvest" through legal and illegal hunting.

According to the World Wildlife Fund, the polar bear is important as an indicator of arctic ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

 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.

Climate change


The IUCN, Arctic Climate Impact Assessment
Arctic Climate Impact Assessment
The Arctic Climate Impact Assessment is a study describing the ongoing climate change in the Arctic and its consequences: rising temperatures, loss of sea ice, unprecedented melting of the Greenland ice sheet, and many impacts on ecosystems, animals, and people...

, United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

 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
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

. 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. Reduction in sea-ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning
Drowning
Drowning is death from asphyxia due to suffocation caused by water entering the lungs and preventing the absorption of oxygen leading to cerebral hypoxia....

. Thinner sea ice tends to deform more easily, which appears to make it more difficult for polar bears to access seals. 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: Changes in sea ice affect the ability of pregnant females to build suitable maternity dens. As the distance increases between the pack ice and the coast, females must swim longer distances to reach favored denning areas on land. 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. 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. Disease-causing bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and parasites would flourish more readily in a warmer climate.

Problematic interactions between polar bears and humans, such as foraging by bears in garbage dumps, have historically been more prevalent in years when ice-floe breakup occurred early and local polar bears were relatively thin. Increased human-bear interactions, including fatal attacks on humans, are likely to increase as the sea ice shrinks and hungry bears try to find food on land.


The effects of climate change 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. The Western Hudson Bay subpopulation, in a southern part of the range, also happens to be one of the best-studied polar bear subpopulations. This subpopulation feeds heavily on ringed seals in late spring, when newly weaned and easily hunted seal pups are abundant. The late spring hunting season ends for polar bears when the ice begins to melt and break up, and they fast or eat little during the summer until the sea freezes again.

Due to warming air temperatures, ice-floe breakup in western Hudson Bay is currently occurring three weeks earlier than it did 30 years ago, reducing the duration of the polar bear feeding season. The body condition of polar bears has declined during this period; the average weight of lone (and likely pregnant) female polar bears was approximately 290 kg (639.3 lb) in 1980 and 230 kg (507.1 lb) in 2004. Between 1987 and 2004, the Western Hudson Bay population declined by 22%.

In Alaska, the effects of sea ice shrinkage
Arctic shrinkage
Ongoing changes in the climate of the Arctic include rising temperatures, loss of sea ice, and melting of the Greenland ice sheet. Projections of sea ice loss suggest that the Arctic ocean will likely be free of summer sea ice sometime between 2060 and 2080, while another estimate puts this date at...

 have contributed to higher mortality rates in polar bear cubs, and have led to changes in the denning locations of pregnant females. In recent years, 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.

Pollution


Polar bears accumulate
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...

 high levels of persistent organic pollutant
Persistent organic pollutant
thumb|right|275px|State parties to the Stockholm Convention on Persistent Organic PollutantsPersistent organic pollutants are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes...

s such as polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...

 (PCBs) and chlorinated pesticides. Due to their position at the top of the food pyramid
Ecological pyramid
thumb|300px|right|An ecological pyramid.An ecological pyramid is a graphical representation designed to show the biomass or biomass productivity at each trophic level in a given ecosystem....

, with a diet heavy in blubber
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...

 in which halocarbons concentrate, their bodies are among the most contaminated of Arctic mammals. Halocarbons are known to be toxic to other animals because they mimic hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

 chemistry, and biomarkers such as immunoglobulin G
Immunoglobulin G
Immunoglobulin G are antibody molecules. Each IgG is composed of four peptide chains — two heavy chains γ and two light chains. Each IgG has two antigen binding sites. Other immunoglobulins may be described in terms of polymers with the IgG structure considered the monomer.IgG constitutes 75%...

 and retinol suggest similar effects on polar bears. PCBs have received the most study, and they have been associated with birth defects and immune system deficiency.

The most notorious of these chemicals, such as PCBs and DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....

, have been internationally banned. Their concentrations in polar bear tissues continued to rise for decades after the ban as these chemicals spread through the food chain. But the trend seems to have abated, with tissue concentrations of PCBs declining between studies performed in 1989–1993 and studies performed in 1996–2002.

Oil and gas development



Oil and gas development in polar bear habitat can affect the bears in a variety of ways. An oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...

 in the Arctic would most likely concentrate in the areas where polar bears and their prey are also concentrated, such as sea ice leads. Because polar bears rely partly on their fur for insulation and soiling of the fur by oil reduces its insulative value, oil spills put bears at risk of dying from hypothermia
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

. Polar bears exposed to oil spill conditions have been observed to lick the oil from their fur, leading to fatal kidney failure. Maternity dens, used by pregnant females and by females with infants, can also be disturbed by nearby oil exploration and development. Disturbance of these sensitive sites may trigger the mother to abandon her den prematurely, or abandon her litter altogether.

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 climate change. 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.

Predictions vary on the extent to which polar bears could adapt to climate change by switching to terrestrial food sources. Mitchell Taylor, who was director of Wildlife Research for the Government of Nunavut, wrote to the US 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." Ken Taylor, deputy commissioner for the Alaska Department of Fish and Game
Alaska Department of Fish and Game
The Alaska Department of Fish and Game is a department within the government of Alaska. The Department of Fish and Game manages Alaska's fish, game, and aquatic plant resources.-History:...

, has said, "I wouldn't be surprised if polar bears learned to feed on spawning salmon like grizzly bears."

However, many scientists consider these theories to be naive; it is noted that black and brown bears at high latitudes are smaller than elsewhere, because of the scarcity of terrestrial food resources. An additional risk to the species is that if individuals spend more time on land, they will hybridize with brown or grizzly bears. The IUCN wrote:

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.

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. Second, controls of harvesting were introduced that allowed this previously overhunted species to recover. Third, the recent effects of climate change have affected sea ice abundance in different areas to varying degrees.

Debate over the listing of the polar bear under endangered species legislation has put conservation groups and Canada's Inuit
Inuit
The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 at opposing positions; the Nunavut
Nunavut
Nunavut is the largest and newest federal territory of Canada; it was separated officially from the Northwest Territories on April 1, 1999, via the Nunavut Act and the Nunavut Land Claims Agreement Act, though the actual boundaries had been established in 1993...

 government and many northern residents have condemned the U.S. initiative to list the polar bear under the Endangered Species Act. Many Inuit believe the polar bear population is increasing, and restrictions on sport-hunting are likely to lead to a loss of income to their communities.

U.S. endangered species legislation


On 14 May 2008 the U.S. Department of the Interior listed the polar bear as a threatened species under the Endangered Species Act, citing the melting of Arctic sea ice as the primary threat to the polar bear. While listing the polar bear as a threatened species, the Interior Department added a seldom-used stipulation to allow oil and gas exploration and development to proceed in areas inhabited by polar bears, provided companies continue to comply with the existing restrictions of the Marine Mammal Protection Act. The main new protection for polar bears under the terms of the listing is that hunters will no longer be able to import trophies from the hunting of polar bears in Canada.

The ruling followed several years of controversy. On 17 February 2005 the Center for Biological Diversity
Center for Biological Diversity
The Center for Biological Diversity based in Tucson, Arizona, is a nonprofit membership organization with approximately 220,000 members and online activists, known for its work protecting endangered species through legal action and scientific petitions...

 filed a petition asking that the polar bear be listed under the Endangered Species Act. An agreement was reached and filed in Federal district court on 5 June 2006. On 9 January 2007, the US Fish and Wildlife Service proposed to list the polar bear as a threatened species. A final decision was required by law by 9 January 2008, at which time the agency said it needed another month. On 7 March 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. The auction took place in early February 2008. An editorial in The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

said that "these two moves are almost certainly, and cynically, related." 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. On 28 April 2008, a Federal court ruled that a decision on the listing must be made by 15 May 2008; the decision came on 14 May to make the polar bear a protected species.

On 18 July 2011, Charles Monnett
Charles Monnett
Charles Monnett, Ph.D. is a Arctic Wildlife biologist with U.S. Bureau of Ocean Energy Management, Regulation and Enforcement , an agency of the U.S...

, whose work was cited by the U.S. Fish and Wildlife Service in its decision to list the polar bear as threatened under the Endangered Species Act, was suspended from his work at the Bureau of Ocean Energy Management, Regulation and Enforcement. Investigators are reviewing Monnett's research methods as well as the significance he attached to his discovery in 2004 of polar bear carcasses in the Arctic, but supporters argue that the investigation is essentially "a smear campaign" against Monnett.

Upon listing the polar bear under the Endangered species act, the Department of the Interior immediately issued a statement that the listing could not be used to regulate greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 emissions, although some policy analysts believe that the Endangered Species Act can be used to restrict the issuing of federal permits for projects that would threaten the polar bear by increasing greenhouse gas emissions. Environmental groups have pledged to go to court to have the Endangered Species Act interpreted in such a way. On 8 May 2009, the new administration of Barack Obama announced that it would continue the policy. The polar bear is only the third species, after the elkhorn coral
Elkhorn coral
Elkhorn coral is considered to be one of the most important reef-building corals in the Caribbean. This species of coral is structurally complex with many large branches. The coral structure closely resembles that of elk antlers. These branches create habitats for many other reef species such as...

 and the staghorn coral
Staghorn coral
The Staghorn coral is a branching coral with cylindrical branches ranging from a few centimetres to over two metres in length and height. It occurs in back reef and fore reef environments from 0 to 30 m depth. The upper limit is defined by wave forces, and the lower limit is controlled by...

 protected under the Endangered Species Act due to climate change. On 4 August 2008, the state of Alaska sued U.S. Interior Secretary Dirk Kempthorne
Dirk Kempthorne
Dirk Arthur Kempthorne , was the U.S. Secretary of the Interior, who served under President George W. Bush from 2006 to 2009. A Republican, Kempthorne previously served as the 30th Governor and as a U.S. Senator from Idaho...

, seeking to reverse the listing of the polar bear as a threatened species out of concern that the listing would adversely affect oil and gas development in the state. Alaska Governor Sarah Palin
Sarah Palin
Sarah Louise Palin is an American politician, commentator and author. As the Republican Party nominee for Vice President in the 2008 presidential election, she was the first Alaskan on the national ticket of a major party and first Republican woman nominated for the vice-presidency.She was...

 said that the listing was not based on the best scientific and commercial data available, a view rejected by polar bear experts.

Canadian endangered species legislation


In Canada, the Committee on the Status of Endangered Wildlife in Canada
Committee on the Status of Endangered Wildlife in Canada
The Committee on the Status of Endangered Wildlife in Canada ; French: Le Comité sur la situation des espèces en péril au Canada, is an independent committee of wildlife experts and scientists whose "raison d’être is to identify species at risk" in Canada...

 recommended in April 2008 that the polar bear be assessed as a species of special concern under the federal Species at Risk Act
Species at Risk Act
The Species at Risk Act is a piece of Canadian federal legislation which became law in Canada on December 12, 2002. It is designed to meet one of Canada's key commitments under the International Convention on Biological Diversity. The goal of the Act is to protect endangered or threatened...

 (SARA). A listing would mandate that a management plan be written within five years, a timeline criticized by the World Wide Fund for Nature as being too long to prevent significant habitat loss from climate change.

In culture



Indigenous folklore


For the indigenous peoples of the Arctic, polar bears have long played an important cultural and material role. Polar bear remains have been found at hunting sites dating to 2,500 to 3,000 years ago and 1,500 year old cave painting
Cave painting
Cave paintings are paintings on cave walls and ceilings, and the term is used especially for those dating to prehistoric times. The earliest European cave paintings date to the Aurignacian, some 32,000 years ago. The purpose of the paleolithic cave paintings is not known...

s of polar bears have been found in the Chukchi Peninsula
Chukchi Peninsula
The Chukchi Peninsula, Chukotka Peninsula or Chukotski Peninsula , at about 66° N 172° W, is the northeastern extremity of Asia. Its eastern end is at Cape Dezhnev near the village of Uelen. It is bordered by the Chukchi Sea to the north, the Bering Sea to the south, and the Bering Strait to the...

. Indeed, it has been suggested that Arctic peoples' skills in seal hunting and igloo
Igloo
An igloo or snowhouse is a type of shelter built of snow, originally built by the Inuit....

 construction has been in part acquired from the polar bears themselves.

The Inuit
Inuit
The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 and Eskimo
Eskimo
Eskimos or Inuit–Yupik peoples are indigenous peoples who have traditionally inhabited the circumpolar region from eastern Siberia , across Alaska , Canada, and Greenland....

s have many folk tales
Folklore
Folklore consists of legends, music, oral history, proverbs, jokes, popular beliefs, fairy tales and customs that are the traditions of a culture, subculture, or group. It is also the set of practices through which those expressive genres are shared. The study of folklore is sometimes called...

 featuring the bears including legends in which bears are humans when inside their own houses and put on bear hides when going outside, and stories of how the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 which is said to resemble a great bear surrounded by dogs came into being. These legends reveal a deep respect for the polar bear, which is portrayed as both spiritually powerful and closely akin to humans. The human-like posture of bears when standing and sitting, and the resemblance of a skinned bear carcass to the human body, have probably contributed to the belief that the spirits of humans and bears were interchangeable. Eskimo legends tell of humans learning to hunt from the polar bear. For the Inuit of Labrador, the polar bear is a form of the Great Spirit, Tuurngasuk.

Among the Chukchi
Chukchi people
The Chukchi, or Chukchee , ) are an indigenous people inhabiting the Chukchi Peninsula and the shores of the Chukchi Sea and the Bering Sea region of the Arctic Ocean within the Russian Federation. They speak the Chukchi language...

 and Yupik
Siberian Yupik
Siberian Yupiks, or Yuits, are indigenous people who reside along the coast of the Chukchi Peninsula in the far northeast of the Russian Federation and on St. Lawrence Island in Alaska. They speak Central Siberian Yupik , a Yupik language of the Eskimo–Aleut family of languages.They were also...

 of eastern Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

, there was a longstanding shamanistic ritual
Shamanism among Eskimo peoples
Shamanism among Eskimo peoples refers to those aspects of the various Eskimo cultures that are related to the shamans’ role as a mediator between people and spirits, souls, and mythological beings...

 of "thanksgiving" to the hunted polar bear. After killing the animal, its head and skin were removed and cleaned and brought into the home, a feast was held 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. 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. Many of these traditions have faded somewhat in time, especially in light of the total hunting ban in the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 (and now Russia) since 1955.

The Nenets of north-central Siberia placed particular value on the talismanic power of the prominent canine teeth. They were traded in the villages of the lower Yenisei
Yenisei River
Yenisei , also written as Yenisey, is the largest river system flowing to the Arctic Ocean. It is the central of the three great Siberian rivers that flow into the Arctic Ocean...

 and Khatanga
Khatanga River
The Khatanga River is a river in Krasnoyarsk Krai in Russia. It begins at the confluence of the rivers Kotuy and Kheta. The Khatanga River is long; the area of its basin is 364,000 km². It flows into the Khatanga Gulf of the Laptev Sea, forming an estuary...

 rivers to the forest-dwelling peoples further south, who would sew them into their hats as protection against brown bear
Brown Bear
The brown bear is a large bear distributed across much of northern Eurasia and North America. It can weigh from and its largest subspecies, the Kodiak Bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.There are several recognized...

s. 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). The skulls of killed polar bears were buried at specific sacred sites and altars, called sedyangi, were constructed out of the skulls. Several such sites have been preserved on the Yamal Peninsula
Yamal Peninsula
The Yamal Peninsula , located in Yamal-Nenets autonomous district of northwest Siberia, Russia, extends roughly 700 km and is bordered principally by the Kara Sea, Baydaratskaya Bay on the west, and by the Gulf of Ob on the east...

.

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 Toonie
Toonie
The Canadian 2 dollar coin, commonly called Toonie, was introduced on February 19, 1996 by Public Works minister Diane Marleau. The Toonie is a bi-metallic coin which bears an image of a polar bear, by Campbellford, Ontario artist Brent Townsend, on the reverse. The obverse, like all other current...

 (two-dollar coin) features the image of a polar bear and both the Northwest Territories and Nunavut license plates
Vehicle registration plates of Nunavut
The Canadian territory of Nunavut, established in 1999, splitting from the Northwest Territories, since that time has issued licence plates to motor vehicles registered there...

 in Canada are in the shape of a polar bear. The polar bear is the mascot of Bowdoin College
Bowdoin College
Bowdoin College , founded in 1794, is an elite private liberal arts college located in the coastal Maine town of Brunswick, Maine. As of 2011, U.S. News and World Report ranks Bowdoin 6th among liberal arts colleges in the United States. At times, it was ranked as high as 4th in the country. It is...

 in Maine
Maine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...

 and the University of Alaska Fairbanks
University of Alaska Fairbanks
The University of Alaska Fairbanks, located in Fairbanks, Alaska, USA, is the flagship campus of the University of Alaska System, and is abbreviated as Alaska or UAF....

 (see also Alaska Nanooks
Alaska Nanooks
The Alaska Nanooks are the University of Alaska Fairbanks sports teams, derived from the Inupiaq "nanuq." The school colors are blue and gold. The Nanooks compete at the NCAA Division II level for all sports except men's ice hockey...

) and was chosen as mascot for the 1988 Winter Olympics
1988 Winter Olympics
The 1988 Winter Olympics, officially known as the XV Olympic Winter Games, were a winter multi-sport event celebrated in and around Calgary, Alberta, Canada from 13 to 28 February 1988. The host was selected in 1981 after having beat Falun, Sweden and Cortina d'Ampezzo, Italy...

 held in Calgary
Calgary
Calgary is a city in the Province of Alberta, Canada. It is located in the south of the province, in an area of foothills and prairie, approximately east of the front ranges of the Canadian Rockies...

.

Companies such Coca-Cola
Coca-Cola
Coca-Cola is a carbonated soft drink sold in stores, restaurants, and vending machines in more than 200 countries. It is produced by The Coca-Cola Company of Atlanta, Georgia, and is often referred to simply as Coke...

, Polar Beverages
Polar Beverages
Polar Beverages is a fourth-generation, family-owned business that traces its roots back to 1882 and is based in Worcester, Massachusetts. The company is currently run by Ralph Crowley, Jr., the great-grandson of founder Dennis M. Crowley...

, Nelvana
Nelvana
Nelvana Limited is a Canadian entertainment company founded in 1971 known for its work in children's animation. It was named by founders Michael Hirsh, Patrick Loubert and Clive A. Smith after a Canadian comic book superheroine created by Adrian Dingle in the 1940s...

, Bundaberg Rum
Bundaberg Rum
Bundaberg Rum is a dark rum produced in Bundaberg, Australia, often referred to as "Bundy".The Bundaberg Distilling Company owns its own cola-producing facility, which supplies the cola for its ready-to-drink Bundaberg Rum and Cola products.-History:...

 and Good Humor-Breyers
Klondike bar
Klondike is a brand name for a dessert generally consisting of a vanilla ice cream square coated with a thin layer of chocolate-flavored coating. The first recorded advertisement for the Klondike was on February 5, 1922 in the Youngstown Vindicator. They are generally wrapped with a silver-colored...

 have used images of the polar bear in advertising, while Fox's Glacier Mints
Fox's Glacier Mints
Fox's Glacier Mints are the leading, branded boiled mint in the UK. They have been manufactured by Fox's Confectionery in Leicester since 1918. The mints were developed by Eric Fox, one of the original founders of Fox's Confectionery. Since 1922 the mints have been sold with the Peppy the polar...

 have featured a polar bear named Peppy as the brand mascot since 1922.

Literature


Polar bears are also popular in fiction, particularly in books aimed at children or young adults. For example, The Polar Bear Son is adapted from a traditional Inuit tale
Inuit mythology
Inuit mythology has many similarities to the religions of other polar regions. Inuit traditional religious practices could be very briefly summarised as a form of shamanism based on animist principles....

. Polar bears feature prominently in East
East (novel)
East is a 2003 novel by the author Edith Pattou. It is an adaptation of an old Norwegian folk tale entitled "East of the Sun and West of the Moon" and is an ALA Top Ten Best Book for Young Adults...

(also released as North Child) by Edith Pattou
Edith Pattou
Edith Pattou is the author of several fantasy novels, including East, an ALA Top Ten Best Book for Young Adults. She is a graduate of the Francis W. Parker School, Scripps College , Claremont Graduate School and UCLA . She is married to Charles Emery, a professor of psychology at The Ohio State...

, The Bear by Raymond Briggs
Raymond Briggs
Raymond Redvers Briggs is an English illustrator, cartoonist, graphic novelist, and author who has achieved critical and popular success among adults and children...

, and Chris d'Lacey
Chris D'Lacey
Chris d'Lacey is an English writer of children's fiction.-Biography:Chris d'Lacey was born in Valetta, Malta, but as a child moved first to Leicester and then to Bolton...

's The Fire Within
The Fire Within (novel)
The Fire Within is a 200111 children's fantasy novel written by Chris d'Lacey. It has a sequel named Icefire, which is followed by Fire Star, The Fire Eternal, Dark Fire and Fire World.-Plot summary:...

series. The panserbjørne of Philip Pullman's
Philip Pullman
Philip Pullman CBE, FRSL is an English writer from Norwich. He is the best-selling author of several books, most notably his trilogy of fantasy novels, His Dark Materials, and his fictionalised biography of Jesus, The Good Man Jesus and the Scoundrel Christ...

 fantasy trilogy His Dark Materials
His Dark Materials
His Dark Materials is a trilogy of fantasy novels by Philip Pullman comprising Northern Lights , The Subtle Knife , and The Amber Spyglass...

are sapient, dignified polar bears who exhibit anthropomorphic
Anthropomorphism
Anthropomorphism is any attribution of human characteristics to animals, non-living things, phenomena, material states, objects or abstract concepts, such as organizations, governments, spirits or deities. The term was coined in the mid 1700s...

 qualities, and feature prominently in the 2007 film adaptation of The Golden Compass.

See also


  • Arctic National Wildlife Refuge
    Arctic National Wildlife Refuge
    The Arctic National Wildlife Refuge is a national wildlife refuge in northeastern Alaska, United States. It consists of in the Alaska North Slope region. It is the largest National Wildlife Refuge in the country, slightly larger than the Yukon Delta National Wildlife Refuge...

  • List of solitary animals


External links