View source for Biology:Polar bear

{{Short description|Species of bear native largely to the Arctic Circle}}
{{Use Canadian English|date=December 2015}}
{{Speciesbox
| fossil_range = [[Earth:Pleistocene|Pleistocene]]-recent<ref name="polarresearch"/>
| image = Polar Bear - Alaska (cropped).jpg
| image_caption = Female near Kaktovik, Barter Island, [[Earth:Alaska|Alaska]], {{wipe|United States}}
| status = VU
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Wiig, Ø. |author2=Amstrup, S. |author3=Atwood, T. |author4=Laidre, K. |author5=Lunn, N. |author6=Obbard, M. |author7=Regehr, E. |author8=Thiemann, G. |date=2015 |title=''Ursus maritimus'' |volume=2015 |page=e.T22823A14871490 |doi=10.2305/IUCN.UK.2015-4.RLTS.T22823A14871490.en |access-date=19 November 2021}}</ref>
| status2 = CITES_A2
| status2_system = CITES
| status2_ref = <ref name="CITES">{{Cite web|title=Appendices|url=https://cites.org/eng/app/appendices.php|access-date=2022-01-14|website=cites.org}}</ref>
| genus = Ursus
| species = maritimus
| authority = Phipps, 1774<ref name="Phipps1774"/>
| range_map = Polar bear (range).svg
| range_map_caption = Polar bear range
| synonyms = ''Ursus eogroenlandicus''<br/>
''Ursus groenlandicus''<br/>
''Ursus jenaensis''<br/>
''Ursus labradorensis''<br/>
''Ursus marinus''<br/>
''Ursus polaris''<br/>
''Ursus spitzbergensis''<br/>
''Ursus ungavensis''<br/>
''Thalarctos maritimus''
}}

The '''polar bear''' ('''''Ursus maritimus''''') is a large bear native to the Arctic and nearby areas. It is closely related to the [[Biology:Brown bear|brown bear]], and the two species can interbreed. The polar bear is the largest extant species of bear and land [[Biology:Carnivore|carnivore]], with adult males weighing {{convert|300|–|800|kg|-1|abbr=on}}. The species is [[Biology:Sexual dimorphism|sexually dimorphic]], as adult females are much smaller. The polar bear is white- or yellowish-furred with black skin and a thick layer of fat. It is more slender than the brown bear, with a narrower skull, longer neck and lower shoulder hump. Its teeth are sharper and more adapted to cutting meat. The paws are large and allow the bear to walk on ice and paddle in the water.

Polar bears are both terrestrial and [[Earth:Pagophily|pagophilic]] (ice-living) and are considered to be [[Biology:Marine mammal|marine mammal]]s due to their dependence on [[Earth:Marine ecosystem|marine ecosystem]]s. They prefer the annual [[Earth:Sea ice|sea ice]] but live on land when the ice melts in the summer. They are mostly carnivorous and specialized for preying on [[Biology:Pinniped|seals]], particularly ringed seals. Such prey is typically taken by ambush; the bear may stalk its prey on the ice or in the water, but also will stay at a breathing hole or ice edge to wait for prey to swim by. The bear primarily feeds on the seal's energy-rich blubber. Other prey include [[Biology:Walrus|walrus]]es, [[Biology:Beluga whale|beluga whale]]s and some terrestrial animals. Polar bears are usually solitary but can be found in groups when on land. During the breeding season, male bears guard females and defend them from rivals. Mothers give birth to cubs in [[Biology:Maternity den|maternity den]]s during the winter. Young stay with their mother for up to two and a half years.

The polar bear is considered to be a [[Biology:Vulnerable species|vulnerable species]] by the [[Organization:International Union for Conservation of Nature|International Union for Conservation of Nature]] (IUCN) with an estimated total population of 22,000 to 31,000 individuals. Its biggest threats are [[Earth:Climate change|climate change]], pollution and energy development. Climate change has caused a [[Physics:Arctic sea ice decline|decline in sea ice]], giving the polar bear less access to its favoured prey and increasing the risk of malnutrition and starvation. Less sea ice also means that the bears must spend more time on land, increasing conflicts with people. Polar bears have been hunted, both by native and non-native peoples, for their coats, meat and other items. They have been kept in captivity in [[Biology:Zoo|zoo]]s and circuses and are prevalent in art, folklore, religion and modern culture.

==Naming==
The polar bear was given its common name by Thomas Pennant in ''A Synopsis of Quadrupeds'' (1771). It was known as the "white bear" in Europe between the 13th and 18th centuries, as well as "ice bear", "sea bear" and "[[Place:Greenland|Greenland]] bear". The Norse referred to it as {{lang|no|isbjørn}} ("ice bear") and {{lang|no|hvitebjørn}} ("white bear"). The bear is called {{lang|und|nanook}} by the Inuit. The Netsilik cultures additionally have different names for bears based on certain factors, such as sex and age: these include adult males ({{lang|und|anguraq}}), single adult females ({{lang|und|tattaq}}), gestating females ({{lang|und|arnaluk}}), newborns ({{lang|und|hagliaqtug}}), large adolescents ({{lang|und|namiaq}}) and dormant bears ({{lang|und|apitiliit}}).{{sfn|Engelhard|2017|pp=13, 31, 68–69, 122, 253}} The scientific name ''Ursus maritimus'' is [[Social:Latin|Latin]] for "sea bear".{{sfn|Engelhard|2017|p=48}}{{sfn|Derocher|2012|p=1}}

==Taxonomy==
[[Biography:Carl Linnaeus|Carl Linnaeus]] classified the polar bear as a type of [[Biology:Brown bear|brown bear]] (''Ursus arctos''), labelling it as ''Ursus maritimus albus-major, articus'' in the [[Biology:10th edition of Systema Naturae|1758 edition]] of his work ''[[Biology:Systema Naturae|Systema Naturae]]''.{{sfn|Fee|2019|p=48}} Constantine John Phipps formally described the polar bear as a distinct species, ''Ursus maritimus'' in 1774, following his [[Earth:1773 Phipps expedition towards the North Pole|1773 voyage towards the North Pole]].<ref name="Phipps1774">{{cite book |last=Phipps |first=John |title=A voyage towards the North Pole undertaken by His Majesty's command, 1773 |location=London |publisher=W. Bowyer and J. Nicols, for J. Nourse |year=1774 |url=https://www.biodiversitylibrary.org/page/628763 |page=185 |access-date=13 January 2018 |archive-url=https://web.archive.org/web/20170707094547/http://www.biodiversitylibrary.org/page/628763 |archive-date=7 July 2017 |url-status=dead}}</ref>{{sfn|Fee|2019|p=41}} Due to its adaptations to a marine environment, some taxonomists like Theodore Knottnerus-Meyer have placed the polar bear in its genus ''Thalarctos''.<ref name="DeMaster1981"/>{{sfn|Ellis|2009|p=67}} However ''Ursus'' is widely considered to be the valid genus for the species based on the fossil record and the fact that it [[Biology:Hybrid|can breed]] with the brown bear.{{sfn|Ellis|2009|p=67}}<ref name="ReferenceC"/>

Different [[Biology:Subspecies|subspecies]] have been proposed including ''Ursus maritimus maritimus'' and ''U. m. marinus''.{{efn|Phipps (1774) and Pallas (1776) respectively.<ref name="Wilson1976"/>}}<ref name="Wilson1976">{{cite journal|last1=Wilson|first1=Don E.|title=Cranial variation in polar bears|journal=Bears: Their Biology and Management|date=1976|volume=3|pages=447–453|doi=10.2307/3872793|jstor=3872793}}</ref> However these are not supported and the polar bear is considered to be [[Biology:Monotypic taxon|monotypic]].<ref name=":0">{{Cite web|url=https://www.marinemammalscience.org/species-information/list-of-marine-mammal-species-subspecies/|title=List of Marine Mammal Species & Subspecies|author=Committee on Taxonomy|date=October 2014|publisher=The Society for Marine Mammalogy|archive-url=https://web.archive.org/web/20150106152733/https://www.marinemammalscience.org/species-information/list-of-marine-mammal-species-subspecies/|archive-date=6 January 2015}}</ref> One possible fossil subspecies, ''[[Biology:Ursus maritimus tyrannus|U. m. tyrannus]]'', was posited in 1964 by Björn Kurtén, who reconstructed the subspecies from a single fragment of an ulna which was approximately 20 percent larger than expected for a polar bear.<ref name="ReferenceC"/> However, re-evaluation in the 21st century has indicated that the fragment likely comes from a giant brown bear.<ref name=Harington>{{cite journal|last=Harington|first=C. R.|year=2008|title=The evolution of Arctic marine mammals|journal=Ecological Adapations|volume=18|issue=sp2|pages=S23–S40|doi=10.1890/06-0624.1|pmid=18494361 |doi-access=free|bibcode=2008EcoAp..18S..23H }}</ref>{{sfn|Derocher|2012|p=37}}

===Evolution===
The polar bear is one of eight extant species in the bear family Ursidae and of six extant species in the subfamily Ursinae. A possible [[Biology:Phylogenetic tree|phylogeny]] of extant bear species is shown in a cladogram based on complete [[Biology:Mitochondrial DNA|mitochondrial DNA]] sequences from Yu ''et al''.&nbsp;(2007).<ref>{{cite journal |last1=Yu |first1=Li |last2=Li |first2=Yi-Wei |last3=Ryder |first3=Oliver A. |last4=Zhang |first4=Ya-Ping |title=Analysis of complete mitochondrial genome sequences increases phylogenetic resolution of bears (Ursidae), a mammalian family that experienced rapid speciation |journal=BMC Evolutionary Biology |date=2007 |volume=7 |issue=198 |page=198 |doi=10.1186/1471-2148-7-198 |pmid=17956639 |pmc=2151078 |doi-access=free |bibcode=2007BMCEE...7..198Y }}</ref> The polar bear and the brown bear form a close grouping, while the relationships of the other species are not very well resolved.<ref name=Servheen1999>{{cite book |author1=Servheen, C. |author2=Herrero, S. |author3=Peyton, B. |title=Bears: Status Survey and Conservation Action Plan |url=https://portals.iucn.org/library/sites/library/files/documents/1999-004.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://portals.iucn.org/library/sites/library/files/documents/1999-004.pdf |archive-date=2022-10-09 |url-status=live |year=1999 |publisher=IUCN |isbn=978-2-8317-0462-3 |pages=26–30}}</ref>

{{clade|style=font-size:80%;line-height:80%
|label1=[[Biology:Ursidae|Ursidae]]
|1={{clade
   |1=[[Biology:Giant panda|Giant panda]] (''Ailuropoda melanoleuca'') [[File:Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg|50px]]
   |2={{clade
     |1=[[Biology:Spectacled bear|Spectacled bear]] (''Tremarctos ornatus'') [[File:Spectacled bear (1829).jpg|50px]]
     |2={{clade
        |label1=Ursinae
        |1={{clade
           |1=Sloth bear (''Melursus ursinus'') [[File:Tremarctos ornatus 1824 (flipped).jpg|50px]]
           |2={{clade
              |1={{clade
                 |1=Sun bear (''Helarctos malayanus'') [[File:Ursus malayanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
                 |2={{clade
                    |1=Asian black bear (''Ursus thibetanus'') [[File:Ursus thibetanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam -(white background).jpg|50px]]
                    |2=[[Biology:American black bear|American black bear]] (''Ursus americanus'') [[File:Ursus americanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
                    }}
                 }}
              |2={{clade
                 |1=[[Biology:Polar bear|Polar bear]] (''Ursus maritimus'') [[File:Lossy-page1-2518px-Ursus maritimus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
                 |2=[[Biology:Brown bear|Brown bear]] (''Ursus arctos'') [[File:Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
                 }}
              }}

           }}

        }}
      }}
   }}
}}

A more recent phylogeny below is based on a 2017 genetic study. The study concludes that Ursine bears originated around 5 million years ago and show extensive hybridization of species in their lineage.<ref>{{cite journal|last1=Kumar|first1=V.|last2=Lammers|first2=F.|last3=Bidon|first3=T. |last4=Pfenninger|first4=M.|last5=Kolter|first5=L.|last6=Nilsson|first6=M. A.|last7=Janke|first7=A.|year=2017 |title=The evolutionary history of bears is characterized by gene flow across species|journal=Scientific Reports|volume=7|page=46487|doi=10.1038/srep46487|pmid=28422140|pmc=5395953|bibcode=2017NatSR...746487K}}</ref> 
 
{{clade|style=font-size:80%;line-height:80%
|label1=[[Biology:Ursidae|Ursidae]]
|1={{clade
   |1=[[Biology:Giant panda|Giant panda]] (''Ailuropoda melanoleuca'') [[File:Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg|50px]]
   |2={{clade
      |1=[[Biology:Spectacled bear|Spectacled bear]] (''Tremarctos ornatus'') [[File:Spectacled bear (1829).jpg|50px]]
      |label2=Ursinae
      |2={{clade
         |1={{clade
            |1={{clade
               |1=Sloth bear (''Melursus ursinus'') [[File:Tremarctos ornatus 1824 (flipped).jpg|50px]]
               |2=Sun bear (''Helarctos malayanus'') [[File:Ursus malayanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
               }}
            |2=Asian black bear (''Ursus thibetanus'') [[File:Ursus thibetanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam -(white background).jpg|50px]]
            }}
         |2={{clade
            |1=[[Biology:American black bear|American black bear]] (''Ursus americanus'') [[File:Ursus americanus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
            |2={{clade
               |1=[[Biology:Polar bear|Polar bear]] (''Ursus maritimus'') [[File:Lossy-page1-2518px-Ursus maritimus - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
               |2=[[Biology:Brown bear|Brown bear]] (''Ursus arctos'') [[File:Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|50px]]
               }}
            }}
         }}
      }}
   }}
}}

Fossils of polar bears are uncommon.<ref name="ReferenceC">{{cite journal|last1=Kurtén|first1=B.|title=The evolution of the polar bear, ''Ursus maritimus'' Phipps|journal=Acta Zoologica Fennica|date=1964|volume=108|pages=1–30|url=https://helda.helsinki.fi/handle/10138/37762}}</ref><ref name=Harington/> The oldest known fossil is a 130,000- to 110,000-year-old jaw bone, found on Prince Charles Foreland, Norway, in 2004.<ref name="Lindqvist">{{cite journal|doi=10.1073/pnas.0914266107|pmid=20194737|pmc=2841953 |title=Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear |journal=Proceedings of the National Academy of Sciences |volume=107 |issue=11 |pages=5053–5057 |year=2010 |last1=Lindqvist |first1=C. |last2=Schuster |first2=S. C. |last3=Sun |first3=Y. |last4=Talbot |first4=S. L. |last5=Qi |first5=J. |last6=Ratan |first6=A. |last7=Tomsho |first7=L. P. |last8=Kasson |first8=L. |last9=Zeyl |first9=E. |last10=Aars |first10=J. |last11=Miller |first11=W. |last12=Ingolfsson |first12=O. |last13=Bachmann |first13=L. |last14=Wiig |first14=O. |bibcode=2010PNAS..107.5053L|doi-access=free}}</ref><ref name="polarresearch">{{cite journal|last1=Ingólfsson|first1=Ólafur|last2=Wiig|first2=Øystein|title=Late Pleistocene fossil find in Svalbard: the oldest remains of a polar bear (''Ursus maritimus'' Phipps, 1744) ever discovered|journal=Polar Research|date=2009|volume=28|issue=3|pages=455–462|doi=10.3402/polar.v28i3.6131|doi-access=free}}</ref> Scientists in the 20th century surmised that polar bears directly descended from a population of brown bears, possibly in eastern Siberia or [[Earth:Alaska|Alaska]].<ref name="ReferenceC"/><ref name=Harington/> [[Biology:Mitochondrial DNA|Mitochondrial DNA]] studies in the 1990s and 2000s supported the status of the polar bear as a derivative of the brown bear, finding that some brown bear populations were more closely related to polar bears than to other brown bears, particularly the [[Biology:ABC Islands bear|ABC Islands bear]]s of Southeast Alaska.<ref name="Lindqvist"/><ref>{{cite journal|last1=Talbot|first1=S. L.|last2=Shields|first2=G. F.|year=1996|title=Phylogeography of brown bears (''Ursus arctos'') of Alaska and paraphyly within the Ursidae|journal=Molecular Phylogenetics and Evolution|volume=5|issue=3|pages=477–494|doi=10.1006/mpev.1996.0044|pmid=8744762 }}</ref><ref>{{cite journal|last1=Shields|first1=G. F.|last2=Adams|first2=D.|last3=Garner|first3=G.| last4=Labelle|first4=M.|last5=Pietsch|first5=J.|last6=Ramsay|first6=M.| last7=Schwartz|first7=C.|last8=Titus|first8=K.|last9=Williamson|first9=S.|year=2000|title=Phylogeography of mitochondrial DNA variation in brown bears and polar bears|journal=Molecular Phylogenetics and Evolution|volume=15|issue=2|pages=19–26|doi=10.1006/mpev.1999.0730|pmid=10837161 }}</ref> A 2010 study estimated that the polar bear lineage split from other brown bears around 150,000 years ago.<ref name="Lindqvist"/>
[[File:polarbrown-1.jpg|thumb|Polar/brown bear hybrid taxidermy specimen on display at Natural History Museum at Tring in Hertfordshire, England]]
More extensive genetic studies have refuted the idea that polar bears are directly descended from brown bears and found that the two species are separate [[Biology:Sister group|sister lineages]]. The genetic similarities between polar bears and some brown bears were found to be the result of interbreeding.<ref name="Hailer">{{cite journal |doi=10.1126/science.1216424 |pmid=22517859 |title=Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage |journal=Science |volume=336 |issue=6079 |pages=344–347 |year=2012 |last1=Hailer |first1=F. |last2=Kutschera |first2=V. E. |last3=Hallstrom |first3=B. M. |last4=Klassert |first4=D. |last5=Fain |first5=S. R. |last6=Leonard |first6=J. A. |last7=Arnason |first7=U. |last8=Janke |first8=A. |bibcode=2012Sci...336..344H|hdl=10261/58578 |s2cid=12671275|hdl-access=free }}</ref><ref name=Lan>{{cite journal|last1=Lan|first1=T.|last2=Leppälä|first2=K.|last3=Tomlin|first3=C.|last4=Talbot|first4=S. L.|last5=Sage|first5=G. K.|last6=Farley|first6=S. D.|last7=Shideler|first7=R. T.|last8=Bachmann|first8=L.|last9=Wiig|first9=Ø|last10=Albert|first10=V. A.|last11=Salojärvi|first11=J.|last12=Mailund|first12=T.|last13=Drautz-Moses|first13=D. I.|last14=Schuster|first14=S. C.|last15=Herrera-Estrella|first15=L.|last16=Lindqvist|first16=C.|year=2022|title=Insights into bear evolution from a Pleistocene polar bear genome|journal=Proceedings of the National Academy of Sciences|volume=119|issue=14|page=e2200016119|doi=10.1073/pnas.2200016119|doi-access=free |pmid=35666863|pmc=9214488|bibcode=2022PNAS..11900016L}}</ref> A 2012 study estimated the split between polar and brown bears as occurring around 600,000 years ago.<ref name="Hailer"/> A 2022 study estimated the divergence as occurring even earlier at over one million years ago.<ref name=Lan/> Glaciation events over hundreds of thousands of years led to both the origin of polar bears and their subsequent interactions and hybridizations with brown bears.<ref name=Hassanin>{{cite journal|last1=Hassanin|first1=A.|year=2015|title=The role of Pleistocene glaciations in shaping the evolution of polar and brown bears. Evidence from a critical review of mitochondrial and nuclear genome analyses|journal=Comptes Rendus Biologies|volume=338|issue=7|pages=494–501|doi=10.1016/j.crvi.2015.04.008|pmid=26026577|url=https://comptes-rendus.academie-sciences.fr/biologies/item/10.1016/j.crvi.2015.04.008.pdf}}</ref>

Studies in 2011 and 2012 concluded that [[Biology:Gene flow|gene flow]] went from brown bears to polar bears during hybridization.<ref name="Hailer"/><ref name=Edwards>{{cite journal|last1=Edwards|first1=C. J.|last2=Suchard|first2=M. A.|last3=Lemey|first3=P.|last4= Welch|first4=J. J.|last5=Barnes|first5=I.|last6=Fulton|first6=T. L.|last7=Barnett|first7=R.|last8=O'Connell|first8=T.|last9=Coxon|first9=P.|last10= Monaghan|first10=N.|last11=Valdiosera|first11=C. E.|last12=Lorenzen|first12=E. D.|last13=Willerslev|first13=E.|last14=Baryshnikov|first14=G. F.|last15=Rambaut|first15=A.|last16=Thomas|first16=M. G.|last17=Bradley|first17=D. G.|last18=Shapiro|first18=B.|year=2011|title=Ancient hybridization and an Irish origin for the modern polar bear matriline |journal=Current Biology|volume=21|issue=15|pages=1251–1258|doi=10.1016/j.cub.2011.05.058|pmid=21737280 |pmc=4677796 }}</ref> In particular, a 2011 study concluded that living polar bear populations derived their maternal lines from now-extinct Irish brown bears.<ref name=Edwards/> Later studies have clarified that gene flow went from polar to brown bears rather than the reverse.<ref name=Hassanin/><ref name=Cahill>{{cite journal|last1=Cahill|first1=J. A.|last2=Heintzman|first2=P. D.|last3=Harris|first3=K.|last4=Teasdale|first4=M. D.|last5=Kapp|first5=M. D.|last6=Soares|first6=A. E. R.|last7=Stirling|first7=I.|last8=Bradley|first8=D.|last9=Edward|first9=C. J.|last10=Graim|first10=K.|last11=Kisleika|first11=A. A.|last12=Malev|first12=A. V.|last13=Monaghan|first13=N.|last14=Green|first14=R. E.|last15=Shapiro|first15=B.|year=2018|title=Genomic evidence of widespread admixture from polar bears into brown bears during the last ice age|journal=Molecular Biology and Evolution|volume=35|issue=5|pages=1120–1129|doi=10.1093/molbev/msy018|pmid=29471451 |doi-access=free|hdl=10037/19512|hdl-access=free}}</ref><ref>{{cite journal|last1=Wang|first1=M-S|last2=Murray|first2=G. G. R.|last3=Mann|first3=D.|last4=Groves|first4=P.|last5=Vershinina|first5=A. O.|last6=Supple|first6=M. A.|last7=Kapp|first7=J. D.|last8=Corbett-Detig|first8=R.|last9=Crump|first9=S. E.|last10=Stirling|first10=I.|last11=Laidre|first11=K. L.|last12=Kunz|first12=M.|last13=Dalén|first13=L.|last14=Green|first14=R. E.|last15=Shapiro|first15=B.|year=2022|title=A polar bear paleogenome reveals extensive ancient gene flow from polar bears into brown bears|journal=Nature Ecology & Evolution|volume=6|issue=7|pages=936–944|doi=10.1038/s41559-022-01753-8|pmid=35711062 |bibcode=2022NatEE...6..936W |s2cid=249747066 }}</ref> Up to 9 percent of the genome of ABC bears was transferred from polar bears,<ref>{{cite journal|last1=Cahill|first1=J. A.|last2=Stirling|first2=I.|last3=Kistler|first3=L.|last4=Salamzade|first4=R.|last5=Ersmark|first5=E.|last6=Fulton|first6=T. L.|last7=Stiller|first7=M.|last8=Green|first8=R. E.|last9=Shapiro|first9=B.|year=2015|title=Genomic evidence of geographically widespread effect of gene flow from polar bears into brown bears|journal=Molecular Phylogenetics and Evolution|volume=24|issue=6|pages=1205–1217|doi=10.1111/mec.13038|pmid=25490862 |pmc=4409089 |bibcode=2015MolEc..24.1205C }}</ref> while Irish bears had up to 21.5 percent polar bear origin.<ref name=Cahill/> Mass hybridization between the two species appears to have stopped around 200,000 years ago. Modern hybrids are relatively rare in the wild.<ref name=Lan/>

Analysis of the [[Biology:Copy number variation|number of variations of gene copies]] in polar bears compared with brown bears and American black bears shows distinct adaptions. Polar bears have a less diverse array of [[Biology:Olfactory receptor|olfactory receptor]] genes, a result of there being fewer odours in their Arctic habitat. With its carnivorous, high-fat diet the species has fewer copies of the gene involved in making [[Biology:Amylase|amylase]], an enzyme that breaks down [[Chemistry:Starch|starch]], and more selection for genes for fatty acid breakdown and a more efficient [[Biology:Circulatory system|circulatory system]]. The polar bear's thicker coat is the result of more copies of genes involved in [[Biology:Keratin|keratin]]-creating proteins.<ref>{{cite journal|last1=Rink|first1=D. C.|last2=Specian|first2=N. K.|last3=Zhao|first3=S.|last4=Gibbons|first4=J. G.|year=2019|title=Polar bear evolution is marked by rapid changes in gene copy number in response to dietary shift|journal=Proceedings of the National Academy of Sciences|volume=116|issue=27|pages=13446–13451|doi=10.1073/pnas.1901093116 |doi-access=free |pmid=31209046 |pmc=6613075|bibcode=2019PNAS..11613446R }}</ref>

==Characteristics==
{{Multiple image
| align             = left
| direction         = vertical
| width             = 
| image1            = Description iconographique comparée du squelette et du système dentaire des mammifères récents et fossiles (Ursus maritimus skeleton).jpg
| caption1          = Polar bear skeleton
| image2            = Ursus maritimus 02 MWNH 420.JPG
| caption2          = Bear skull
}}
The polar bear is the largest living species of bear and land [[Biology:Carnivore|carnivore]], though some brown bear subspecies like the [[Biology:Kodiak bear|Kodiak bear]] can rival it in size.{{sfn|Derocher|2012|p=10}}{{sfn|Ellis|2009|p=74}} Males are generally {{convert|200|–|250|cm|ft|abbr=on}} long with a weight of {{convert|300|–|800|kg|abbr=on}}. Females are smaller at {{convert|180|–|200|cm|ft|abbr=on}} with a weight of {{convert|150|–|300|kg|abbr=on}}.<ref name="DeMaster1981">{{cite journal |last1=DeMaster |first1=Douglas P. |last2=Stirling |first2=Ian |date=8 May 1981 |title= ''Ursus maritimus''|jstor=3503828 |journal=Mammalian Species |pages=1–7 |doi=10.2307/3503828 |oclc=46381503 |issue=145 |doi-access=free }}</ref> [[Biology:Sexual dimorphism|Sexual dimorphism]] in the species is particularly high compared with most other mammals.{{sfn|Ellis|2009|p=75}} Male polar bears also have proportionally larger heads than females.{{sfn|Ellis|2009|p=80}} The weight of polar bears fluctuates during the year, as they can bulk up on fat and increase their mass by 50 percent.{{sfn|Derocher|2012|p=10}} A fattened, pregnant female can weigh as much as {{convert|500|kg|abbr=on}}.{{sfn|Stirling|2011|p=38}} Adults may stand {{convert|130|–|160|cm|ft|abbr=on}} tall at the shoulder. The tail is {{convert|76|–|126|mm|in|abbr=on}} long.<ref name="DeMaster1981"/> The largest polar bear on record, reportedly weighing {{convert|1002|kg|0|abbr=on}}, was a male shot at Kotzebue Sound in northwestern Alaska in 1960.<ref name="Wood">{{cite book |last=Wood |first=G. L. |year=1983 |title=The Guinness Book of Animal Records |page=[https://archive.org/details/guinnessbookofan00wood/page/27/mode/2up?q=polar+bear 28] |isbn=978-0-85112-235-9 |url=https://archive.org/details/guinnessbookofan00wood/page/27/mode/2up?q=polar+bear |publisher=Guinness Superlatives }}</ref>

Compared with the brown bear, this species has a more slender build, with a narrower, flatter and smaller skull, a longer neck, and a lower shoulder hump.{{sfn|Derocher|2012|p=10}}<ref name=Slater2010/> The snout profile is curved, resembling a "Roman nose".{{sfn|Derocher|2012|p=10}} They have 34–42 teeth including 12 incisors, 4 [[Biology:Canine tooth|canines]], 8–16 premolars and 10 molars. The teeth are adapted for a more carnivorous diet than that of the brown bear, having longer, sharper and more spaced out canines, and smaller, more pointed [[Biology:Cheek teeth|cheek teeth]] (premolars and molars).{{sfn|Ellis|2009|p=75}}{{sfn|Derocher|2012|p=17}}<ref name=Slater2010>{{cite journal|last1=Slater|first1=G. J.|last2=Figueirido|first2=B.|last3=Louis|first3=L.|last4=Yang|first4=P.|last5=Van Valkenburgh|first5=B.|year=2010|title=Biomechanical consequences of rapid evolution in the polar bear lineage|journal=PLOS ONE|volume=5|issue=11|page=e13870|doi=10.1371/journal.pone.0013870 |pmid=21079768 |pmc=2974639 |bibcode=2010PLoSO...513870S |doi-access=free }}</ref> The species has a large space or [[Medicine:Diastema|diastema]] between the canines and cheek teeth, which may allow it to better bite into prey.{{sfn|Derocher|2012|p=17}}<ref name=Figueirido>{{cite journal|last1=Figueirido|first1=B.|last2=Palmqvist|first2=P.|last3=Pérez-Claros|first3=J. A.|year=2009|title=Ecomorphological correlates of craniodental variation in bears and paleobiological implications for extinct taxa: an approach based on geometric morphometrics|journal=Journal of Zoology|volume=277|issue=1|pages=70–80|doi=10.1111/j.1469-7998.2008.00511.x}}</ref> Since it normally preys on animals much smaller than it, the polar bear does not have a particularly strong bite.<ref name=Figueirido/> Polar bears have large paws, with the front paws being broader than the back. The feet are hairier than in other bear species, providing warmth and friction when stepping on snow and sea ice.{{sfn|Derocher|2012|p=22}} The claws are small but sharp and hooked and are used both to snatch prey and climb onto ice.{{sfn|Derocher|2012|p=21}}{{sfn|Ellis|2009|p=79}}
[[File:Polar Bear AdF.jpg|thumb|right|Polar bear jumping on floating ice at Svalbard]]
The coat consists of dense underfur around {{convert|5|cm|abbr=on}} long and [[Biology:Guard hair|guard hair]]s around {{convert|15|cm|abbr=on}} long.<ref name="DeMaster1981"/> Males have long hairs on their forelegs, which is thought to signal their [[Biology:Fitness|fitness]] to females.<ref name="Dimorph">{{cite journal|last1=Derocher|first1=Andrew E.|first2=Magnus |last2=Andersen|first3=Øystein |last3=Wiig|year=2005|title=Sexual dimorphism of polar bears|jstor=4094434|journal=Journal of Mammalogy|volume=86|issue=5|pages=895–901|doi=10.1644/1545-1542(2005)86[895:SDOPB]2.0.CO;2|doi-access=free }}</ref> The outer surface of the hairs has a scaly appearance, and the guard hairs are hollow, which allows the animals to trap heat and float in the water.{{sfn|Derocher|2012|pp=7–8}} The transparent guard hairs [[Physics:Forward scatter|forward scatter]] [[Physics:Ultraviolet|ultraviolet]] light between the underfur and the skin, leading to a cycle of absorption and re-emission, keeping them warm.<ref name=Khattab/> The fur appears white due to the [[Physics:Backscatter|backscatter]] of [[Physics:Ray (optics)#Interaction with surfaces|incident light]] and the absence of pigment.<ref name=Khattab>{{cite journal|last1=Khattab|first1=M. Q.|last2=Tributsch|first2=H.|year=2015|title=Fibre-optical light scattering technology in polar bear hair: A re-evaluation and new results|journal=Journal of Advanced Biotechnology and Bioengineering|volume=3|issue=2|pages=38–51|doi=10.12970/2311-1755.2015.03.02.2}}</ref>{{sfn|Derocher|2012|p=7}} Polar bears gain a yellowish colouration as they are exposed more to the sun. This is reversed after they [[Biology:Moulting|moult]]. It can also be grayish or brownish.<ref name="DeMaster1981"/> Their light fur provides [[Biology:Camouflage|camouflage]] in their snowy environment. After emerging from the water, the bear can easily shake itself dry before freezing since the hairs are resistant to tangling when wet.{{sfn|Ellis|2009|pp=65, 72}} The skin, including the nose and lips, is black and absorbs heat.<ref name="DeMaster1981"/><ref name=Khattab/> Polar bears have a {{convert|5|–|10|cm|abbr=on}} thick layer of fat underneath the skin,<ref name="DeMaster1981"/> which provides both warmth and energy.{{sfn|Derocher|2012|p=12}} Polar bears maintain their core body temperature at about {{convert|36.9|C|F|0|abbr=on}}.<ref>{{cite journal|last=Best|first=R. C.|year=1982|title=Thermoregulation in resting and active polar bears|journal=Journal of Comparative Physiology A|volume=146|pages=63–73|doi=10.1007/BF00688718|s2cid=36351845 }}</ref> Overheating is countered by a layer of highly vascularized [[Biology:Striated muscle tissue|striated muscle tissue]] and finely controlled blood vessels. Bears also cool off by entering the water.<ref name=Khattab/><ref>{{cite journal|last1=Tributsch|first1=H.|last2=Goslowsky|first2=H.|last3=Küppers|first3=U.|last4=Wetzel|first4=H.|year=1990|title=Light collection and solar sensing through the polar bear pelt|journal=Solar Energy Materials|volume=21|issue=2–3|pages=219–236|doi=10.1016/0165-1633(90)90056-7}}</ref>

The eyes of a polar bear are close to the top of the head, which may allow them to stay out of the water when the animal is swimming at the surface. They are relatively small, which may be an adaption against blowing snow and snow blindness. Polar bears are [[Medicine:Dichromacy|dichromats]], and lack the [[Biology:Cone cell|cone cell]]s for seeing green. They have many [[Biology:Rod cell|rod cell]]s which allow them to see at night. The ears are small, allowing them to retain heat and not get frostbitten.{{sfn|Derocher|2012|pp=14, 16, 18–19}} They can hear best at frequencies of 11.2–22.5&nbsp;kHz, a wider frequency range than expected given that their prey mostly makes low-frequency sounds.<ref>{{cite journal|last1=Nachtigall|first1=P. E.|last2=Supin|first2=A. Y.|last3=Amundin|first3=M.|last4=Röken|first4=B.|last5=Møller|first5=T.|last6=Mooney|first6=T. A.|last7=Taylor|first7=K. A.|last8=Yuen|first8=M.|year=2007|title=Polar bear ''Ursus maritimus'' hearing measured with auditory evoked potentials|journal=Journal of Experimental Biology|volume=210|issue=7|pages=1116–1122|doi=10.1242/jeb.02734|pmid=17371910 |s2cid=18046149 |doi-access=free}}</ref> The [[Biology:Nasal concha|nasal concha]] creates a large surface area, so more warm air can move through the nasal passages.{{sfn|Derocher|2012|p=14}} Their olfactory system is also large and adapted for smelling prey over vast distances.<ref>{{cite journal|last1=Green|first1=P. A.|last2=Van Valkenburgh|first2=B.|last3=Pang|first3=B.|last4=Bird|first4=B.|last5=Rowe|first5=T.|last6=Curtis|first6=A.|year=2012|title=Respiratory and olfactory turbinal size in canid and arctoid carnivorans|journal=Journal of Anatomy|volume=221|issue=6|pages=609–621|doi=10.1111/j.1469-7580.2012.01570.x|pmid=23035637 |pmc=3512284 }}</ref> The animal has [[Biology:Reniculate kidney|reniculate kidney]]s which filter out the salt in their food.{{sfn|Derocher|2012|p=26}}

==Distribution and habitat==
[[File:Polar bear subpopulation map.svg|thumb|right|Map of 19 polar bear subpopulations. The Queen Elizabeth Islands (QE) subpopulation is not universally accepted.<ref name=statusreport/>]]
Polar bears inhabit the Arctic and adjacent areas. Their range includes Greenland, Canada, Alaska, Russia and the Svalbard Archipelago of Norway.<ref name="DeMaster1981"/>{{sfn|Ellis|2009|pp=73, 140}}{{sfn|Derocher|2012|p=3}} Polar bears have been recorded {{convert|25|km|abbr=on}} from the [[Earth:North Pole|North Pole]].<ref>{{cite journal|last1=van Meurs|first1=R.|last2=Splettstoesser|first2=J. F.|year=1993|title=Letter to the editor: farthest north polar bear|journal=Arctic|volume=56|issue=3|page=309|doi=10.14430/arctic626|doi-access=free}}</ref> The southern limits of their range include James Bay and Newfoundland and Labrador in Canada and St. Matthew Island and the Pribilof Islands of Alaska.<ref name="DeMaster1981"/> They are not permanent residents of Iceland but have been recorded visiting there if they can reach it via sea ice.{{sfn|Ellis|2009|pp=122–124}} Due to minimal human encroachment on the bears' remote habitat, they can still be found in much of their original range, more so than any other large land carnivore.<ref name="derocher2004">{{cite journal|last1=Derocher|first1=Andrew E.|last2=Lunn|first2=Nicholas J.|last3=Stirling|first3=Ian|year=2004|title=Polar bears in a warming climate|journal=Integrative and Comparative Biology|volume=44|issue=2|pages=163–176|doi=10.1093/icb/44.2.163|pmid=21680496|doi-access=free}}</ref>

Polar bears have been divided into at least 18 subpopulations labelled East Greenland (ES), Barents Sea (BS), Kara Sea (KS), Laptev Sea (LVS), Chukchi Sea (CS), northern and southern Beaufort Sea (SBS and NBS), Viscount Melville (VM), M'Clintock Channel (MC), Gulf of Boothia (GB), Lancaster Sound (LS), Norwegian Bay (NB), Kane Basin (KB), Baffin Bay (BB), Davis Strait (DS), Foxe Basin (FB) and the western and southern Hudson Bay (WHB and SHB) populations.<ref name=Peacock2015>{{cite journal|last1=Peacock|first1=E.|last2=Sonsthagen|first2=S. A.|last3=Obbard|first3=M. E.|last4=Boltunov|first4=A.|last5=Regehr|first5=E. V.|last6=Ovsyanikov|first6=N.|last7=Aars|first7=J.|last8=Atkinson|first8=S. N.|last9=Sage|first9=G. K.|last10=Hope|first10=A. G.|last11=Zeyl|first11=E.|last12=Bachmann|first12=L.|last13=Ehrich|first13=D.|last14=Scribner|first14=K. T.|last15=Amstrup|first15=S. C.|last16=Belikov|first16=S.|last17=Born|first17=E. W.|last18=Derocher|first18=A. E.|last19=Stirling|first19=I.|last20=Taylor|first20=M. K.|last21=Wiig|first21=Ø|last22=Paetkau|first22=D.|last23=Talbot|first23=S. L.|year=2015|title=Implications of the circumpolar genetic structure of polar bears for their conservation in a rapidly warming Arctic|journal=PLOS ONE|volume=10|issue=1|page=e112021|doi=10.1371/journal.pone.0112021|pmid=25562525|pmc=4285400|bibcode=2015PLoSO..10k2021P|doi-access=free}}</ref><ref name=statusreport/> Bears in and around the Queen Elizabeth Islands have been proposed as a subpopulation but this is not universally accepted.<ref name=statusreport/> A 2022 study has suggested that the bears in southeast Greenland should be considered a different subpopulation based on their geographic isolation and genetics.<ref>{{cite journal|last1=Laidre|first1=K. L.|last2=Supple|first2=M. A.|last3=Born|first3=E. W.|last4=Regehr|first4=E. V.|last5=Wiig|first5=Ø|last6=Ugarte|first6=F.|last7=Aars|first7=J.|last8=Dietz|first8=R.|last9=Sonne|first9=C.|last10=Hegelund|first10=P.|last11=Isaksen|first11=C.|last12=Akse|first12=G. B.|last13=Cohen|first13=B.|last14=Stern|first14=H. L.|last15=Moon|first15=T.|last16=Vollmers|first16=C.|last17=Corbett-Detig|first17=R.|last18=Paetkau|first18=D.|last19=Shapiro|first19=B.|year=2022|title=Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st-century sea-ice conditions|journal=Science|volume=376|issue=6599|pages=1333–1338|doi=10.1126/science.abk2793|pmid=35709290 |bibcode=2022Sci...376.1333L |s2cid=249746650 |url=https://repository.library.noaa.gov/view/noaa/53746 }}</ref> Polar bear populations can also be divided into four [[Biology:Gene cluster|gene cluster]]s: Southern Canadian, [[Place:Arctic Archipelago|Canadian Archipelago]], Western Basin (northwestern Canada west to the [[Place:Russian Far East|Russian Far East]]) and Eastern Basin (Greenland east to Siberia).<ref name=Peacock2015/>

The polar bear is dependent enough on the ocean to be considered a [[Biology:Marine mammal|marine mammal]].<ref name=":0"/>{{sfn|Stirling|2011|p=XIII}} It is pagophilic and mainly inhabits annual [[Earth:Sea ice|sea ice]] covering [[Earth:Continental shelf|continental shelves]] and between islands of archipelagos. These areas, known as the "Arctic Ring of Life", have high [[Earth:Productivity (ecology)|biological productivity]].<ref name="derocher2004"/>{{sfn|Stirling|2011|pp=9–10}} The species tends to frequent areas where sea ice meets water, such as [[Earth:Polynya|polynya]]s and leads, to hunt the [[Biology:Pinniped|seals]] that make up most of its diet.<ref>{{cite journal |last1=Stirling |first1=Ian |year=1997 |title=The importance of polynyas, ice edges, and leads to marine mammals and birds |volume=10 |issue=1–4 |pages=9–21 |doi=10.1016/S0924-7963(96)00054-1 |journal=Journal of Marine Systems|bibcode=1997JMS....10....9S }}</ref> Polar bears travel in response to changes in ice cover throughout the year. They are forced onto land in summer when the sea ice disappears.{{sfn|Stirling|2011|p=9}} Terrestrial habitats used by polar bears include forests, mountains, rocky areas, lakeshores and creeks.{{sfn|Derocher|2012|pp=67–68}} In the Chukchi and Beaufort seas, where the sea ice breaks off and floats north during the summer, polar bears generally stay on the ice, though a large portion of the population (15&ndash;40%) has been observed spending all summer on land since the 1980s.<ref>{{cite journal |last1=Rode |first1=Karyn D. |last2=Douglas |first2=D. C. |last3=Atwood |first3=T. C. |last4=Durner |first4=G. M. |last5=Wilson |first5=R. R. |last6=Pagano |first6=A. M. |date=December 2022 |journal=Global Ecology and Conservation |volume=40 |title=Observed and forecasted changes in land use by polar bears in the Beaufort and Chukchi Seas, 1985–2040 |page=e02319|doi=10.1016/j.gecco.2022.e02319 |doi-access=free }}</ref> Some areas have thick [[Earth:Sea ice#Old sea ice|multiyear]] ice that does not completely melt and the bears can stay on all year,<ref name=Vongraven>{{cite journal|last1=Vongraven|first1=D.|last2=Aars|first2=J.|last3=Amstrup|first3=S.|last4=Atkinson|first4=S. N.|last5=Belikov|first5=S.|last6=Born|first6=E. W.|last7=DeBruyn|first7=T. D.|last8=Derocher|first8=A. E.|last9=Durner|first9=G.|last10=Gill|first10=M.|last11=Lunn|first11=N.|last12=Obbard|first12=M. E.|last13=Omelak|first13=J.|last14=Ovsyanikov|first14=N.|last15=Peacock|first15=E.|last16=Richardson|first16=E.|last17=Sahanatien|first17=V.|last18=Stirling|first18=I.|last19=Wiig|first19=Ø|year=2012|title=A circumpolar monitoring framework for polar bears|journal=Ursus: Monograph Series Number 5|volume=23|pages=1–66|doi=10.2192/URSUS-D-11-00026.1|s2cid=67812839}}</ref>{{sfn|Stirling|2011|p=4}} though this type of ice has fewer seals and allows for less productivity in the water.{{sfn|Stirling|2011|p=4}}

==Behaviour and ecology==
Polar bears may travel areas as small as {{cvt|3500|km2|abbr=on}} to as large as {{cvt|38000|km2|abbr=on}} in a year, while drifting ice allows them to move further.<ref>{{cite journal|last1=Auger-Méthé|first1=M.|last2=Lewis|first2=M. A.|last3=Derocher|first3=A. E.|year=2016|title=Home ranges in moving habitats: polar bears and sea ice|journal=Ecography|volume=32|issue=1|pages=26–35|doi=10.1111/ecog.01260|bibcode=2016Ecogr..39...26A }}</ref> Depending on ice conditions, a bear can travel an average of {{convert|12|km|mi|abbr=on}} per day.<ref>{{cite journal|last1=Ferguson|first1=S. H.|last2=Taylor|first2=M. K.|last3=Born|first3=E. W.|last4=Rosing-Asvid|first4=A.|last5=Messier|first5=F.|year=2001|title=Activity and movement patterns of polar bears inhabiting consolidated versus active pack ice|journal=Arctic|volume=54|issue=1|pages=49–54|doi=10.14430/arctic763|doi-access=free}}</ref> These movements are powered by their energy-rich diet.{{sfn|Derocher|2012|p=12}} Polar bears move by walking and galloping and do not trot.<ref>{{cite journal|last1=Gasc|first1=J-P|last2=Abourachid|first2=A|year=1997|title=Kinematic analysis of the locomotion of the polar bear (''Ursus maritimus'', Phipps, 1774) in natural and experimental conditions|journal=Netherlands Journal of Zoology|volume=48|issue=2|pages=145–167|doi=10.1163/156854298X00156}}</ref> Walking bears tilt their front paws towards each other.{{sfn|Derocher|2012|p=21}} They can run at estimated speeds of up to {{convert|40|km/h|abbr=on}}<ref name="Brook"/> but typically move at around {{convert|5.5|km/h|abbr=on}}.{{sfn|Stirling|2011|p=140}} Polar bears are also capable swimmers and can swim at up to {{convert|6|km/h|abbr=on}}.{{sfn|Ellis|2009|p=88}} One study found they can swim for an average of 3.4 days at a time and travel an average of {{convert|154.2|km|mi|abbr=on}}.<ref>{{cite journal|last1=Pagano|first1=A. M.|last2=Durner|first2=G M.|last3=Amstrup|first3=S. C.|last4=Simac|first4=K. S.|last5=York|first5=G. S.|year=2012|title=Long-distance swimming by polar bears (''Ursus maritimus'') of the southern Beaufort Sea during years of extensive open water|journal=Canadian Journal of Zoology|volume=90|issue=5|pages=663–676|doi=10.1139/Z2012-033|url=https://zenodo.org/record/1235909 }}</ref> They can dive for as long as three minutes.<ref name="Stirling & van Meurs 2015">{{cite journal|last1=Stirling|first1=Ian|last2=van Meurs|first2=Rinie|title=Longest recorded underwater dive by a polar bear|journal=Polar Biology|volume=38|issue=8|date=2015|pages=1301–1304|doi=10.1007/s00300-015-1684-1|bibcode=2015PoBio..38.1301S |s2cid=6385494}}</ref>  When swimming, the broad front paws do the paddling, while the hind legs play a role in steering and diving.<ref name="DeMaster1981"/>{{sfn|Derocher|2012|p=21}}
[[File:Mother cubs.JPG|thumb|right|Mother bear and cubs sleeping]]
Most polar bears are active year-round. [[Biology:Hibernation|Hibernation]] occurs only among pregnant females.{{sfn|Derocher|2012|p=28}} Non-hibernating bears typically have a normal [[Biology:Circadian rhythm|24-hour cycle]] even during days of [[Earth:Polar night|all darkness]] or [[Astronomy:Midnight sun|all sunlight]], though cycles less than a day are more common during the former.<ref>{{cite journal|last1=Ware|first1=J. V.|last2=Rode|first2=K. D.|last3=Robbins|first3=C. T.|last4=Leise|first4=T.|last5=Weil|first5=C. R.|last6=Jansen|first6=H. T.|year=2020|title=The clock keeps ticking: circadian rhythms of free-ranging polar bears|journal=Journal of Biological Rhythms|volume=35|issue=2|pages=180–194 |doi=10.1177/0748730419900877|pmid=31975640 |s2cid=210882454 |doi-access=free}}</ref> The species is generally [[Biology:Diurnality|diurnal]], being most active early in the day.<ref>{{cite journal|last1=Stirling|first1=I.|year=1974|title=Midsummer observations on the behavior of wild polar bears (''Ursus maritimus'')|journal=Canadian Journal of Zoology|volume=52|issue=9|pages=1191–1198|doi=10.1139/z74-157}}</ref> Polar bears sleep close to eight hours a day on average.{{sfn|Stirling|2011|p=141}} They will sleep in various positions, including curled up, sitting up, lying on one side, on the back with limbs spread, or on the belly with the rump elevated.{{sfn|Ellis|2009|p=79}}{{sfn|Stirling|2011|p=140}} On sea ice, polar bears snooze at [[Earth:Pressure ridge (ice)|pressure ridges]] where they dig on the sheltered side and lie down. After a snowstorm, a bear may rest under the snow for hours or days. On land, the bears may dig a resting spot on gravel or sand beaches.{{sfn|Stirling|2011|pp=140–141}} They will also sleep on rocky outcrops.{{sfn|Derocher|2012|p=68}} In mountainous areas on the coast, mothers and subadults will sleep on slopes where they can better spot another bear coming.{{sfn|Stirling|2011|p=141}} Adult males are less at risk from other bears and can sleep nearly anywhere.{{sfn|Derocher|2012|p=68}}

===Social life===
[[File:Play fight of polar bears edit 1.ogv|thumb|right|Young bears play-fighting]]
Polar bears are typically solitary, aside from mothers with cubs and mating pairs.{{sfn|Stirling|2011|p=105}} On land, they are found closer together and gather around food resources. Adult males, in particular, are more tolerant of each other in land environments and outside the breeding season.<ref name=Derocher1990>{{cite journal|last1=Derocher|first1=A. E.|last2=Stirling|first2=I.|year=1990|title=Observations of aggregating behaviour in adult male polar bears (''Ursus maritimus'')|journal=Canadian Journal of Zoology|volume=68|issue=7|pages=1390–1394|doi=10.1139/z90-207}}</ref><ref name=Ferguson1997>{{cite journal|last1=Ferguson|first1=S. H.|last2=Taylor|first2=M. K.|last3=Messier|first3=F.|year=1997|title=Space use by polar bears in and around Auyuittuq National Park, Northwest Territories, during the ice-free period|journal=Canadian Journal of Zoology|volume=75|issue=10|pages=1585–1594|doi=10.1139/z97-785}}</ref> They have been recorded forming stable "alliances", travelling, resting and playing together. A [[Dominance hierarchy|dominant hierarchy]] exists among polar bears with the largest mature males ranking at the top. Adult females outrank subadults and adolescents and younger males outrank females of the same age. In addition, cubs with their mothers outrank those on their own.<ref name=Ovsyanikov2005>{{cite journal|last=Ovsyanikov|first=N. G.|year=2005|title=Behavior of polar bears in coastal congregations|journal=Zoologicheskiĭ Zhurnal|volume=84|issue=1|pages=94–103|url=https://www.arlis.org/docs/vol1/E/Walrus/Russian/Ovsyanikov.2005.BehaviorPolarBearCoastalCongreg.ZoolZhurnal.pdf}}</ref> Females with dependent offspring tend to stay away from males,<ref name=Ferguson1997/> but are sometimes associated with other female–offspring units, creating "composite families".<ref name=Ovsyanikov2005/>

Polar bears are generally quiet but can produce various sounds.{{sfn|Derocher|2012|p=30}} Chuffing, a soft pulsing call, is made by mother bears presumably to keep in contact with their young.<ref name=Wemmer1976/> During the breeding season, adult males will chuff at potential mates.{{sfn|Derocher|2012|p=31}} Unlike other animals where chuffing is passed through the nostrils, in polar bears it is emitted through a partially open mouth.<ref name=Wemmer1976>{{cite journal|last1=Wemmer|first1=C.|last2=Von Ebers|first2=M.|last3=Scow|first3=K.|year=1976|title=An analysis of the chuffing vocalization in the polar bear (''Ursus maritimus'')|journal=Journal of Zoology|volume=180|issue=3|pages=425–439|doi=10.1111/j.1469-7998.1976.tb04686.x}}</ref> Cubs will cry for attention and produce humming noises while nursing.<ref>{{cite journal|last1=Derocher|first1=A. E.|last2=Van Parijs|first2=S. M.|last3=Wiig|first3=Ø|year=2010|title=Nursing vocalization of a polar bear cub|journal=Ursus|volume=21|issue=2|pages=189–191|doi=10.2192/09SC025.1|s2cid=55599722}}</ref> Teeth chops, jaw pops, blows, huffs, moans, [[Physics:Growling|growls]] and roars are heard in more hostile encounters.{{sfn|Derocher|2012|p=31}} A polar bear visually communicates with its eyes, ears, nose and lips.<ref name=Ovsyanikov2005/> Chemical communication can also be important: bears secrete their scent from their foot pads into their tracks, allowing individuals to keep track of one another.<ref>{{cite journal |author1=Owen, M. A. |author2=Swaisgood, R. R. |author3=Slocomb, C. |author4=Amstrup, S. C. |author5=Durner, G. M. |author6=Simac, K. |author7=Pessier, A. P. |year=2014 |title=An experimental investigation of chemical communication in the polar bear |journal=Journal of Zoology |volume=295 |issue=1 |pages=36–43 |doi=10.1111/jzo.12181}}</ref>

===Diet and hunting===
The polar bear is a hypercarnivore,<ref name=Sacco2004/> and the most carnivorous species of bear.<ref name=Slater2010/> It is an [[Biology:Apex predator|apex predator]] of the Arctic,{{sfn|Stirling|2011|p=155}} preying on ice-living seals and consuming their energy-rich blubber.{{sfn|Derocher|2012|p=69}} The most commonly taken species is the ringed seal, but they also prey on [[Biology:Bearded seal|bearded seal]]s and harp seals.<ref name="DeMaster1981"/> Ringed seals are ideal prey as they are abundant and small enough to be overpowered by even small bears.{{sfn|Stirling|2011|pp=155–156}} Bearded seal adults are larger and are more likely to break free from an attacking bear, hence adult male bears are more successful in hunting them. Less common prey are [[Biology:Hooded seal|hooded seal]]s, [[Biology:Spotted seal|spotted seal]]s, ribbon seals and the more temperate-living harbour seals.{{sfn|Derocher|2012|pp=73, 76–77}} Polar bears, mostly adult males, will occasionally hunt [[Biology:Walrus|walrus]]es, both on land and ice, though they mainly target the young, as adults are too large and formidable, with their thick skin and long tusks.{{sfn|Stirling|2011|p=161}}

[[File:Polar bear (Ursus maritimus) with its prey.jpg|thumb|right|Bear feeding on a bearded seal]]
Besides seals, bears will prey on [[Biology:Cetacea|cetacea]]n species such as [[Biology:Beluga whale|beluga whale]]s and [[Biology:Narwhal|narwhal]]s, as well as [[Biology:Reindeer|reindeer]], birds and their eggs, fish and [[Biology:Marine invertebrates|marine invertebrates]].{{sfn|Derocher|2012|pp=80–88}} They rarely eat plant material as their digestive system is too specialized for animal matter,<ref>{{cite journal |last1=Ramsay |first1=M. A. |last2=Hobson |first2=K. A. |date=May 1991 |title=Polar bears make little use of terrestrial food webs: evidence from stable-carbon isotope analysis |volume=86 |issue=4 |pages=598–600 |doi=10.1007/BF00318328 |pmid=28313343 |journal=Oecologia|bibcode=1991Oecol..86..598R |s2cid=32221744 }}</ref> though they have been recorded eating berries, moss, grass and [[Biology:Seaweed|seaweed]].{{sfn|Derocher|2012|pp=88–89}} In their southern range, especially near Hudson Bay and James Bay, polar bears endure all summer without sea ice to hunt from and must subsist more on terrestrial foods.<ref name="ReferenceB">{{cite journal |last1=Russell |first1=Richard H. |title=The food habits of polar bears of James Bay and Southwest Hudson Bay in summer and autumn |journal=Arctic |date=1975|volume=28 |issue=2 |pages=117–129 |doi=10.14430/arctic2823 |doi-access=free }}</ref> Fat reserves allow polar bears to survive for months without eating.{{sfn|Ellis|2009|p=89}} [[Biology:Cannibalism|Cannibalism]] is known to occur in the species.<ref name=Taylor1985/>

Polar bears hunt their prey in several different ways. When a bear spots a seal [[Biology:Hauling-out|hauling out]] on the sea ice, it slowly stalks it with the head and neck lowered, possibly to make its dark nose and eyes less noticeable. As it gets closer, the bear crouches more and eventually charges at a high speed, attempting to catch the seal before it can escape into its ice hole. Some stalking bears need to move through water; traversing through water cavities in the ice when approaching the seal or swimming towards a seal on an ice floe. The polar bear can stay underwater with its nose exposed. When it gets close enough, the animal lunges from the water to attack.{{sfn|Stirling|2011|pp=170–171}}

During a limited time in spring, polar bears will search for ringed seal pups in their birth lairs underneath the ice. Once a bear catches the scent of a hiding pup and pinpoints its location, it approaches the den quietly to not alert it. It uses its front feet to smash through the ice and then pokes its head in to catch the pup before it can escape. A ringed seal's lair can be more than {{convert|1|m|ft|abbr=on}} below the surface of the ice and thus more massive bears are better equipped for breaking in. Some bears may simply stay still near a breathing hole or other spot near the water and wait for prey to come by.{{sfn|Derocher|2012|pp=127–129, 131}} This can last hours and when a seal surfaces the bear will try to pull it out with its paws and claws.{{sfn|Ellis|2009|p=91}} This tactic is the primary hunting method from winter to early spring.<ref name="DeMaster1981"/>
[[File:Polar Bear ANWR 10.jpg|thumb|left|Bear with whale carcass]]
Bears hunt walrus groups by provoking them into stampeding and then look for young that have been crushed or separated from their mothers during the turmoil.{{sfn|Stirling|2011|p=161}} There are reports of bears trying to kill or injure walruses by throwing rocks and pieces of ice on them.<ref>{{cite journal|last1=Stirling|first1=I.|last2=Laidre|first2=K. L.|last3=Born|first3=E. W.|year=2021|title=Do wild polar bears (''Ursus maritimus'') use tools when hunting walruses (''Odobenus rosmarus'')?|journal=Arctic|volume=74|issue=2|pages=175–187|doi=10.14430/arctic72532|s2cid=236227117|doi-access=free}}</ref> Belugas and narwhals are vulnerable to bear attacks when they are stranded in shallow water or stuck in isolated breathing holes in the ice.{{sfn|Derocher|2012|pp=80–83}} When stalking reindeer, polar bears will hide in vegetation before an ambush.<ref name="Brook">{{cite journal |last1=Brook |first1=R. K. |last2=Richardson |first2=E. S. |year=2002 |title=Observations of polar bear predatory behaviour toward caribou |journal=Arctic |volume=55 |issue=2 |pages=193–196 |doi=10.14430/arctic703|doi-access=free }}</ref> On some occasions, bears may try to catch prey in open water, swimming underneath a seal or aquatic bird. Seals in particular, however, are more agile than bears in the water.{{sfn|Derocher|2012|pp=84–85, 132}} Polar bears rely on raw power when trying to kill their prey, and will employ bites and paw swipes.<ref name=Sacco2004>{{cite journal|last1=Sacco|first1=T.|last2=Van Valkenburgh|first2=B.|year=2004|title=Ecomorphological indicators of feeding behaviour in the bears (Carnivora: Ursidae)|journal=Journal of Zoology|volume=263|issue=1|pages=41–54|doi=10.1017/S0952836904004856}}</ref> They have the strength to pull a mid-sized seal out of the water or haul a beluga carcass for quite some distance.{{sfn|Ellis|2009|p=112}} Polar bears only occasionally [[Biology:Hoarding (animal behavior)|store]] food for later—burying it under snow—and only in the short term.<ref>{{cite journal|last1=Stirling|first1=I.|last2=Laidre|first2=K. L.|last3=Derocher|first3=A. E.|last4=Van Meurs|first4=R.|year=2020|title=The ecological and behavioral significance of short-term food caching in polar bears (''Ursus maritimus'')|journal=Arctic Science|volume=6|issue=1|pages=41–52|doi=10.1139/as-2019-0008|s2cid=209575444}}</ref>

[[Biology:Arctic fox|Arctic fox]]es routinely follow polar bears and scavenge scraps from their kills. The bears usually tolerate them but will charge a fox that gets too close when they are feeding. Polar bears themselves will scavenge. Subadult bears will eat remains left behind by others. Females with cubs often abandon a carcass when they see an adult male approaching, though are less likely to if they have not eaten in a long time.{{sfn|Stirling|2011|pp=191–193}} Whale carcasses are a valuable food source, particularly on land and after the sea ice melts, and attract several bears.<ref name=Derocher1990/> In one area in northeastern Alaska, polar bears have been recorded competing with [[Biology:Grizzly bear|grizzly bear]]s for whale carcasses. Despite their smaller size, grizzlies are more aggressive and polar bears are likely to yield to them in confrontations.<ref>{{cite journal|last1=Miller|first1=S.|last2=Wilder|first2=J.|last3=Wilson|first3=R. R.|year=2015|title=Polar bear–grizzly bear interactions during the autumn open-water period in Alaska|journal=Journal of Mammalogy|volume=96|issue=6|pages=1317–1325|doi=10.1093/jmammal/gyv140|doi-access=free}}</ref> Polar bears will also scavenge at garbage dumps during ice-free periods.<ref>{{cite journal|last1=Lunn|first1=N. J.|last2=Stirling|first2=I.|year=1985|title=The significance of supplemental food to polar bears during the ice-free period of Hudson Bay|journal=Canadian Journal of Zoology|volume=63|issue=10|pages=2291–2297|doi=10.1139/z85-340}}</ref>

===Reproduction and development===
[[File:Встреча 2.jpg|thumb|right|Courting male approaching female]]
Polar bear mating takes place on the sea ice and during spring, mostly between March and May.<ref name="DeMaster1981"/><ref name=Ramsay1986>{{cite journal|last1=Ramsay|first1=M. A.|last2=Stirling|first2=I.|year=1986|title=On the mating system of polar bears|journal=Canadian Journal of Zoology|volume=64|issue=10|pages=2142–2151|doi=10.1139/z86-329}}</ref><ref name=Derocher2010/>{{sfn|Stirling|2011|p=105}} Males search for females in estrus and often travel in twisting paths which reduces the chances of them encountering other males while still allowing them to find females. The movements of females remain linear and they travel more widely.<ref>{{cite journal|last1=Laidre|first1=K. L.|last2=Born|first2=E. W.|last3=Gurarie|first3=E.|last4=Wiig|first4=Ø|last5=Dietz|first5=R.|last6=Stern|first6=H.|year=2013|title=Females roam while males patrol: divergence in breeding season movements of pack-ice polar bears (''Ursus maritimus'')|journal=Proceedings of the Royal Society B: Biological Sciences|volume=280|issue=1752 |page=20122371|doi=10.1098/rspb.2012.2371|pmid=23222446 |pmc=3574305 }}</ref> The mating system can be labelled as female-defence [[Biology:Polygyny in animals|polygyny]], serial monogamy or [[Social:Promiscuity#Other animals|promiscuity]].<ref name=Derocher2010>{{cite journal|last1=Derocher|first1=A. E.|last2=Anderson|first2=M.|last3=Wiig|first3=Ø|last4=Aars|first4=J.|year=2010|title=Sexual dimorphism and the mating ecology of polar bears (Ursus maritimus) at Svalbard (''Ursus maritimus'') at Svalbard|journal=Behavioral Ecology and Sociobiology|volume=64|issue=6|pages=939–946|doi=10.1007/s00265-010-0909-0|s2cid=36614970 }}</ref><ref name=Zey2009/>

Upon finding a female, a male will try to isolate and guard her. Courtship can be somewhat aggressive, and a male will pursue a female if she tries to run away. It can take days for the male to mate with the female which [[Biology:Induced ovulation (animals)|induces ovulation]]. After their first copulation, the couple bond. Undisturbed polar bear pairings typically last around two weeks during which they will sleep together and mate multiple times.{{sfn|Derocher|2012|pp=141, 145–147}} Competition for mates can be intense and this has led to [[Biology:Sexual selection|sexual selection]] for bigger males. Polar bear males often have scars from fighting.<ref name=Ramsay1986/><ref name=Derocher2010/> A male and female that have already bonded will flee together when another male arrives.{{sfn|Derocher|2012|pp=145–147}} A female mates with multiple males in a season and a single litter can have more than one father.<ref name=Zey2009>{{cite journal|last1=Zeyl|first1=E.|last2=Aars|first2=J.|last3=Ehrich|first3=D.|last4=Bachmann|first4=L.|last5=Wiig|first5=Ø|year=2009|title=The mating system of polar bears: a genetic approach|journal=Canadian Journal of Zoology|volume=87|issue=12|pages=1195–1209|doi=10.1139/Z09-107}}</ref> 
[[File:Polar bear cubs in the snow.jpg|thumb|left|Polar bear cubs]]
When the mating season ends, the female will build up more fat reserves to sustain both herself and her young. Sometime between August and October, the female constructs and enters a [[Biology:Maternity den|maternity den]] for winter. Depending on the area, maternity dens can be found in sea ice just off the coastline or further inland and may be dug underneath snow, earth or a combination of both.{{sfn|Stirling|2011|pp=112, 115, 120}} The inside of these shelters can be around {{convert|1.5|m|ft|abbr=on}} wide with a ceiling height of {{convert|1.2|m|ft|abbr=on}} while the entrance may be {{convert|2.1|m|ft|abbr=on}} long and {{convert|1.2|m|ft|abbr=on}} wide. The temperature of a den can be much higher than the outside.{{sfn|Ellis|2009|p=85}} Females hibernate and give birth to their cubs in the dens.{{sfn|Derocher|2012|pp=28, 155}} Hibernating bears [[Philosophy:Fasting|fast]] and internally recycle bodily waste. Polar bears experience delayed implantation and the fertilized embryo does not start development until the fall, between mid-September and mid-October.{{sfn|Stirling|2011|p=124}} With delayed implantation, gestation in the species lasts seven to nine months but actual pregnancy is only two months.{{sfn|Derocher|2012|p=171}}

Mother polar bears typically give birth to two cubs per litter. As with other bear species, newborn polar bears are tiny and [[Biology:Precociality and altriciality|altricial]].{{sfn|Stirling|2011|pp=124–125, 131}} The newborns have woolly hair and pink skin, with a weight of around {{convert|600|g|abbr=on}}.<ref name="DeMaster1981"/>{{sfn|Derocher|2012|p=10}} Their eyes remain closed for a month.{{sfn|Ellis|2009|p=84}} The mother's fatty milk fuels their growth, and the cubs are kept warm both by the mother's body heat and the den. The mother emerges from the den between late February and early April, and her cubs are well-developed and capable of walking with her.{{sfn|Stirling|2011|pp=126–127}} At this time they weigh {{convert|10|–|15|kg}}.<ref name="DeMaster1981"/> A polar bear family stays near the den for roughly two weeks; during this time the cubs will move and play around while the mother mostly rests. They eventually head out on the sea ice.{{sfn|Stirling|2011|p=128}}
[[File:Cub polar bear is nursing 2.OGG|thumb|right|Mother nursing her young]]
Cubs under a year old stay close to their mother. When she hunts, they stay still and watch until she calls them back.{{sfn|Derocher|2012|pp=173, 184}} Observing and imitating the mother helps the cubs hone their hunting skills.{{sfn|Stirling|2011|p=186}} After their first year they become more independent and explore. At around two years old, they are capable of hunting on their own.{{sfn|Derocher|2012|p=184}} The young suckle their mother as she is lying on her side or sitting on her rump.{{sfn|Stirling|2011|p=128}} A lactating female cannot conceive and give birth,{{sfn|Derocher|2012|p=181}} and cubs are weaned between two and two-and-a-half years.<ref name="DeMaster1981"/> She may simply leave her weaned young or they may be chased away by a courting male.{{sfn|Derocher|2012|p=184}} Polar bears reach sexual maturity at around four years for females and six years for males.{{sfn|Stirling|2011|pp=128–129}} Females reach their adult size at 4 or 5 years of age while males are fully grown at twice that age.{{sfn|Derocher|2012|p=185}}

===Mortality===
Polar bears can live up to 30 years.<ref name="DeMaster1981"/> The bear's long lifespan and ability to consistently produce young offsets cub deaths in a population. Some cubs die in the dens or the womb if the female is not in good condition. Nevertheless, the female has a chance to produce a surviving litter the next spring if she can eat better in the coming year. Cubs will eventually starve if their mothers cannot kill enough prey.{{sfn|Stirling|2011|pp=204–207}} Cubs also face threats from wolves<ref>{{cite journal|last1=Richardson|first1=E. S.|last2=Andriashek|first2=D.|year=2006|title=Wolf (''Canis lupus'') predation of a polar bear (''Ursus maritimus'') cub on the sea ice off northwestern Banks Island, Northwest Territories, Canada|journal=Arctic|volume=59|issue=3|pages=322–324|doi=10.14430/arctic318|doi-access=free}}</ref> and adult male bears. Males [[Biology:Infanticide (zoology)|kill cubs]] to bring their mother back into estrus but also kill young outside the breeding season for food.<ref name=Taylor1985>{{cite journal|last1=Taylor|first1=M.|last2=Larsen|first2=T.|last3=Schweinsburg|first3=R. E.|year=1985|title=Observations of intraspecific aggression and cannibalism in polar bears (''Ursus maritimus'')|journal=Arctic|volume=38|issue=4|pages=303–309|doi=10.14430/arctic2149|doi-access=free}}</ref> A female and her cubs can flee from the slower male. If the male can get close to a cub, the mother may try to fight him off, sometimes at the cost of her life.{{sfn|Stirling|2011|p=212}}

Subadult bears, who are independent but not quite mature, have a particularly rough time as they are not as successful hunters as adults. Even when they do succeed, their kill will likely be stolen by a larger bear. Hence subadults have to scavenge and are often underweight and at risk of starvation. At adulthood, polar bears have a high survival rate, though adult males suffer injuries from fights over mates.{{sfn|Stirling|2011|pp=207–208}} Polar bears are especially susceptible to ''[[Biology:Trichinella|Trichinella]]'', a parasitic roundworm they contract through cannibalism.<ref>{{cite journal |last1=Larsen |first1=Thor |last2=Kjos-Hanssen |first2=Bjørn |year=1983 |title=''Trichinella'' sp. in polar bears from Svalbard, in relation to hide length and age |volume=1 |issue=1 |pages=89–96 |doi=10.1111/j.1751-8369.1983.tb00734.x |journal=Polar Research|doi-broken-date=28 January 2024 |bibcode=1983PolRe...1...89L |s2cid=208525641 }}</ref>

==Conservation status==
[[File:Polar Bear Habitat.png|thumb|right|Map from the U.S. Geological Survey shows projected changes in polar bear habitat from 2001 to 2010 and 2041 to 2050.<ref>{{cite report|last1=Durner|first1=George M.|last2=Douglas|first2=David C|last3=Nielson|first3=Ryan M|last4=Amstrup|first4=Steven C|last5=McDonald|first5=Trent L|year=2007|title=Predicting the Future Distribution of Polar Bear Habitat in the Polar Basin from Resource Selection Functions Applied to 21st Century General Circulation Model Projections of Sea Ice|publisher=USGS|url=https://polarbearscience.files.wordpress.com/2017/09/usgs_polarbear_durner_habitat_lowres.pdf|access-date=20 September 2023}}</ref>]]
In 2015, the [[Organization:IUCN Red List|IUCN Red List]] categorized the polar bear as ''[[Biology:Vulnerable species|vulnerable]]'' due to a "decline in area of occupancy, extent of occurrence and/or quality of habitat". It estimated the total population to be between 22,000 and 31,000, and the current population trend is unknown. Threats to polar bear populations include [[Earth:Climate change|climate change]], pollution and energy development.<ref name="iucn status 19 November 2021"/>

In 2021, the IUCN/SSC Polar Bear Specialist Group labelled four subpopulations (Barents and Chukchi Sea, Foxe Basin and Gulf of Boothia) as "likely stable", two (Kane Basin and M'Clintock Channel) as "likely increased" and three (Southern Beaufort Sea, Southern and Western Hudson Bay) as "likely decreased" over specific periods between the 1980s and 2010s. The remaining ten did not have enough data.<ref name=statusreport>{{cite report|title=Status Report on the World's Polar Bear Subpopulations: July 2021 Status Report|publisher=IUCN/SSC Polar Bear Specialist Group|date=July 2021|accessdate=2023-07-12|url=https://www.iucn-pbsg.org/wp-content/uploads/2021/11/July-2021-Status-Report-Web.pdf}}</ref> A 2008 study predicted two-thirds of the world's polar bears may disappear by 2050, based on the [[Physics:Arctic sea ice decline|reduction of sea ice]], and only one population would likely survive in 50 years.<ref>{{cite journal|last1=Amstrup|first1=S. C.|last2=Marcot|first2=B. G.|last3=Douglas|first3=D. C.|year=2008|title=A Bayesian network modeling approach to forecasting the 21st century worldwide status of polar bears|journal=Geophysical Monograph Series|volume=180|pages=213–268 |doi=10.1029/180GM14|bibcode=2008GMS...180..213A |isbn=9781118666470 }}</ref> A 2016 study projected a likely decline in polar bear numbers of more than 30 percent over three generations. The study concluded that declines of more than 50 percent are much less likely.<ref>{{cite journal|last1=Regehr|first1=E. V.|last2=Laidre|first2=K. L.|last3=Akçakaya|first3=H. R.|last4=Amstrup|first4=S. C.|last5=Atwood|first5=T. C.|last6=Lunn|first6=N. J.|last7=Obbard|first7=M.|last8=Stern|first8=H.|last9=Thiemann|first9=G. W.|last10=Wiig|first10=Ø|year=2016|title=Conservation status of polar bears (''Ursus maritimus'') in relation to projected sea-ice declines|journal=Biology Letters|volume=12|issue=12 |page=20160556|doi=10.1098/rsbl.2016.0556|pmid=27928000 |pmc=5206583 }}</ref> A 2012 review suggested that polar bears may become regionally extinct in southern areas by 2050 if trends continue, leaving the Canadian Archipelago and northern Greenland as strongholds.<ref name=2012review>{{cite journal|last1=Stirling|first1=I.|last2=Derocher|first2=A. E.|year=2012|title=Effects of climate warming on polar bears: a review of the evidence|journal=Global Change Biology|volume=18|issue=9|pages=2694–2706|doi=10.1111/j.1365-2486.2012.02753.x|pmid=24501049|bibcode=2012GCBio..18.2694S|s2cid=205294317|doi-access=free}}</ref>

The key danger from climate change is malnutrition or starvation due to [[Earth:Habitat destruction|habitat loss]]. Polar bears hunt seals on the sea ice, and rising temperatures cause the 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. Thinner sea ice tends to break more easily, which makes 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. Lack of access to seals also causes bears to find food on land which increases the risk of conflict with humans.<ref name="derocher2004" /><ref name=2012review/> 
[[File:Polar bear arctic.JPG|thumb|left|Polar bear swimming. The loss of sea ice has led to more open water and more pressure on the bears to swim great distances.<ref name="derocher2004" /><ref name=2012review/>]]
Reduction in sea ice cover also forces bears to swim longer distances, which further depletes their energy stores and occasionally leads to drowning. Increased ice mobility may result in less stable sites for dens or longer distances for mothers travelling to and from dens on land. Thawing of [[Earth:Permafrost|permafrost]] would lead to more fire-prone roofs for bears denning underground. Less snow may affect insulation while more rain could cause more cave-ins.<ref name="derocher2004"/><ref name=2012review/> The maximum corticosteroid-binding capacity of corticosteroid-binding globulin in polar bear serum correlates with stress in polar bears, and this has increased with climate warming.<ref>{{cite journal|last1=Boonstra|first1=R.|last2=Bodner|first2=K.|last3=Bosson|first3=C.|last4=Delehanty|first4=B.|last5=Richardson|first5=E. S.|last6=Lunn|first6=N. J.|last7=Derocher|first7=A. E.|last8=Molnár|first8=P. K.|year=2020|title=The stress of Arctic warming on polar bears|journal=Global Change Biology|volume=26|issue=8|pages=4197–4214|doi=10.1111/gcb.15142|pmid=32364624|bibcode=2020GCBio..26.4197B|s2cid=218492928}}</ref> Disease-causing [[Biology:Bacteria|bacteria]] and [[Biology:Parasite|parasite]]s would flourish more readily in a warmer climate.<ref name=2012review/>

Oil and gas development also affects polar bear habitat. The Chukchi Sea Planning Area of northwestern Alaska, which has had many drilling leases, was found to be an important site for non-denning female bears.<ref>{{cite journal|last1=Wilson|first1=R. R.|last2=Horne|first2=J. S.|last3=Rode|first3=K. D.|last4=Regher|first4=E. V.|last5=Durner|first5=G. M.|year=2014|title=Identifying polar bear resource selection patterns to inform offshore development in a dynamic and changing Arctic|journal=Ecosphere|volume=5|issue=10|pages=1–24|doi=10.1890/ES14-00193.1|doi-access=free|bibcode=2014Ecosp...5..136W }}</ref> [[Earth:Oil spill|Oil spill]]s are also a risk. A 2018 study found that ten percent or less of prime bear habitat in the Chukchi Sea is vulnerable to a potential spill, but a spill at full reach could impact nearly 40 percent of the polar bear population.<ref>{{cite journal|last1=Wilson|first1=R. R.|last2=Perham|first2=C.|last3=French-McCay|first3=D. P.|last4=Balouskus|first4=R.|year=2018|title=Potential impacts of offshore oil spills on polar bears in the Chukchi Sea|journal=Environmental Pollution|volume=235|pages=652–659|doi=10.1016/j.envpol.2017.12.057|pmid=29339335|url=https://digitalcommons.unl.edu/usfwspubs/524 }}</ref> Polar bears accumulate high levels of persistent organic pollutants such as [[Chemistry:Polychlorinated biphenyl|polychlorinated biphenyl]] (PCBs) and chlorinated pesticides, due to their position at the top of the [[Earth:Ecological pyramid|ecological pyramid]]. Many of these chemicals have been internationally banned due to the recognition of their harm to the environment. Traces of them have slowly dwindled in polar bears but persist and have even increased in some populations.<ref>{{cite journal|last1=Routti|first1=H.|last2=Atwood|first2=T.|last3=Bechshoft|first3=T.|last4=Boltunov|first4=A.|last5=Ciesielski|first5=T. M.|last6=Desforges|first6=J-P|last7=Dietz|first7=R.|last8=Gabrielsen|first8=G. W.|last9=Jenssen|first9=B. M.|last10=Letcher|first10=R. J.|last11=McKinney|first11=M. A.|last12=Morris|first12=A. D.|last13=Rigét|first13=F. F.|last14=Sonne|first14=C.|last15=Styrishave|first15=B.|last16=Tartu|first16=S.|year=2019|title=State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic|journal=Science of the Total Environment|volume=664|pages=1063–1083|doi=10.1016/j.scitotenv.2019.02.030|pmid=30901781|bibcode=2019ScTEn.664.1063R|s2cid=85457329|doi-access=free}}</ref>

Polar bears receive some legal protection in all the countries they inhabit. The species has been labelled as ''threatened'' under the US Endangered Species Act since 2008,<ref>{{cite web|title=Polar Bear Interaction Guidelines|website=U.S. Fish & Wildlife Service|accessdate=2023-07-12|url=https://www.fws.gov/pb-interaction-guidelines#:~:text=Polar%20bears%20are%20protected%20under,is%20necessary%20for%20human%20safety}}</ref> while the Committee on the Status of Endangered Wildlife in Canada listed it as of 'Special concern' since 1991.<ref>{{cite web|title=COSEWIC Assessment and Status Report on the Polar Bear (''Ursus maritimus'') in Canada 2018|website=Government of Canada|date=25 November 2019 |accessdate=2023-07-12|url=https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/polar-bear-2018.html}}</ref> In 1973, the Agreement on the Conservation of Polar Bears was signed by all five nations with polar bear populations, Canada, Denmark (of which Greenland is an autonomous territory), Russia (then USSR), Norway and the US. This banned most harvesting of polar bears, allowed indigenous hunting using traditional methods, and promoted the preservation of bear habitat.<ref name=International1973>{{cite journal|last1=Prestrud|first1=P.|last2=Stirling|first2=I.|year=1994|title=The International Polar Bear Agreement and the current status of polar bear conservation|journal=Aquatic Mammals|volume=20|issue=3|pages=113–124|url=https://www.researchgate.net/publication/285729154}}</ref> The [[Biology:CITES|Convention on International Trade in Endangered Species of Wild Fauna]] lists the species under Appendix II,<ref name="CITES"/> which allows regulated trade.<ref>{{cite web|url=https://cites.org/eng/disc/how.php|title=How CITES works|access-date=2023-07-29|website=CITES.org}}</ref>

==Relationship with humans==
Polar bears have coexisted and interacted with circumpolar peoples for millennia.{{sfn|Fee|2019|pp=25–26}} "White bears" are mentioned as commercial items in the Japanese book ''[[Religion:Nihon Shoki|Nihon Shoki]]'' in the seventh century. It is not clear if these were polar bears or white-coloured brown bears.{{sfn|Engelhard|2017|p=30}} During the [[History:Middle Ages|Middle Ages]], Europeans considered white bears to be a novelty and were more familiar with brown- and black-coloured bears.{{sfn|Ellis|2009|pp=13}} The first known written account of the polar bear in its natural environment is found in the 13th-century anonymous Norwegian text ''Konungs skuggsjá'', which mentions that "the white bear of Greenland wanders most of the time on the ice of the sea, hunting seals and whales and feeding on them" and says the bear is "as skillful a swimmer as any seal or whale".{{sfn|Engelhard|2017|p=53}} 
[[File:Richard Westall (1765-1836) - Nelson and the Bear - BHC2907 - Royal Museums Greenwich.jpg|thumb|right|''Nelson and the bear'', by Richard Westall (1773)]]
Over the next centuries, several European explorers would mention polar bears and describe their habits.{{sfn|Engelhard|2017|pp=53-66}}{{sfn|Ellis|2009|pp=14–23}} Such accounts became more accurate after the [[Philosophy:Age of Enlightenment|Enlightenment]], and both living and dead specimens were brought back. Nevertheless, some fanciful reports continued, including the idea that polar bears cover their noses during hunts. A relatively accurate drawing of a polar bear is found in Henry Ellis's work ''A Voyage to Hudson's Bay'' (1748).{{sfn|Engelhard|2017|pp=49, 51–52}} Polar bears were formally classified as a species by Constantine Phipps after his 1773 voyage to the Arctic. Accompanying him was a young Horatio Nelson, who was said to have wanted to get a polar bear coat for his father but failed in his hunt.{{sfn|Fee|2019|p=41}} In his 1785 edition of ''Histoire Naturelle'', Comte de Buffon mentions and depicts a "sea bear", clearly a polar bear, and "land bears", likely brown and black bears. This helped promote ideas about [[Biology:Speciation|speciation]]. Buffon also mentioned a "white bear of the forest", possibly a Kermode bear.{{sfn|Engelhard|2017|p=50}}

===Exploitation===
[[File:Eskimo hunter and polar bear slain with bow and arrow LCCN2005691848 (cropped).jpg|thumb|left|Hunter with polar bear slain with bow and arrow in Alaska (1924)]]
Polar bears were hunted as early as 8,000 years ago, as indicated by archaeological remains at Zhokhov Island in the [[Earth:East Siberian Sea|East Siberian Sea]]. The oldest graphic depiction of a polar bear shows it being hunted by a man with three dogs. This rock art was among several petroglyphs found at Pegtymel in Siberia and dates from the fifth to eighth centuries. Before access to firearms, native people used lances, bows and arrows and hunted in groups accompanied by dogs. Though hunting typically took place on foot, some people killed swimming bears from boats with a harpoon. Polar bears were sometimes killed in their dens. Killing a polar bear was considered a [[Religion:Rite of passage|rite of passage]] for boys in some cultures. Native people respected the animal and hunts were subject to strict rituals.{{sfn|Engelhard|2017|pp=122–124, 130, 133}}  Bears were harvested for the fur, meat, fat, tendons, bones and teeth.{{sfn|Fee|2019|p=28}}{{sfn|Engelhard|2017|p=128}} The fur was worn and slept on, while the bones and teeth were made into tools. For the Netsilik, the individual who finally killed the bear had the right to its fur while the meat was passed to all in the party. Some people kept the cubs of slain bears.{{sfn|Engelhard|2017|pp=127–128, 132}}
[[File:Greenland-polarbear-skin hg.jpg|thumb|right|Skins of hunted bears in Greenland]]
Norsemen in Greenland traded polar bear furs in the Middle Ages.{{sfn|Engelhard|2017|pp=34–35}} Russia traded polar bear products as early as 1556, with Novaya Zemlya and Franz Josef Land being important commercial centres. Large-scale hunting of bears at Svalbard occurred since at least the 18th century, when no less than 150 bears were killed each year by Russian explorers. In the next century, more Norwegians were harvesting the bears on the island. From the 1870s to the 1970s, around 22,000 of the animals were hunted in total. Over 150,000 polar bears in total were either killed or captured in Russia and Svalbard, from the 18th to the 20th century. In the Canadian Arctic, bears were harvested by commercial whalers especially if they could not get enough whales. The Hudson's Bay Company is estimated to have sold 15,000 polar bear coats between the late 19th century and early 20th century.{{sfn|Stirling|2011|pp=246–249}} In the mid-20th century, countries began to regulate polar bear harvesting, culminating in the 1973 agreement.<ref name=International1973/>

Polar bear meat was commonly eaten as rations by explorers and sailors in the Arctic. Its taste and texture have been described both positively and negatively. Some have called it too coarse with a powerful smell, while others praised it as a "royal dish".{{sfn|Engelhard|2017|p=141}} The liver was known for being too toxic to eat. This is due to the accumulation of [[Chemistry:Vitamin A|vitamin A]] from their prey.{{sfn|Derocher|2012|p=27}} Polar bear fat was also used in lamps when other fuel was unavailable.{{sfn|Engelhard|2017|p=141}} Polar bear rugs were almost ubiquitous on the floors of Norwegian churches by the 13th and 14th centuries. In more modern times, classical Hollywood actors would pose on bearskin rugs, notably Marilyn Monroe. Such images often had sexual connotations.{{sfn|Fee|2019|pp=32, 131–133}}

===Conflicts===
[[File:Polar-Bear-Warning-Longyearbyen.jpg|thumb|right|Road sign warning about the presence of polar bears. The Norwegian text translates into "Applies to all of Svalbard".]]
When the sea ice melts, polar bears, particularly subadults, conflict with humans over resources on land.<ref name=Heenskerk2020>{{cite journal|last1=Heemskerk|first1=S.|last2=Johnson|first2=A. C.|last3=Hedman|first3=D.|last4=Trim|first4=V.|last5=Lunn|first5=N. J.|last6=McGeachy|first6=D.|last7=Derocher|first7=A. E.|year=2020|title=Temporal dynamics of human-polar bear conflicts in Churchill, Manitoba|journal=Global Ecology and Conservation|volume=24|page=e01320|doi=10.1016/j.gecco.2020.e01320|s2cid=225123070|doi-access=free}}</ref> They are attracted to the smell of human-made foods, particularly at garbage dumps and may be shot when they encroach on private property.<ref>{{cite journal|last1=Clark|first1=D. A.|last2=van Beest|first2=F. M.|last3=Brook|first3=R. K.|year=2012|title=Polar Bear-human conflicts: state of knowledge and research needs|journal=Canadian Wildlife Biology and Management|volume=1|issue=1|pages=21–29|url=https://cwbm.ca/polar-bear-human-conflicts-state-of-knowledge-and-research-needs/}}</ref> In Churchill, Manitoba, local authorities maintain a "polar bear jail" where nuisance bears are held until the sea ice freezes again.<ref>{{cite web |title=Inside Canada's polar bear 'jail' where bears go without food and are kept behind bars — but it's not what you might think |date=13 May 2023 |first=Crystal |last=Raypole |website=Business Insider |url=https://www.businessinsider.com/inside-polar-bear-jail-churchill-canada-holding-facility-2023-5|accessdate=3 September 2023}}</ref> Climate change has increased conflicts between the two species.<ref name=Heenskerk2020/> Over 50 polar bears swarmed a town in Novaya Zemlya in February 2019, leading local authorities to declare a state of emergency.<ref>{{cite news |last1=Stanley-Becker |first1=Isaac |title=A 'mass invasion' of polar bears is terrorizing an island town. Climate change is to blame. |url=https://www.washingtonpost.com/nation/2019/02/11/mass-invasion-polar-bears-is-terrorizing-an-island-town-climate-change-is-blame/?noredirect=on |accessdate=14 February 2019 |agency=washingtonpost |work=washingtonpost.com |date=11 February 2019}}</ref>

From 1870 to 2014, there were an estimated 73 polar bear attacks on humans, which led to 20 deaths. The majority of attacks were by hungry males, typically subadults, while female attacks were usually in defence of the young. In comparison to brown and American black bears, attacks by polar bears were more often near and around where humans lived. This may be due to the bears getting desperate for food and thus more likely to seek out human settlements. As with the other two bear species, polar bears are unlikely to target more than two people at once. Though popularly thought of as the most dangerous bear, the polar bear is no more aggressive to humans than other species.<ref name=Wilder2017>{{cite journal|last1=Wilder|first1=J. M.|last2=Vongraven|first2=D.|last3=Atwood|first3=T.|last4=Hansen|first4=B.|last5=Jessen|first5=A.|last6=Kochnev|first6=A.|last7=York|first7=G.|last8=Vallender|first8=R.|last9=Hedman|first9=D.|last10=Gibbons|first10=M.|year=2017|title=Polar bear attacks on humans: implications of a changing climate|journal=Wildlife Society Bulletin|volume=41|issue=3|pages=537−547|doi=10.1002/wsb.783|bibcode=2017WSBu...41..537W }}</ref>

===Captivity===
[[File:Polar Bear at DZ.jpg|thumb|right|Visitors observing polar bears underneath a plexiglass tunnel at the Detroit Zoo]]
The polar bear was a particularly sought-after species for exotic animal collectors due to being relatively rare and remote living, and its reputation as a ferocious beast.{{sfn|Engelhard|2017|pp=96}} It is one of the few marine mammals that can reproduce well in captivity.<ref name=Perrin>{{cite book|editor-first1=William F.|editor-last1=Perrin|editor-first2=Bernd |editor-last2= Wursig|editor-first3=J. G. M. 'Hans' |editor-last3=Thewissen|title=Encyclopedia of Marine Mammals|year=2009|publisher=Academic Press|isbn=978-0-08-091993-5|last1=Robeck|first1=T. R.|last2=O'Brien|first2=J. K.|last3=Obell|first3=D. K. |contribution=Captive Breeding|pages=178}}</ref> They were originally kept only by royals and elites. The Tower of London got a polar bear as early as 1252 under King Henry III. In 1609, [[Biography:James VI and I|James VI and I]] of Scotland, England and Ireland was given two polar bear cubs by the sailor Jonas Poole, who got them during a trip to [[Place:Svalbard|Svalbard]].{{sfn|Fee|2019|pp=32, 103, 105}} At the end of the 17th century, Frederick I of Prussia housed polar bears in menageries with other wild animals. He had their claws and canines removed to perform mock fights. Around 1726, Catherine I of Russia gifted two polar bears to Augustus II the Strong of Poland, who desired them for his animal collection.{{sfn|Engelhard|2017|pp=95}} Later, polar bears were displayed to the public in [[Biology:Zoo|zoo]]s and circuses.{{sfn|Fee|2019|pp=103, 108}} In early 19th century, the species was exhibited at the Exeter Exchange in London, as well as menageries in Vienna and Paris. The first zoo in North America to exhibit a polar bear was the Philadelphia Zoo in 1859.{{sfn|Engelhard|2017|pp=xii, 96–97}}

Polar bear exhibits were innovated by Carl Hagenbeck, who replaced cages and pits with settings that mimicked the animal's natural environment.  In 1907, he revealed a complex panoramic structure at the Tierpark Hagenbeck Zoo in Hamburg consisting of exhibits made of artificial snow and ice separated by moats. Different polar animals were displayed on each platform, giving the illusion of them living together. Starting in 1975, Hellabrunn Zoo in Munich housed its polar bears in an exhibit which consisted of a glass barrier, a house, concrete platforms mimicking ice floes and a large pool. Inside the house were maternity dens, and rooms for the staff to prepare and store the food. The exhibit was connected to an outdoor yard for extra room. Similar naturalistic and "immersive" exhibits were opened in the early 21st century, such as the "Arctic Ring of Life" at the Detroit Zoo and Ontario's Cochrane Polar Bear Habitat.{{sfn|Engelhard|2017|pp=7, 101, 105–106}}{{sfn|Fee|2019|p=118}} Many zoos in Europe and North America have stopped keeping polar bears due to the size and costs of their complex exhibits.{{sfn|Fee|2019|pp=120–121}} In North America, the population of polar bears in zoos reached its zenith in 1975 with 229 animals and declined in the 21st century.<ref>{{cite journal|last1=Curry|first1=E|last2=Safay|first2=S|last3=Meyerson|first3=R|last4=Roth|first4=T. L.|year=2015|title=Reproductive trends of captive polar bears in North American zoos: a historical analysis|journal=Journal of Zoo and Aquarium Research|volume=3|issue=3|pages=99–106|doi=10.19227/jzar.v3i3.133}}</ref>
[[File:Repetitie Nationaal Songfestival in Carré, Sylvia de Leur dresseert beren, Bestanddeelnr 926-2489.jpg|thumb|left|Performing polar bear at the 1973 ''Nationaal Songfestival'' in the Netherlands]]
Polar bears have been trained to perform in circuses. Bears in general, being large, powerful, easy to train and human-like in form, were widespread in circuses, and the white coat of polar bears made them particularly attractive. Circuses helped change the polar bear's image from a fearsome monster to something more comical. Performing polar bears were used in 1888 by Circus Krone in Germany and later in 1904 by the Bostock and Wombwell Menagerie in England. Circus director Wilhelm Hagenbeck trained up to 75 polar bears to slide into a large tank through a chute. He began performing with them in 1908 and they had a particularly well-received show at the Hippodrome in London. Other circus tricks performed by polar bears involved tightropes, balls, roller skates and motorcycles. One of the most famous polar bear trainers in the second half of the twentieth century was the East German Ursula Böttcher, whose small stature contrasted with that of the large bears. Starting in the late 20th century, most polar bear acts were retired and the use of these bears for the circus is now prohibited in the US.{{sfn|Engelhard|2017|pp=109–111, 116–119}}

Several captive polar bears gained celebrity status in the late 20th and early 21st century, notably Knut of the Berlin Zoological Garden, who was rejected by his mother and had to be hand-reared by zookeepers. Another bear, Binky of the Alaska Zoo in Anchorage, became famous for attacking two visitors who got too close.{{sfn|Engelhard|2017|pp=21–24, 105}}{{sfn|Fee|2019|pp=123–124, 145}} Captive polar bears may pace back and forth, a [[Biology:Stereotypy (non-human)|stereotypical behaviour]]. In one study, they were recorded to have spent 14 percent of their days pacing.<ref>{{cite journal|last1=Shepherdson|first1=D.|last2=Lewis|first2=K. D.|last3=Carlstead|first3=K.|last4=Bauman|first4=J.|last5=Perrin|first5=N.|year=2013|title=Individual and environmental factors associated with stereotypic behavior and fecal glucocorticoid metabolite levels in zoo housed polar bears|journal=Applied Animal Behaviour Science|volume=147|issue=3–4|pages=268–277|doi=10.1016/j.applanim.2013.01.001}}</ref> Gus of the Central Park Zoo was prescribed Prozac by a therapist for constantly swimming in his pool.{{sfn|Engelhard|2017|p=24}} To reduce stereotypical behaviours, zookeepers provide the bears with enrichment items to trigger their play behaviour.<ref>{{cite journal|last1=Canino|first1=W.|last2=Powell|first2=D.|year=2010|title=Formal behavioral evaluation of enrichment programs on a zookeeper's schedule: a case study with a polar bear (''Ursus maritimus'') at the Bronx Zoo|journal=Zoo Biology|volume=29|issue=4|pages=503–508|doi=10.1002/zoo.20247|pmid=19373879}}</ref> Zoo polar bears may appear green due to [[Biology:Algae|algae]] concentrations.<ref>{{cite journal|last1=Lewin|first1=R. A.|last2=Farnsworth|first2=P. A.|last3=Yamanaka|first3=G.|year=1981|title=The algae of green polar bears|journal=Phycologia|volume=20|issue=3 |pages=303–314|doi=10.2216/i0031-8884-20-3-303.1|bibcode=1981Phyco..20..303L }}</ref>

===Cultural significance===
{{Multiple image
| align             = right
| direction         = vertical
| width             = 200px
|image1=Ours nageant (Musée du quai Branly) (3034045389).jpg|caption1=Ivory carving of a swimming polar bear from the Dorset culture, northern Canada
|image2=Coat of arms of Greenland.svg|caption2=The coat of arms of Greenland
}}
Polar bears have prominent roles in Inuit culture and religion. The deity [[Unsolved:Torngarsuk|Torngarsuk]] is sometimes imagined as a giant polar bear. He resides underneath the sea floor in an [[Unsolved:Underworld|underworld]] of the dead and has power over sea creatures. Kalaallit shamans would worship him through singing and dancing and were expected to be taken by him to the sea and consumed if he considered them worthy. Polar bears were also associated with the goddess Nuliajuk who was responsible for their creation, along with other sea creatures. It is believed that shamans could reach the Moon or the bottom of the ocean by riding on a guardian spirit in the form of a polar bear. Some folklore involves people turning into or disguising themselves as polar bears by donning their skins or the reverse, with polar bears removing their  skins. In [[Unsolved:Inuit astronomy|Inuit astronomy]], the [[Astronomy:Pleiades|Pleiades]] star cluster is conceived of as a polar bear trapped by dogs while [[Astronomy:Orion's Belt|Orion's Belt]], the [[Astronomy:Hyades (star cluster)|Hyades]] and [[Astronomy:Aldebaran|Aldebaran]] represent hunters, dogs and a wounded bear respectively.{{sfn|Engelhard|2017|pp=152–153, 156–162}}

Nordic folklore and literature have also featured polar bears. In ''The Tale of Auðun of the West Fjords'', written around 1275, a poor man named Auðun spends all his money on a polar bear in Greenland, but ends up wealthy after giving the bear to the king of Denmark.{{sfn|Fee|2019|p=32}} In the 14th-century manuscript Hauksbók, a man named Odd kills and eats a polar bear that killed his father and brother. In the story of ''The Grimsey Man and the Bear'', a mother bear nurses and rescues a farmer stuck on an ice floe and is repaid with sheep meat. 18th-century Icelandic writings mention the legend of a "polar bear king" known as the {{lang|is|bjarndýrakóngur}}. This beast was depicted as a polar bear with "ruddy cheeks" and a unicorn-like horn, which glows in the dark. The king could understand when humans talk and was considered to be very astute.{{sfn|Engelhard|2017|pp=165–166, 181–182}} Two Norwegian fairy tales, "East of the Sun and West of the Moon" and "White-Bear-King-Valemon", involve white bears turning into men and seducing women.{{sfn|Fee|2019|p=98}}

Drawings of polar bears have been featured on maps of the northern regions. Possibly the earliest depictions of a polar bear on a map is the Swedish ''[[History:Carta marina|Carta marina]]'' of 1539, which has a white bear on Iceland or "Islandia". A 1544 map of North America includes two polar bears near Quebec. Notable paintings featuring polar bears include François-Auguste Biard's ''Fighting Polar Bears'' (1839) and Edwin Landseer's ''[[Unsolved:Man Proposes, God Disposes|Man Proposes, God Disposes]]'' (1864). Polar bears have also been filmed for cinema. An Inuit polar bear hunt was shot for the 1932 documentary ''Igloo'', while the 1974 film ''The White Dawn'' filmed a simulated stabbing of a trained bear for a scene. In the film ''The Big Show'' (1961), two characters are killed by a circus polar bear. The scenes were shot using animal trainers instead of the actors. In modern literature, polar bears have been characters in both children's fiction, like Hans Beer's ''Little Polar Bear and the Whales'' and Sakiasi Qaunaq's ''The Orphan and the Polar Bear'', and fantasy novels, like [[Biography:Philip Pullman|Philip Pullman]]'s ''His Dark Materials'' series. In radio, Mel Blanc provided the vocals for Jack Benny's pet polar bear Carmichael on ''The Jack Benny Program''.{{sfn|Engelhard|2017|pp=xi–xii, 36, 82–83, 100, 116, 184, 215}} The polar bear is featured on flags and coats of arms, like the coat of arms of Greenland, and in many advertisements, notably for Coca-Cola since 1922.{{sfn|Fee|2019|pp=32, 133–135}}

As [[Biology:Charismatic megafauna|charismatic megafauna]], polar bears have been used to raise awareness of the dangers of climate change. Aurora the polar bear is a giant marionette created by Greenpeace for climate protests.<ref name=Born2019>{{cite journal|last=Born|first=D.|year=2019|title=Bearing witness? Polar bears as icons for climate change communication in ''National Geographic''|journal=Environmental Communication|volume=13|issue=5|pages=649–663|doi=10.1080/17524032.2018.1435557|s2cid=150289699|doi-access=free|bibcode=2019Ecomm..13..649B }}</ref> The [[Organization:World Wide Fund for Nature|World Wide Fund for Nature]] has sold plush polar bears as part of its "Arctic Home" campaign.<ref>{{cite journal|last=Dunaway|first=F|year=2009|title=Seeing global warming: contemporary art and the fate of the planet|journal=Environmental History|volume=14|issue=1|pages=9–31|doi=10.1093/envhis/14.1.9}}</ref> Photographs of polar bears have been featured in ''National Geographic'' and ''{{wipe|Time (magazine)}}'' magazines, including ones of them standing on ice floes, while the climate change documentary and advocacy film ''An Inconvenient Truth'' (2006) includes an animated bear swimming.<ref name=Born2019/> Automobile manufacturer [[Company:Nissan|Nissan]] used a polar bear in one of its commercials, hugging a man for using an electric car.<ref>{{cite book|last1=Martinez|first1=D. E.|contribution=Polar bears, Inuit names, and climate citizenship|title=Culture, Politics and Climate Change In 2009|editor-first1=Deserai A.|editor-last1=Crow|editor-first2=Maxwell T|editor-last2=Boykoff|year=2014|publisher=Taylor & Francis|page=46|isbn=9781135103347}}</ref> To make a statement about global warming, in 2009 a Copenhagen ice statue of a polar bear with a bronze skeleton was purposely left to melt in the sun.{{sfn|Engelhard|2017|page=xiii}}

==See also==
* 2011 Svalbard polar bear attack
* International Polar Bear Day
* List of individual bears – includes individual captive polar bears
* [[Organization:Polar Bears International|Polar Bears International]] – conservation organization
* Polar Bear Shores – an exhibit featuring polar bears at Sea World in Australia

==Notes==
{{notelist}}

==References==
{{reflist}}

==Bibliography==
{{Refbegin}}
*{{cite book|last=Derocher|first=Andrew E.|year=2012|title=Polar Bears: A Complete Guide to Their Biology and Behavior|publisher=Johns Hopkins University Press|isbn=978-1-4214-0305-2}}
*{{cite book|last=Ellis|first=Richard|year=2009|title=On Thin Ice: The Changing World of the Polar Bear|publisher=Knopf|isbn=978-0-307-27059-7}}
*{{cite book|last=Engelhard|first=Richard|year=2017|title=Ice Bear: The Cultural History of an Arctic Icon|publisher=University of Washington Press|isbn=978-0-295-99922-7}}
*{{cite book|last=Fee|first=Margrey|year=2019|title=Polar Bear|publisher=Reaktion Books|isbn=978-1-78914-146-7}}
*{{cite book|last=Stirling|first=Ian|year=2011|title=Polar Bears: Natural History of a Threatened Species|publisher=Fitzhenry and Whiteside|isbn=978-1-55455-155-2}}
{{Refend}}

==External links==
* [https://polarbearsinternational.org/ Polar Bears International website]
* ARKive — [https://web.archive.org/web/20060317030045/http://www.arkive.org/species/GES/mammals/Ursus_maritimus/ images and movies of the polar bear (''Ursus maritimus'')]

{{Subject bar|portal1=Mammals|portal2=Animals|portal3=Biology|auto=1}}
{{Taxonbar|from=Q33609}}

{{DEFAULTSORT:Polar Bear}}
[[Category:Carnivorans of Europe]]
[[Category:Carnivorans of North America]]
[[Category:Carnivorans of Asia]]
[[Category:Vulnerable animals]]
[[Category:Vulnerable biota of Europe]]
[[Category:Vulnerable biota of Asia]]
[[Category:ESA threatened species]]

{{Sourceattribution|Polar bear}}