Examine individual changes

'{{Short description|Extinct genus of bears}} {{Automatic taxobox | name = Arctodus | fossil_range = [[Late Pliocene]] to [[Late Pleistocene]], {{fossil range|2.5|0.012}} | image = ArctodusSimusSkeleton.jpg | image_caption = ''A. simus'' from the [[La Brea tar pits]] | taxon = Arctodus | authority = [[Joseph Leidy|Leidy]], 1854 | type_species = {{extinct}}'''''Arctodus pristinus''''' | type_species_authority = [[Joseph Leidy|Leidy]], 1854 | subdivision_ranks = Other species | subdivision = *{{extinct}}'''''A. simus''''' <small>([[Edward Drinker Cope|Cope]], 1879)</small> | range_map = Short Faced Bear Range.png | range_map_caption = ''Arctodus simus'' range | synonyms = {{collapsible list|bullets=true|title=Species synonymy |{{collapsible list|bullets=true|title=''A. simus'': |''[[Arctotherium]] californicum'' {{small|[[John Campbell Merriam|Merriam]] 1911}} |''Arctotherium simum'' {{small|[[Edward Drinker Cope|Cope]] 1879}} |''Arctotherium yukonense'' {{small|[[Lawrence Lambe|Lambe]] 1911}} |''Dinarctotherium merriami'' {{small|[[Erwin Hinckley Barbour|Barbour]] 1916}} |''Tremarctotherium simum'' {{small|[[James W. Gidley|Gidley]] 1928}} }} |{{collapsible list|bullets=true|title=''A. pristinus'': |''Arctodus haplodon'' {{small|[[Oliver Perry Hay|Hay]] 1902}} |''[[Arctotherium]] pristinum'' {{small|[[Edward Drinker Cope|Cope]] 1895}} |''[[Ursus]] haplodon'' {{small|[[Edward Drinker Cope|Cope]] 1896}} |''[[Tremarctos]] haplodon'' {{small|[[Édouard Louis Trouessart|Trouessart]] 1897}} }} }} }}'''''Arctodus''''', or the '''North American short-faced bear''', is an extinct [[bear]] genus that inhabited [[North America]] from the [[Piacenzian|latest Pliocene]] to the [[Holocene]] epoch, from ~2.5 [[Year#mya|Mya]] until 12,000 years ago. Today considered to be an enormous omnivore, ''Arctodus'' was the most widespread [[short-faced bear]] in North America. There are two recognized species: the '''lesser short-faced bear''' (''Arctodus pristinus'') and the '''giant short-faced bear''' (''Arctodus simus''), with the latter considered to be one of the largest known terrestrial mammalian [[Carnivora|carnivorans]] that has ever existed. ==Taxonomy== ''Arctodus'' was first described by [[Joseph Leidy]] in 1854, with finds of ''A. pristinus'' from the [[Northbridge Park|Ashley Phosphate Beds]], [[South Carolina]].<ref name=":26" /><ref name=":5" /><ref>{{Cite journal |date=1879-08-01 |title=South Carolina Fossils |url=https://www.nature.com/articles/020354a0 |journal=Nature |language=en |volume=20 |issue=510 |pages=354–355 |doi=10.1038/020354a0 |s2cid=4034608 |issn=1476-4687}}</ref> The scientific name of the genus, ''Arctodus'', derives from [[Greek language|Greek]], and means "bear tooth". The first fossils of ''A. simus'' were found in the Potter Creek Cave, [[Shasta County, California|Shasta County]], [[California]], by J. A. Richardson in 1878, and were described by [[Edward Drinker Cope]] in 1879.<ref name=":48">{{cite journal | author = Cope E. D. | year = 1879 | title = The cave bear of California | journal = American Naturalist | volume = 13 | page = 791 }}</ref><ref>{{Cite journal |last=Feranec |first=Robert S. |date=2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |journal=Radiocarbon |volume=51 |issue=3 |pages=931–936 |doi=10.1017/S0033822200034007 |s2cid=131722109 |doi-access=free }}</ref><ref>{{Citation |last1=Merriam |first1=John C. |title=Relationships and Structure of the Short-Faced Bear, Arctotherium, from the Pleistocene of California |date=1925 |url=https://resolver.caltech.edu/CaltechAUTHORS:20191008-132308406 |pages=1–25 |place=Washington, DC |publisher=Carnegie institution of Washington |language=en |access-date=2022-05-06 |last2=Stock |first2=Chester}}</ref> The most nearly complete skeleton of ''A. simus'' found in the [[United States|US]] was unearthed in [[Fulton County, Indiana|Fulton County]], [[Indiana]]; the original bones are in the [[Field Museum of Natural History]], [[Chicago]].<ref name=":39">{{Cite book |last1=Richards |first1=Ronald L. |url=https://www.biodiversitylibrary.org/bibliography/3480 |title=Giant short-faced bear (Arctodus simus yukonensis) remains from Fulton County, northern Indiana |last2=Neiburger |first2=Ellis J. |last3=Turnbull |first3=William D. |date=1995 |publisher=Field Museum of Natural History |location=Chicago, Ill. }}</ref><ref>{{Cite book |last=Stark |first=Mike |url=https://books.google.com/books?id=hWhgEAAAQBAJ&dq=field+museum+rochester+arctodus&pg=PA122-IA12 |title=Chasing the Ghost Bear: On the Trail of America's Lost Super Beast |date=2022 |publisher=U of Nebraska Press |isbn=978-1-4962-2902-1 |pages=Fig. 19 }}</ref> In the 19th and early 20th centuries, specimens of ''Arctodus'' were occasionally referred to ''[[Arctotherium]]'', and visa versa.<ref>{{Cite web |title=Arctodus |url=https://www.utep.edu/leb/pleistnm/taxaMamm/Arctodus.htm#:~:text=Synonyms.,Arctotherium%20simum,%20Tremarctotherium%20simum |access-date=2022-05-05 |website=www.utep.edu}}</ref><ref>{{Cite book |last1=Spamer |first1=Earle E. |url=https://books.google.com/books?id=3loD7lTLBxgC&dq=Arctodus+haplodon&pg=PA204 |title=A Study of Fossil Vertebrate Types in the Academy of Natural Sciences of Philadelphia: Taxonomic, Systematic, and Historical Perspectives |last2=Daeschler |first2=Edward |last3=Philadelphia |first3=Academy of Natural Sciences of |last4=Vostreys-Shapiro |first4=L. Gay |date=1995 |publisher=Academy of Natural Sciences |isbn=978-0-910006-51-4 |language=en}}</ref><ref>{{Cite book |last=Hay |first=Oliver Perry |url=https://books.google.com/books?id=mkMZAAAAYAAJ&q=haplodon&pg=PA763 |title=Bibliography and Catalogue of the Fossil Vertebrata of North America |date=1901 |publisher=U.S. Government Printing Office |language=en}}</ref><ref>{{Citation |last1=Merriam |first1=John C. |title=Relationships and Structure of the Short-Faced Bear, Arctotherium, from the Pleistocene of California |date=1925 |url=https://resolver.caltech.edu/CaltechAUTHORS:20191008-132308406 |pages=1–25 |place=Washington, DC |publisher=Carnegie institution of Washington |language=en |access-date=2022-06-09 |last2=Stock |first2=Chester}}</ref> However, today neither genera are considered to have overlapped, with the closest point of contact being [[Mexico|México]]; the giant ''Arctodus simus'' in [[Hueyatlaco|Valsequillo]], [[Puebla]], and the smaller ''[[Arctotherium|Arctotherium wingei]]'' in the [[Yucatán Peninsula]].<ref name=":35">{{Cite journal |last=Ferrusquía-Villafranca |first=Ismael |last2=Arroyo-Cabrales |first2=Joaquín |last3=Martínez-Hernández |first3=Enrique |last4=Gama-Castro |first4=Jorge |last5=Ruiz-González |first5=José |last6=Polaco |first6=Oscar J. |last7=Johnson |first7=Eileen |date=2010-04-15 |title=Pleistocene mammals of Mexico: A critical review of regional chronofaunas, climate change response and biogeographic provinciality |url=https://www.sciencedirect.com/science/article/pii/S104061820900442X |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |language=en |volume=217 |issue=1 |pages=53–104 |doi=10.1016/j.quaint.2009.11.036 |issn=1040-6182}}</ref><ref>{{Cite journal |last=Arroyo-Cabrales |first=Joaquín |last2=Polaco |first2=Oscar J. |last3=Johnson |first3=Eileen |last4=Ferrusquía-Villafranca |first4=Ismael |date=2010-02-01 |title=A perspective on mammal biodiversity and zoogeography in the Late Pleistocene of México |url=https://www.sciencedirect.com/science/article/pii/S1040618209001633 |journal=Quaternary International |series=Quaternary Changes of Mammalian Communities Across and Between Continents |language=en |volume=212 |issue=2 |pages=187–197 |doi=10.1016/j.quaint.2009.05.012 |issn=1040-6182}}</ref><ref name=":25" /> Conversely, fossils of ''Arctodus pristinus'' are often confused with the similarly sized, partially contemporaneous [[Tremarctinae|short-faced bear]], ''[[Tremarctos floridanus]]''.<ref name=":26" /> Sometimes described as the "American cave bear", ''Arctodus'' should not be mistaken for the similarly large [[Cave bear|Eurasian cave bear]] (''Ursus speleaus'').<ref name=":48" /> As an ursine, the Eurasian cave bear last shared a common ancestor with the tremarctine ''Arctodus'' circa 13.4 million years ago.<ref name="Pedersen 2728–2736.e8" /> ===Evolution=== {{Cladogram|{{clade| style=font-size:90%;line-height:90%; |1={{dagger}}[[Hemicyoninae]] |2={{Clade |1={{dagger}}[[Ursavinae]] |2={{Clade |1={{dagger}}[[Agriotheriinae]] |2={{Clade |1=[[Ailuropodinae]] [[File:Recherches pour servir à l'histoire naturelle des mammifères (Pl. 50) (white background).jpg|75px]] |2={{Clade |1=[[Ursinae]] [[File:Ursus arctos - 1700-1880 - Print - Iconographia Zoologica - Special Collections University of Amsterdam - (white background).jpg|75px]] |2={{Clade |label1=[[Tremarctinae]] (short-faced bears) |1={{Clade |1={{dagger}}''[[Plionarctos]]'' |2={{Clade |1={{dagger}}'''''Arctodus''''' |2={{Clade |1=''[[Tremarctos]]'' [[File:Spectacled bear (1829).jpg|75px]] |2={{dagger}}''[[Arctotherium]]'' }} }} }} }} }} }} }} }} }}|title=[[Tremarctinae]] within [[Ursidae]]|align=left}} ''Arctodus'' belongs to a group of bears known as the short-faced bears ([[Tremarctinae]]), which appeared in [[North America]] during the earliest parts of the late [[Miocene]] epoch in the form of ''[[Plionarctos]]'', a genus considered ancestral to [[Tremarctinae]]. ''[[Plionarctos]]'' gave way to the medium sized ''Arctodus pristinus,'' ''[[Tremarctos floridanus]]'' and ''Arctotherium sp.'' in the [[Piacenzian|Late Pliocene]] of [[North America]], <ref name=":5">{{cite journal |last1=Emslie |first1=Steven D. |year=1995 |title=The fossil record of Arctodus pristinus (Ursidae: Tremarctinae) in Florida |journal=Bulletin of the Florida Museum of Natural History |volume=37 |pages=501–514 |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |s2cid=168164209 }}</ref><ref name=":18">{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Romero |first2=M.R. Aguilar |date=2008-10-14 |title=A Blancan (Pliocene) short-faced bear from El Salvador and its implications for Tremarctines in South America |journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen |volume=250 |issue=1 |pages=1–8 |doi=10.1127/0077-7749/2008/0250-0001 |url=http://sedici.unlp.edu.ar/handle/10915/5361 }}</ref><ref name=":0" /> with the divergence date for ''Arctodus'' being ~5.5 million years ago.<ref name="Pedersen 2728–2736.e8" /> Both ''Arctodus'' and ''[[Tremarctos]]'' were largely restricted to the more forested eastern part of the continent, as ''[[Borophagus|Boropahgus]]'' and ''[[Agriotherium]]'' are thought to have limited [[Tremarctinae|tremarctine]] presence in the more open Western [[North America]]. ''[[Tremarctos floridanus]]'' established a range mostly hugging the [[Gulf of Mexico|Gulf Coast]] (but also extending to [[California]] and [[Idaho]]),<ref name=":0" /> whereas ''Arctodus pristinus'' ranged from [[Aguascalientes]], [[Mexico]],<ref>{{Cite journal |last1=Dalquest |first1=W. W. |last2=Mooser |first2=O. |date=1980-12-19 |title=Arctodus pristinus Leidy in the Pleistocene of Aguascalientes, Mexico |journal=Journal of Mammalogy |volume=61 |issue=4 |pages=724–725 |doi=10.2307/1380320 |jstor=1380320 }}</ref> to [[New Jersey]] in the [[United States|US]].<ref name=":6">I. Ferrusquia-Villafranca. 1978. Bol Univ Nac Aut Mex Inst Geol 101:193-321</ref> Perhaps due to their evolutionary history, both ''[[Tremarctos floridanus]]'' and ''Arctodus pristinus'' have the greatest concentration of fossils in [[Florida]]- in particular, the [[Santa Fe River (Florida)|Santa Fe River 1 site]] of [[Gilchrist County, Florida|Gilchrist County]]. However, in the [[Quaternary|early Quaternary]], when both ''[[Borophagus]]'' and ''[[Agriotherium]]'' went extinct, ''Arctodus'' would take advantage and spread into the rest of the continent, primarily in the form of ''A. simus''. Concurrently, during the [[Great American Interchange]] that followed the joining of North and South America, the [[Central America]]n based ''Arctotherium'' invaded [[South America]],<ref name=":18" /> leading to the diversification of the genus, including the colossal ''[[Arctotherium|Arctotherium angustidens]]''. At the onset of the [[Chibanian|Middle Pleistocene]] ([[Kansan glaciation|Kansan age]], ~800,000 years ago), the smaller ''A. pristinus'' was joined by the enormous ''A. simus''.<ref name=":0">{{Cite journal|last1=Schubert|first1=Blaine|last2=Hulbert|first2=Richard|last3=MacFadden|first3=Bruce|last4=Searle|first4=Michael|last5=Searle|first5=Seina|date=2010-01-01|title=Giant Short-faced Bears (Arctodus simus) in Pleistocene Florida USA, a Substantial Range Extension|url=https://www.researchgate.net/publication/250071137|journal=Journal of Paleontology|volume=84|pages=79–87|doi=10.1666/09-113.1|s2cid=131532424}}</ref> The two are differentiated not only by size, but also by the shorter snout, more robust teeth and longer limbs of ''A. simus,'' and the relative proportions of each species' molars and premolars. However, there are relatively few morphological differences. As a result, differentiating ''Arcotdus simus'' from ''Arctodus pristinus'' can be difficult, as large individuals of ''Arctodus pristinus'' can overlap in size with small individuals of ''Arctodus simus''.<ref name=":0" /> Although both species co-existed for at least half a million years (''A. pristinus'' went extinct ~300,000 BP),<ref name=":0" /> there is no direct evidence of [[sympatry]] or [[Competition (biology)|competition]] in the fossil record as of yet.<ref name=":0" /> However, there are unreliable records of ''A. pristinus'' in [[South Carolina]], [[California]] and [[Florida]] in the [[Late Pleistocene]], suggesting a possible existence as a [[Relict (biology)|relict species]] in [[Refugium (population biology)|refugia]] until the [[Quaternary extinction|Quaternary extinction event]].<ref>{{Cite journal |last1=Feranec |first1=Robert S. |last2=Hadly |first2=Elizabeth A. |last3=Blois |first3=Jessica L. |last4=Barnosky |first4=Anthony D. |last5=Paytan |first5=Adina |date=2007 |title=Radiocarbon Dates from the Pleistocene Fossil Deposits of Samwel Cave, Shasta County, California, USA |journal=Radiocarbon |volume=49 |issue=1 |pages=117–121 |doi=10.1017/S0033822200041941 |s2cid=130708736 |doi-access=free }}</ref><ref name=":8">{{Cite book |last=Sanders |first=Albert E. |url=https://books.google.com/books?id=LS8LAAAAIAAJ&dq=pristinus+south+carolina&pg=PA48 |title=Additions to the Pleistocene Mammal Faunas of South Carolina, North Carolina, and Georgia |date=2002 |publisher=American Philosophical Society |isbn=978-0-87169-925-1 }}</ref><ref name=":9">{{Cite journal |last1=Esker |first1=Donald |last2=Wilkins |first2=William |last3=Agenbroad |first3=Larry |date=2010-08-13 |title=ESKER, WILKINS, AND AGENBROAD—MULTIVARIATE ANALYSIS OF URSIDS A multivariate analysis of the ecology of North American Pleistocene bears, with a focus on Arctodus simus |url=https://www.researchgate.net/publication/314037201}}</ref> Likewise, ''Arctodus simus'' is relatively poorly known from the [[Irvingtonian]] (800,000 BP-250,000 BP) with finds only from Texas, Nebraska and California.<ref name=":46" /> In any case, whereas ''A. pristinus'' seems to have preferred the more heavily forested thermal enclave in eastern North America,<ref name=":10">{{Cite journal |last1=Russell |first1=Dale A. |last2=Rich |first2=Fredrick J. |last3=Schneider |first3=Vincent |last4=Lynch-Stieglitz |first4=Jean |date=May 2009 |title=A warm thermal enclave in the Late Pleistocene of the South-eastern United States |journal=Biological Reviews |volume=84 |issue=2 |pages=173–202 |doi=10.1111/j.1469-185X.2008.00069.x |pmid=19391200 |s2cid=9609391 }}</ref> ''A. simus'' was a cosmopolitan, eventually pan-continental species in the Late Pleistocene- sharing that distinction with the [[American black bear|black bear]], and the [[brown bear]] after 100,000 BP.<ref name=":9" /> Primarily inhabiting a range from southern [[Canada]] to [[Puebla|Central Mexico]] in the west, to [[Pennsylvania]] and [[Florida]] in the east,<ref name=":25">{{Cite book|last1=Richards|first1=Ronald L. |title=Distribution and size variation in North American Short-faced bears, Arctodus simus|last2=Churcher|first2=C. S.|last3=Turnbull|first3=William D.|date=2019-11-18|publisher=University of Toronto Press|isbn=978-1-4875-7415-4 |doi=10.3138/9781487574154-012}}</ref><ref name=":0" /><ref>{{Cite journal |last1=Steffen |first1=Martina L. SteffenM L. |last2=Harington |first2=C. R. HaringtonC R. |date=2010-07-23 |title=Giant short-faced bear (Arctodus simus) from late Wisconsinan deposits at Cowichan Head, Vancouver Island, British Columbia |url=https://cdnsciencepub.com/doi/abs/10.1139/E10-018 |journal=Canadian Journal of Earth Sciences |volume=47 |issue=8 |pages=1029–1036 |language=en |doi=10.1139/E10-018}}</ref><ref>{{cite journal | author = Cassiliano M. L. | year = 1999 | title = Biostratigraphy of Blancan and Irvingtonian mammals in the Fish Creek-Vallecito Creek section, southern California, and a review of the Blancan-Irvingtonian boundary | journal = Journal of Vertebrate Paleontology | volume = 19 | issue = 1| pages = 169–186 | doi=10.1080/02724634.1999.10011131}}</ref><ref>{{cite journal |last1=Carranza-Castañeda |first1=Oscar |last2=Miller |first2=Wade E. |title=Rediscovered type specimens and other important published Pleistocene mammalian fossils from Central Mexico |journal=Journal of Vertebrate Paleontology |date=16 September 1987 |volume=7 |issue=3 |pages=335–341 |doi=10.1080/02724634.1987.10011664 }}</ref><ref name=":24">{{Cite journal |last1=Holliday |first1=Vance |last2=Surovell |first2=Todd |last3=Meltzer |first3=David |last4=Grayson |first4=Donald |last5=Boslough |first5=Mark |date=2014-08-01 |title=The Younger Dryas impact hypothesis: A cosmic catastrophe |url=https://www.researchgate.net/publication/265132201 |journal=Journal of Quaternary Science |volume=29 |issue=6 |pages=515–530 |doi=10.1002/jqs.2724|s2cid=18644154 }}</ref> ''A. simus'' is particularly famous from fossils found in the [[La Brea tar pits]] in southern [[California]].<ref name="Bearalmanac">{{cite book | author = Brown, Gary | title = Great Bear Almanac | year = 1996 | isbn = 978-1558214743 | page = [https://archive.org/details/greatbearalmanac00gary/page/340 340] | url-access = registration |url=https://archive.org/details/greatbearalmanac00gary/page/340 }}</ref> From ~44,000 BP to ~23,000 BP, ''A. simus'' also inhabited [[Beringia]]- finds today span from northern [[Alaska]] to the [[Yukon]].<ref name=":0" /><ref name=":24" /><ref>C. S. Churcher, A. V. Morgan, and L. D. Carter. 1993. ''Arctodus simus from the Alaskan Arctic Slope''. Canadian Journal of Earth Sciences 30(5):1007-1013, collected by A. V. Morgan</ref> The [[Late Pleistocene]] represents the peak of [[Bear|ursid]] diversity in [[Quaternary]] [[North America]], with ''Arctodus simus,'' [[brown bear]]s, [[American black bear|black bears]], ''[[Tremarctos floridanus]]'', and ''[[Arctotherium|Arctotherium wingei]]'' all roaming south of the [[Laurentide Ice Sheet]],<ref name=":19">{{cite journal |last1=Salis |first1=Alexander T |last2=Bray |first2=Sarah C E |last3=Lee |first3=Michael S Y |last4=Heiniger |first4=Holly |last5=Barnett |first5=Ross |last6=Burns |first6=James A |last7=Doronichev |first7=Vladimir |last8=Fedje |first8=Daryl |last9=Golovanova |first9=Liubov |last10=Harington |first10=C Richard |last11=Hockett |first11=Bryan |last12=Kosintsev |first12=Pavel |last13=Lai |first13=Xulong |last14=Mackie |first14=Quentin |last15=Vasiliev |first15=Sergei |last16=Weinstock |first16=Jacobo |last17=Yamaguchi |first17=Nobuyuki |last18=Meachen |first18=Julie |last19=Cooper |first19=Alan |last20=Mitchell |first20=Kieren J |title=Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge |date=3 September 2020 |doi=10.1101/2020.09.03.279117 |s2cid=221510369 |url=https://www.biorxiv.org/content/biorxiv/early/2020/09/03/2020.09.03.279117.full.pdf }}</ref><ref>{{Cite journal|last1=Schubert|first1=Blaine W.|last2=Chatters|first2=James C.|last3=Arroyo-Cabrales|first3=Joaquin|last4=Samuels|first4=Joshua X.|last5=Soibelzon|first5=Leopoldo H.|last6=Prevosti|first6=Francisco J.|last7=Widga|first7=Christopher|last8=Nava|first8=Alberto|last9=Rissolo|first9=Dominique|last10=Erreguerena|first10=Pilar Luna|date=May 2019|title=Yucatán carnivorans shed light on the Great American Biotic Interchange|journal=Biology Letters|volume=15|issue=5|pages=20190148|doi=10.1098/rsbl.2019.0148 |pmc=6548739|pmid=31039726}}</ref> and [[polar bear]]s above the ice.<ref>{{Cite journal|last1=Arroyo-Cabrales|first1=Joaquin|last2=Johnson|first2=Eileen|last3=Graham|first3=Ruswell|last4=perez crespo|first4=Victor|date=2016-07-24|title=North American ursid (Mammalian: Ursidae) defaunation from Pleistocene to recent.|url=https://www.researchgate.net/publication/305681538|journal=Cranium|volume=33|pages=51–56}}</ref><ref name=":11">{{Cite book |last=Pérez-Crespo |first=J. Arroyo-Cabrales E. Johnson R.W. Graham V.A. |title=North American ursid (mammalia: ursidae) defaunation from Pleistocene to recent |date=2016-01-01 |oclc=1227719621}}</ref> However, despite ''Arctodus simus''<nowiki/>' large temporal and geographic range, fossil remains are comparatively rare (109 finds as of 2010, in otherwise well-sampled localities).<ref name=":0" /><ref name="Pedersen 2728–2736.e8">{{Cite journal|last1=Pedersen|first1=Mikkel Winther|last2=De Sanctis|first2=Bianca|last3=Saremi|first3=Nedda F.|last4=Sikora|first4=Martin|last5=Puckett|first5=Emily E.|last6=Gu|first6=Zhenquan|last7=Moon|first7=Katherine L.|last8=Kapp|first8=Joshua D.|last9=Vinner|first9=Lasse|last10=Vardanyan|first10=Zaruhi|last11=Ardelean|first11=Ciprian F.|date=2021-06-21|title=Environmental genomics of Late Pleistocene black bears and giant short-faced bears |journal=Current Biology |volume=31|issue=12|pages=2728–2736.e8|doi=10.1016/j.cub.2021.04.027|pmid=33878301|s2cid=233303447 |hdl=10037/22808|hdl-access=free}}</ref> This does not preclude genetic diversity in ''Arctodus'' however, with [[Mexico|Mexican]] genetic samples from [[Chiquihuite cave]] indicating a deep divergence with ''Arctodus'' finds from the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /> ==Description== === Size === [[File:ArctodusSimusReconstruct.jpg|thumb|''A. simus'' compared with a human]][[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus'']]Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|900|kg|ST|abbr=on|0}}, the largest from [[Salt Lake Valley]], [[Utah]] coming in at {{convert|957|kg|lb|abbr=on}}, suggesting specimens that big were probably more common than previously thought. However, half the specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957&nbsp;kg and 317&nbsp;kg, with an average weight of ~{{Convert|750|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_2010">{{cite journal |author=Figueirido |display-authors=etal |year=2010 |title=Demythologizing Arctodus simus, the 'short-faced' long-legged and predaceous bear that never was |journal=Journal of Vertebrate Paleontology |volume=30 |issue=1 |pages=262–275 |doi=10.1080/02724630903416027 |s2cid=85649497}}</ref> There is much variation in adult size among specimens- the paucity of finds, [[sexual dimorphism]] and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of ''Arctodus''.<ref>{{Cite journal |last1=Nelson |first1=Michael E. |last2=Madsen |first2=James H. |date=1983 |title=A Giant Short-Faced Bear (Arctodus simus) from the Pleistocene of Northern Utah |journal=Transactions of the Kansas Academy of Science |volume=86 |issue=1 |pages=1–9 |doi=10.2307/3628418 |jstor=3628418 }}</ref> The largest recorded individuals from the [[La Brea Tar Pits]] are much smaller than most specimens from [[Alaska]], [[Utah]] and [[Nebraska]]. This has been suggested as an [[Ecomorphology|ecomorphological]] difference (e.g. the La Brea specimens have a size variation of 25%, as could be expected with [[Bear|ursid]] [[sexual dimorphism]]), if not subspecies, with ''A. s. yukonensis'' inhabiting the northern and central portions of its range, and ''A. s. simus'' occurring elsewhere.<ref name="Figueiridio_et_al_2010" /> Once again, the low number of specimens and sex-biased sampling put doubt on this designation, in addition to a find of ''Arctodus simus'' well within the size range of ''A. s. yukonensis'' in [[Florida]], deep within the supposed range of ''A. s. simus''.<ref name=":0" /> Though over 100 giant short-faced bear localities in [[North America]] are known, only one site produced a [[baculum]] (penis bone) that could belong to ''Arctodus simus''. The lack of recovered ''Arctodus'' [[Baculum|bacula]] likely reflects both [[taphonomy]] and behaviour. The majority of skeletal remains representing large individuals are from open sites where usually only a few elements were recovered. In contrast, horizontal (walk-in) cave passages produced numerous examples of small, yet relatively complete individuals where [[Baculum|bacula]] would likely be found if they had been present. Both the small size of recovered skeletal elements and the lack of [[Baculum|bacula]] from cave deposits suggest that female individuals of ''A. simus'' were using caves, in line with [[Bear|ursid]] maternal denning.<ref name=":2">{{Cite journal|last1=CHUBERT|first1=BLAINE|last2=KAUFMANN|first2=JAMES|date=2003-08-01|title=A partial short-faced bear skeleton from an Ozark Cave with comments on the paleobiology of the species|url=https://www.researchgate.net/publication/252748398|journal=Journal of Cave and Karst Studies|volume=65}}</ref><ref name=":3">{{Cite journal|last1=Fowler|first1=Nicholas L.|last2=Spady|first2=Thomas J.|last3=Wang|first3=Guiming|last4=Leopold|first4=Bruce D.|last5=Belant|first5=Jerrold L.|date=October 2021|title=Denning, metabolic suppression, and the realisation of ecological opportunities in Ursidae |journal=Mammal Review |volume=51|issue=4|pages=465–481|doi=10.1111/mam.12246|s2cid=233847639 }}</ref> Therefore, in conjunction with ursid sexual dimorphism (e.g. in [[spectacled bear]]s, males are 30%-40% larger than females), the largest individuals are often considered male, particularly older males, with the smaller individuals being females.<ref name=":0" /><ref name=":12">{{Cite journal |last=Schubert |first=Blaine W. |date=2010-04-15 |title=Late Quaternary chronology and extinction of North American giant short-faced bears (Arctodus simus) |journal=Quaternary International |series=Faunal Dynamics and Extinction in the Quaternary: Studies in Honor of Ernest L. Lundelius, Jr. |volume=217 |issue=1 |pages=188–194 |doi=10.1016/j.quaint.2009.11.010 |bibcode=2010QuInt.217..188S }}</ref><ref name=":46">{{Cite journal |last=Scott |first=Eric |title=Arctodus simus (Cope, 1879) from Riverside County, California |url=https://www.academia.edu/1024642}}</ref> Standing up on the hind legs, ''Arctodus'' stood {{convert|8|-|10|ft|m|round=0.5|abbr=on|order=flip}}.<ref name="Simus" /> When walking on all fours, ''A. simus'' stood {{convert|5|-|6|ft|m|abbr=on|order=flip}} high at the shoulder and would be tall enough to look an adult human in the eye. The average weight of ''A. simus'' was ~{{Convert|750|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}. <ref name="Figueiridio_et_al_2010" /> Hypothetically, the largest individuals of ''A. simus'' may have approached {{Convert|1000|kg|lb}},<ref name=":7">{{Cite journal |last=Christiansen |first=Per |date=1999 |title=What size were Arctodus simus and Ursus spelaeus (Carnivora: Ursidae)? |journal=Annales Zoologici Fennici |volume=36 |issue=2 |pages=93–102 |jstor=23735739}}</ref> or even {{convert|1200|kg|lb|abbr=on}}.<ref name=":20">{{Cite journal|last1=SOIBELZON|first1=LEOPOLDO H.|last2=SCHUBERT|first2=BLAINE W.|title=The Largest Known Bear, Arctotherium Angustidens, from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears|date=2011 |journal=Journal of Paleontology|volume=85|issue=1|pages=69–75|doi=10.1666/10-037.1|jstor=23019499|s2cid=129585554 }}</ref> However, a 2006 study argued that based on the dimensions of the axial skeleton of the ''Arctodus'' individual with the largest known skull, the maximum size of that ''Arctodus'' was ~555kg.<ref name=":1" /> Additionally, a 1994 study calculated the average weight of ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]] at ~372kg, smaller than recovered [[brown bear]] remains (~455kg, although these remains may postdate ''Arctodus'').<ref name=":34">{{Cite journal |last1=Lambert |first1=W. David |last2=Holling |first2=Crawford S. |date=1998-03-01 |title=Original Articles: Causes of Ecosystem Transformation at the End of the Pleistocene: Evidence from Mammal Body-Mass Distributions |url=http://link.springer.com/10.1007/s100219900012 |journal=Ecosystems |volume=1 |issue=2 |pages=157–175 |doi=10.1007/s100219900012 |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":36">{{Cite journal |last=Kurten |first=B. |last2=Anderson |first2=Elaine |date=1974 |title=Association of Ursus arctos and Arctodus simus (Mammalia: Ursidae) in the late Pleistocene of Wyoming |url=https://www.biodiversitylibrary.org/part/32631 |journal=Breviora |volume=426 |pages=1––6 |issn=0006-9698}}</ref><ref>{{Cite web |title=The California grizzly bear {{!}} La Brea Tar Pits |url=https://tarpits.org/california-grizzly-bear |access-date=2022-06-22 |website=tarpits.org |language=en}}</ref> A 1999 study by Christiansen calculated a mean weight of ~770kg from six specimens.<ref name=":7" /> Regardless, at [[Riverbluff Cave]], [[Missouri]], a series of claw marks up to {{convert|15|ft|m|abbr=on|order=flip}} high have been found along the cave wall, indicating that some ''A. simus'' could have stood up to {{convert|12|ft|m|abbr=on|order=flip}} tall.<ref>{{cite web|title=Bear Claw Marks|url=http://www.riverbluffcave.com/gallery/rec_id/104/type/1|work=Riverbluff Cave - The Official Website|access-date=17 April 2014}}</ref><ref>{{cite web|title=Cave Animals|url=http://www.riverbluffcave.com/category/cave_animals|work=Riverbluff Cave - The Official Website|access-date=17 April 2014}}</ref> Both [[Tremarctinae|giant short faced bears]] ''Arctodus simus'' and ''[[Arctotherium|Arctotherium angustidens]]'' reached huge body sizes, in an example of [[convergent evolution]].<ref name=":28" /> However, beyond gigantism, there are notable differences between the species. Not only did ''Arctotherium angustidens'' reach a higher maximum weight (an exceptional specimen was calculated at ~{{Convert|1670|kg|lb}}), ''A. angustidens'' was a much more [[Robustness (morphology)|robust]] animal, in contrast with the [[Gracility|gracile]] ''Arctodus simus''.<ref name=":20" /> Excluding the exceptional specimen, ''Arctotherium angustidens'' had been calculated to a weight range between 1,200 kg and 412kg,<ref name=":32">{{Cite journal |last1=Soibelzon |first1=Leopoldo |last2=Tarantini |first2=Viviana Beatriz |date=January 2009 |title=Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae) |url=https://www.researchgate.net/publication/279714500 |journal=Revista del Museo Argentino de Ciencias Naturales |volume=11 |issue=2 |pages=243–254 |doi=10.22179/REVMACN.11.263 |via=ResearchGate}}</ref> whereas ''Arctodus simus'' was calculated to a weight range between 957 kg (~1,000kg) and 317 kg.<ref name="Figueiridio_et_al_2010" /> Within these ranges, the largest specimens of both species are said to be comparable to one another.<ref name=":32" /><ref name=":30" /> === Data === Below is a table comparing the dimensions of several adult ''Arctodus simus'' [[Femur|femora]], including one of the largest on record from [[Salt Lake Valley]], [[Utah]], from a 1994 study.<ref>{{Cite journal |last=Burns |first=James A. |last2=Young |first2=Robert R. |date=1994-02-01 |title=Pleistocene mammals of the Edmonton area, Alberta. Part I. The carnivores |url=http://www.nrcresearchpress.com/doi/10.1139/e94-036 |journal=Canadian Journal of Earth Sciences |language=en |volume=31 |issue=2 |pages=393–400 |doi=10.1139/e94-036 |issn=0008-4077}}</ref> Also included are the mean figures from [[Björn Kurtén|Björn Kurtén's]] seminal 1967 study.<ref>{{Cite book |last=Kurtén |first=Björn |url=https://www.worldcat.org/title/pleistocene-bears-of-north-america-2-genus-arctodus-short-faced-bears/oclc/312819421 |title=Pleistocene bears of North America 2, 2, |date=1967 |publisher=Societas pro Fauna et Flora Fennica |location=Helsinki |language=English |oclc=312819421}}</ref> {| class="wikitable" |+ !Element ID & Location !Proximal Length (mm) !Total Length (mm) !Transverse Width (midshaft, mm) !Ratio of TL to TW (M) x 100 !Standard Deviation !Number |- |P.89.13.91, [[Edmonton]] |585 |707 (est.) |63.2 |9.0 |~ |1 |- |UVP 015/1, Utah |598 |723 |64 |8.9 |~ |1 |- |LACMNH-Z75, [[La Brea Tar Pits|Rancho La Brea]] |444 |~ |42.3 |~ |~ |1 |- |U.S.A. sites, x̄ values (Kurtén, 1967) |~ |584 |47.8 |8.1-9.5 (x̄= 8.7) |0.45 |9 |} === Anatomy === [[File:Arctodus simus skull Cleveland.jpg|thumb|''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], [[Ohio]]]]Members of the [[Tremarctinae]] subfamily of [[bear]]s appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced." This apparent shortness is an illusion caused by the deep snouts and short nasal bones of [[Tremarctinae|tremarctine]] bears compared with [[Ursinae|ursine]] bears; ''Arctodus'' has a deeper but not a shorter face than most living bears. This characteristic is also shared by the only living tremarctine bear, the [[spectacled bear]].<ref name="Figueiridio_et_al_2010" /><ref name=":30" /> The skull also has a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance; this broad [[snout]] possibly housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas (although this is characteristic shared with the omni-herbivorous [[spectacled bear]]).<ref name=":7" /><ref name=":13" /><ref name=":40">{{Cite journal |last=Matheus |first=Paul E. |date=1995-11-01 |title=Diet and Co-ecology of Pleistocene Short-Faced Bears and Brown Bears in Eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0033589485710903 |journal=Quaternary Research |language=en |volume=44 |issue=3 |pages=447–453 |doi=10.1006/qres.1995.1090 |issn=0033-5894}}</ref> The [[Orbit (anatomy)|orbits]] of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat [[Lateral (anatomy)|laterally orientated]] (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the [[brown bear]], suggesting that [[Stereopsis|stereoscopic vision]] was not a priority.<ref name=":1" /><ref name=":30" /><ref name=":29">{{Cite book |last=Baryshnikov |first=Gennady |url=https://www.researchgate.net/publication/336916777 |title=The Hot Springs Mammoth Site: A Decade of Field and Laboratory Research in Paleontology, Geology and Paleoecology |publisher=The Mammoth Site of Hot Springs, South Dakota Inc. |year=1994 |editor-last=Agenbroad |editor-first=Larry D. |pages=Chapter 16 |editor-last2=Mead |editor-first2=Jim I.}}</ref> The [[Premolar|premolars]] and [[Molar (tooth)|first molars]] of ''Arctodus pristinus'' are relatively smaller and more widely spaced than those of ''Arctodus simus''. However, the morphologies of both species are otherwise very similar. Differentiating between the two can be difficult, as males of ''A. pristinus'' overlap in size with females of ''A. simus''.<ref name=":26" /><ref name=":0" /> The dentition of ''Arctodus'' has been used as evidence of a predatory lifestyle- in particular the large [[Canine tooth|canines]], the high-crowned lower [[first molar]], and the possible [[carnassial shear]] with the upper [[Premolar|fourth premolar]]. However, the wearing of the molars to a relatively flat, blunt loph (suitable as a crushing platform as per modern omnivorous bears), small shear facet, and the flattened [[Cusp (anatomy)|cusps]] across age ranges (unlike carnivores, which instead have [[Carnassial shear|carnassial shears]]) suggests an alternative adaptive purpose.<ref name=":13" /> An analysis of the [[Mandible|mandibular]] morphology of tremarctine bears found that ''Arctodus pristinus'' and ''Arctodus simus'' were divergent in the dimensions of their cranial anatomy, with ''Arctodus simus'' clustering tightly with ''Arctotherium angustidens'', suggesting a similar foraging strategy. ''A. simus'' specimens have a concave jaw, large [[Masseter muscle|masseter]] and [[Temporalis muscle|temporalis]] muscles, deeper horizontal ramus and a reduced slicing dentition length, which relate more to ''A. pristinus''. However, both ''A. pristinus'' and ''A. simus'' were still found to be comfortably in the "omnivorous" bear cranio-morphotype, and are interpreted as such, along with ''Arctotherium angustidens''.<ref name=":30" /> Although the shape of the [[Elbow|elbow joint]] suggests ''Arctodus'', ''[[Arctotherium|Arctotherium bonariense]]'', and ''[[Arctotherium|Arctotherium wingei]]'' had the possibility of retaining [[Arboreal locomotion|semi-arboreal]] adaptations, the size of the elbow joint condemns ''Arctodus'' to terrestrial life. As the [[Medial epicondyle of the humerus|medial epicondyle]] is particularly expanded in these species, it is likely that ''Arctodus'' and ''Arctotherium'' (just like the [[giant panda]]) retained this characteristic to attain a higher degree of forelimb dexterity. Whether this dexterity facilitated [[Scavenger|scavenging]] or [[Herbivore|herbivory]], this high degree of proximal dexterity was probably advantageous for these species, and retained in tremarctine bears despite their general tendency towards terrestriality.<ref name=":28">{{Cite journal|last1=Mitchell|first1=Kieren J.|last2=Bray|first2=Sarah C.|last3=Bover|first3=Pere|last4=Soibelzon|first4=Leopoldo|last5=Schubert|first5=Blaine W.|last6=Prevosti|first6=Francisco|last7=Prieto|first7=Alfredo|last8=Martin|first8=Fabiana|last9=Austin|first9=Jeremy J.|last10=Cooper|first10=Alan|date=2016-04-30|title=Ancient mitochondrial DNA reveals convergent evolution of giant short-faced bears (Tremarctinae) in North and South America|journal=Biology Letters|volume=12|issue=4|pages=20160062|doi=10.1098/rsbl.2016.0062|pmc=4881349|pmid=27095265}}</ref><ref name=":13" /><ref name="Meloro 133–146">{{Cite journal|last1=Meloro|first1=Carlo|last2=de Oliveira|first2=Alessandro Marques|date=2019-03-01|title=Elbow Joint Geometry in Bears (Ursidae, Carnivora): a Tool to Infer Paleobiology and Functional Adaptations of Quaternary Fossils |journal=Journal of Mammalian Evolution |volume=26|issue=1|pages=133–146|doi=10.1007/s10914-017-9413-x|s2cid=25839635 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf}}</ref> A 2010 study found that its legs weren't proportionally longer than modern bears would be expected to have, and that bears in general being long-limbed animals is obscured in life by their girth and fur. The study concluded the supposed "long-legged" appearance of the bear is largely an illusion created by the animal's relatively shorter back and torso- proportions today shared with [[hyena]]s.<ref name="Figueiridio_et_al_2010" /><ref name=":1" /> The [[Paw|paws]] ([[Metapodial|metapodials]] and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and forth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''’ paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the first digit ([[Toe|hallux]]) of ''Arctodus'' was positioned more closely and parallel to the other four digits (i.e. with straight toes, ''Arctodus'' had less lateral splaying).<ref name=":27">{{Cite thesis |title=Paleoecology and ecomorphology of the giant short-faced bear in Eastern Beringia |url=https://scholarworks.alaska.edu/handle/11122/9491 |date=1997 |degree=Thesis |language=en |first=Paul Edward |last=Matheus}}</ref> This theory is potentially contradicted by trackways tentatively attributed to ''Arctodus'' from near [[Lakeview, Oregon|Lakeview]] in [[Oregon]]. The trackways, which fit the dimensions of ''Arctodus simus''<nowiki/>' paws, exhibit extreme toe splaying, with three centrally aligned, evenly spaced toes at the front, and two backward facing toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had a oval-shaped, undivided pad on its sole (with no toe pad impressions), with front paws that were slightly larger than its back paws, possessed long claws, and had its hind foot overstep the forefoot when walking, like modern bears.<ref>{{Cite web |last1=Packard |first1=E.L. |last2=Allison |first2=I.S. |last3=Cressman |first3=L.S. |title=Mammalian Tracks in the Late Pliocene or Early Pleistocene Beds of Lake County Oregon |url=https://www.oregongeology.org/milo/archive/MiningDistricts/LakeCounty/UnclassifiedDistrict/LakeCountyFossilLocalities/LakeCountyFossilLocalitiesReports.pdf |access-date=June 11, 2017 |website=Oregon Geology}}</ref> The presence of a partial [[Sesamoid bone#Other animals|false thumb]] in ''Arctodus simus'' is a characteristic shared with ''[[Tremarctos floridanus]]'' and the [[spectacled bear]], and is possibly an [[Plesiomorphy and symplesiomorphy|ancestral]] trait. Absent in [[Ursinae|ursines]], the false thumb of the spectacled bear has been suggested to assist in herbivorous food manipulation, or [[arboreality]].<ref>{{Cite journal |last=Salesa |first=M. J. |last2=Siliceo |first2=G. |last3=Antón |first3=M. |last4=Abella |first4=J. |last5=Montoya |first5=P. |last6=Morales |first6=J. |date=2006-12-30 |title=Anatomy of the "false thumb" of Tremarctos ornatus (Carnivora, Ursidae, Tremarctinae): Phylogenetic and functional implications |url=http://estudiosgeol.revistas.csic.es/index.php/estudiosgeol/article/view/33/32 |journal=Estudios Geológicos |volume=62 |issue=1 |pages=389–394 |doi=10.3989/egeol.0662133 |issn=1988-3250}}</ref> Examinations on a young individual of ''Arctodus simus'' from an [[Ozarks|Ozark]] cave suggest that ''Arctodus'', like other [[Bear|ursids]], reached [[sexual maturity]] before [[Bone age|osteological maturity]]. Comparisons with known [[Epiphyseal plate|epiphyseal fusion sequences]] in [[American black bear|''Ursus americanus'']] demonstrated that while the individual was not osteologically mature when it died (numerous [[Epiphysis|epiphyses]] were unfused) the stage of fusion of the [[long bone]] [[Epiphyseal plate|epiphyseal plates]] indicated that the specimen was mostly full sized, and was therefore sexually mature well before such fusions are complete. If ''Arctodus'' were similar in their timing of sexual maturity to modern ''Ursus americanus'', then the ''Arctodus'' specimen was already sexually mature, and was either 4-6 years of age if female, or 6-8 years if the specimen was male. Additionally, wear patterns on the individual's teeth are similar to a 4-6 year old ''Ursus americanus''. For comparison, female [[Spectacled bear|''Tremarctos ornatus'']] reach sexual maturity ~4 years of age, female [[American black bear|''Ursus americanus'']] become sexually mature between 2-4 years of age, and female [[Brown bear|''Ursus arctos'']] begin breeding in some portions of their range at around 3 years.<ref name=":2" /> ==Paleobiology== === ''Arctodus pristinus'' === [[File:American mastodon with calf.jpg|thumb|222x222px|''Arctodus'' may have found young [[Proboscidea|proboscideans]] to be suitable prey.]] The bite marks found on many bones of [[Ground sloth|sloths]] and young [[proboscidea]]ns at [[Cockroach Bay Aquatic Preserve|Leisey Shell Pit]] in [[Florida]] matched the size of the canine teeth of ''Arctodus pristinus''. It is not known if these bite marks are the result of active predation or scavenging.<ref name=":26">{{Cite web|date=2017-03-30|title=Arctodus pristinus|url=https://www.floridamuseum.ufl.edu/florida-vertebrate-fossils/species/arctodus-pristinus/|access-date=2022-02-21|website=Florida Museum|language=en-US}}</ref> In the [[Gelasian|Early Pleistocene]] of [[Blancan]] [[Florida]], the [[Santa Fe River (Florida)|Santa Fe River 1 site]] (2.2-1.8 Ma), which ''Arctodus pristinus inabited'', indicated a fairly [[Savanna|open grassland]] environment. [[Karst|Karst sinks]] and [[Spring (hydrology)|springs]] were present, very much like modern [[Florida]]. ''Arctodus pristinus'' would have co-existed with megafauna such as terror birds (''[[Titanis]])'', sabertooth cats (''[[Xenosmilus]]''), giant sloth (''[[Eremotherium]]'', ''[[Glossotherium]]'', ''[[Megalonyx]]''), giant armadillos (''[[Holmesina]]'', ''[[Glyptotherium]]''), [[gomphothere]]s (''[[Rhynchotherium]]'' (''[[Cuvieronius|?Cuvieronius?]]'')), hyenas (''[[Chasmaporthetes|Chasmoporthetes]]''), canids (''[[Borophagus]]'', ''[[Canis lepophagus]]''), peccary (''[[Platygonus]]''), llama (''[[Hemiauchenia]]''), antilocaprids (''[[Capromeryx]]''), and three-toed horse (''[[Nannippus]]''). Smaller fauna included [[condor]]s, [[Rail (bird)|rails]] and [[duck]]s among other small birds, [[rodent]]s such as [[Erethizon|porcupines]], [[lizard]]s, [[snake]]s, [[alligator]]s, [[turtle]]s, and [[arthropod]]s.<ref>{{Cite journal |last1=Gould |first1=G.C. |last2=Quitmyer |first2=Irvy |date=2005-01-01 |title=Titanis walleri: Bones of contention |url=https://www.researchgate.net/publication/288892560 |journal=Bulletin of the Florida Museum of Natural History |volume=45 |pages=201–229}}</ref><ref>{{Cite journal |last1=MacFadden |first1=Bruce |last2=Labs-Hochstein |first2=Joann |last3=Hulbert |first3=Richard |last4=Baskin |first4=Jon |date=2007-02-01 |title=Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange |url=https://www.researchgate.net/publication/249521166 |journal=Geology |volume=35 |issue=2 |page=123 |doi=10.1130/G23186A.1|bibcode=2007Geo....35..123M }}</ref> The evolution of ''Arctodus simus'', competition with ''[[Tremarctos floridanus]]'' and [[American black bear|black bears]] (which only appear in [[Florida]] in the [[Late Pleistocene]]),<ref name=":5"/> and possibly the transitioning of [[Pleistocene]] [[Florida]] from a hot, wet, densely forested habitat to a still hot, but drier and much more open biome are thought to be factors behind the gradual disappearance of ''Arctodus pristinus'' in the [[Chibanian|Middle Pleistocene]] (300,000 BP).<ref name=":0" /><ref name=":9" /> ''Arctodus pristinus'' has also been found in [[Kansas]], [[South Carolina]], [[Maryland]], [[Pennsylvania]], and [[New Jersey]] in the [[United States|US]], and [[Aguascalientes]] in [[Mexico]].<ref name=":5" /><ref name=":6" /><ref name=":8" /> === ''Arctodus simus'' === ==== Paleoecology ==== [[File:Camino a paso de Cortès. - panoramio.jpg|thumb|238x238px|[[Woodland|Open woodlands]], such as those in the [[Trans-Mexican Volcanic Belt|Mexican highlands]], would have presented ample foraging opportunities for ''Arctodus''. ]] Evolving from the smaller ''A. pristinus'' around 800,000 years ago, scholars today mostly conclude that ''Arctodus simus'' was a colossal, opportunistic [[omnivore]], with a flexible, locally adapted diet akin to the [[brown bear]].<ref name="Figueiridio_et_al_2010" /><ref>{{Cite book|last=Nowak, Ronald M.|title=Walker's mammals of the world|date=1999|publisher=Johns Hopkins University Press|isbn=0-8018-5789-9|edition=Sixth|location=Baltimore|oclc=39045218}}</ref><ref name=":30">{{Cite journal |last1=FIGUEIRIDO |first1=BORJA |last2=SOIBELZON |first2=LEOPOLDO H. |date=2009-08-19 |title=Inferring palaeoecology in extinct tremarctine bears (Carnivora, Ursidae) using geometric morphometrics |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x |url=http://sedici.unlp.edu.ar/handle/10915/5372 }}</ref><ref name=":15">{{Cite journal |last1=Steffen |first1=Martina L. |last2=Fulton |first2=Tara L. |date=2018-02-01 |title=On the association of giant short-faced bear (Arctodus simus) and brown bear (Ursus arctos) in late Pleistocene North America |journal=Geobios |volume=51 |issue=1 |pages=61–74 |doi=10.1016/j.geobios.2017.12.001 }}</ref> If ''Arctodus simus'' wasn't largely herbivorous,<ref name=":5" /><ref name=":13">{{Cite journal |last1=Emslie |first1=Steven D. |last2=Czaplewski |first2=Nicholas J. |date=1985-11-15 |title=A new record of giant short-faced bear, Arctodus simus, from western North America with a re-evaluation of its paleobiology |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793 |url=https://www.biodiversitylibrary.org/partpdf/226835 }}</ref> the scavenging of [[megaherbivore]] carcasses, and the occasional predatory kill would have complimented the large amounts of vegetation consumed when available.<ref name="Figueiridio_et_al_2010" /><ref name=":1">{{cite journal |last1=Sorkin |first1=B. |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |date=January 2006 |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |s2cid=85301983 }}</ref> [[Carbon-13]] ([[Δ13C|''δ''¹³C]]) isotope data gathered from ''Arctodus'' specimens from [[Beringia]], [[California]] and [[Mexico]], indicates that ''Arctodus simus'' had a diet based on [[C3 carbon fixation|C3 resources]]. Preferring closed habitat ([[Woodland|open woodland]] & [[forest]]), ''Arctodus'' either consumed [[C3 carbon fixation|C3 vegetation]] ([[Leaf|leaves]], [[Plant stem|stems]], [[fruit]]s, [[Bark (botany)|bark]], and [[flower]]s from trees, shrubs, and cool season [[Poaceae|grasses]]) or the browsers that fed on them, such as [[deer]], [[Camelidae|camelids]], [[Tapirus|tapir]], [[bison]] and [[ground sloth]]s.<ref name="Figueiridio_et_al_2010" /><ref name=":23">{{Cite journal |last=Trayler |first=Robin B. |last2=Dundas |first2=Robert G. |last3=Fox-Dobbs |first3=Kena |last4=Van De Water |first4=Peter K. |date=2015-11-01 |title=Inland California during the Pleistocene—Megafaunal stable isotope records reveal new paleoecological and paleoenvironmental insights |url=https://www.sciencedirect.com/science/article/pii/S0031018215004010 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=437 |pages=132–140 |doi=10.1016/j.palaeo.2015.07.034 |issn=0031-0182}}</ref> ''Arctodus simus'' was particularly plentiful in western [[North America]]- however, in relation to the comparatively small number of finds in relation to other large carnivorans, ''Arctodus'' is suggested to have lived in low population densities.<ref name="Pedersen 2728–2736.e8" /> Typically thought of as an open habitat specialist, ''Arctodus'' seems to have also been abundant in mixed habitat where [[C3 carbon fixation|C3 vegetation]] was available. Based on the wide distribution of the species, ''Arctodus simus'' inhabited diverse climatic conditions and all sorts of environments, ranging from [[Taiga|boreal forests]] and [[mammoth steppe]] in the north, [[Grassland|open plains]] and [[Montane ecosystems|highland woodlands]] in the interior, [[Subtropics|subtropical]] [[woodland]]s and [[savanna]]s in the south, to the [[Trans-Mexican Volcanic Belt pine–oak forests|pine–oak forests]] of the [[Trans-Mexican Volcanic Belt]], the boundary of the [[Nearctic realm]].<ref name=":35" /><ref name=":0" /><ref name=":10" /><ref name=":13" /><ref name=":4">{{Cite journal|last1=Pérez-Crespo|first1=Víctor Adrián|last2=Arroyo-Cabrales|first2=Joaquín|last3=Morales-Puente|first3=Pedro|last4=Cienfuegos-Alvarado|first4=Edith|last5=Otero|first5=Francisco J.|date=March 2018|title=Diet and habitat of mesomammals and megamammals from Cedral, San Luis Potosí, México |journal=Geological Magazine |volume=155|issue=3|pages=674–684|doi=10.1017/S0016756816000935|bibcode=2018GeoM..155..674P|s2cid=132502543 }}</ref><ref name=":37">{{Cite journal |last=Eng-Ponce |first=Joaquin |date=August 2021 |title=Reconstruccion paeloambiental del yacimiento La Cinta-Portalitos, Michoacan-Guanajuato, Mexico (thesis) |url=http://bibliotecavirtual.dgb.umich.mx:8083/xmlui/bitstream/handle/DGB_UMICH/6432/FB-M-2021-0909.pdf |journal=Faculty of Biology, Universidad Michoacana de San Nicolás de Hidalgo}}</ref> Throughout the temporal and geographic range of ''Arctodus simus'', the species would have co-existed with various large carnivores and omnivores, such as [[Dire wolf|dire wolves]], ''[[Smilodon]]'', ''[[Homotherium]]'', [[Cougar|puma]], [[dhole]]s, [[Coyote|coyotes]], [[Wolf|grey wolves]], [[Panthera onca augusta|jaguars]], [[American cheetah]]s, [[American lion]]s, [[Beringia|Beringian]] [[Panthera spelaea|cave lions]], and other [[bear]]s, such as the [[American black bear|black bear]], [[Tremarctos floridanus|Florida short-faced bear]], and the [[brown bear]]. The assemblage of [[Quaternary extinction|megafaunal herbivores]] in [[Pleistocene]] [[North America]] would have included [[proboscidea]]ns (the [[woolly mammoth]] in the north, ''[[Stegomastodon]], [[Cuvieronius]]'' and the [[Columbian mammoth|Colombian mammoth]] the south, and [[mastodon]] throughout), camelids (''[[Camelops]], [[Hemiauchenia macrocephala|Hemiauchenia]], [[Palaeolama]]''), horses (''[[Equus (genus)|Equus]],'' ''[[Haringtonhippus|Harringtonhippus]]''), giant armadillos (''[[Glyptotherium]],'' ''[[Pachyarmatherium]]'', ''[[Pampatherium]]'', ''[[Holmesina]]''), [[Tapirus|tapirs]], ground sloths (''[[Eremotherium]]'', ''[[Nothrotheriops]], [[Paramylodon]], [[Megalonyx]]''), [[bison]], notoungulates (''[[Mixotoxodon]]''), deer ([[Moose|''Alces'']], [[Cervalces scotti|''Cervalces'']], ''[[Elk|Cervus]]'', ''[[Odocoileus]]'', ''[[Reindeer|Rangifer]]''), [[Caprinae|oxen]] (''[[Muskox|Ovibos]]'', ''[[Bootherium]]'', ''[[Euceratherium]]'', ''[[Soergelia]]''), [[giant anteater]], various [[Antilocapridae|antilocaprids]], [[Neochoerus pinckneyi|capybara]], [[Peccary|peccaries]], [[saiga antelope]], and the [[Castoroides|giant beaver]].<ref name=":44">{{Cite journal |last=Stuart |first=Anthony John |date=May 2015 |title=Late Quaternary megafaunal extinctions on the continents: a short review: LATE QUATERNARY MEGAFAUNAL EXTINCTIONS |url=https://onlinelibrary.wiley.com/doi/10.1002/gj.2633 |journal=Geological Journal |language=en |volume=50 |issue=3 |pages=338–363 |doi=10.1002/gj.2633}}</ref><ref>{{Citation |last=David Webb |first=S. |title=Vertebrate paleontology |date=2003 |url=https://linkinghub.elsevier.com/retrieve/pii/S157108660301025X |work=Developments in Quaternary Sciences |volume=1 |pages=519–538 |publisher=Elsevier |language=en |doi=10.1016/s1571-0866(03)01025-x |isbn=978-0-444-51470-7 |access-date=2022-06-28 |last2=Graham |first2=Russell W. |last3=Barnosky |first3=Anthony D. |last4=Bell |first4=Christopher J. |last5=Franz |first5=Richard |last6=Hadly |first6=Elizabeth A. |last7=Lundelius |first7=Ernest L. |last8=Gregory McDonald |first8=H. |last9=Martin |first9=Robert A.}}</ref> A possible record of an indeterminate [[Litopterna|litoptern]] has also been noted from [[Mexico City|México City]].<ref name=":35" /><ref>{{Cite journal |last=Ferrusquía-Villafranca |first=Ismael |last2=Malvido-Arriaga |first2=Roberto |date=September 2006 |title=A possible record of the South American mammal order Litopterna in Mexico |url=https://www.researchgate.net/publication/296343425_A_possible_record_of_the_South_American_mammal_order_Litopterna_in_Mexico |journal=Journal of Vertebrate Paleontology |volume=26 |issue=3 |pages=60-61 |via=ResearchGate}}</ref> Preliminary data suggests that certain habitat was optimal for ''Arctodus simus'' populations- the [[pluvial lake]]s, [[montane forests]] and [[Shrub–steppe|arid sagebrush steppe/grassy plains]] of the inland western USA,<ref>{{Cite journal |last=Grayson |first=Donald K. |date=2006-11-01 |title=The Late Quaternary biogeographic histories of some Great Basin mammals (western USA) |url=https://www.sciencedirect.com/science/article/pii/S0277379106001405 |journal=Quaternary Science Reviews |language=en |volume=25 |issue=21 |pages=2964–2991 |doi=10.1016/j.quascirev.2006.03.004 |issn=0277-3791}}</ref> the [[Montane ecosystems|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], [[Paludification|paludified]] [[mammoth steppe]] in [[Beringia]], and the [[Savanna|mixed savannas]] of the [[Basin and Range Province|south-western USA]] and [[Mexican Plateau]].<ref name=":9" /><ref name=":19" /><ref name=":14">{{Cite journal |last1=Figueirido |first1=Borja |last2=Perez |first2=Alejandro |last3=Schubert |first3=Blaine |last4=Serrano |first4=Francisco |last5=Farrell |first5=Aisling |last6=Pastor |first6=Francisco |last7=Neves |first7=Aline |last8=Romero |first8=Alejandro |date=2017-12-19 |title=Dental caries in the fossil record: A window to the evolution of dietary plasticity in an extinct bear |url=https://www.researchgate.net/publication/321791811 |journal=Scientific Reports |volume=7 |issue=1 |page=17813 |doi=10.1038/s41598-017-18116-0|pmid=29259277 |pmc=5736623 |bibcode=2017NatSR...717813F }}</ref> ==== Opportunistic carnivory ==== [[File:Smilodon gaping.jpg|thumb|The enormous canines of sabertooth cats such as ''[[Smilodon]]'' would have made carcass consumption difficult, presenting a scavenging opportunity for ''Arctodus''.]]Although evidence suggests that ''Arctodus'' consumed meat, studies suggest that isotope data cannot differentiate between hypercarnivores and omnivores which consume significant amounts of animal matter.<ref name=":1" /> Evidence from the [[Δ13C|carbon isotope]] values of an ''Arctodus simus'' individual from [[Cedral, San Luis Potosí|Cedral]], [[San Luis Potosí]], [[Mexico|México]], suggested that ''Arctodus simus'' from this locality preferred areas of closed vegetation. Owing to having only one sample of ''Arctodus simus'' from [[Cedral, San Luis Potosí|Cedral]] and the lack of nitrogen isotopic values, the study found it difficult to infer whether ''Arctodus simus'' was an [[omnivore]] or [[hypercarnivore]]. The [[Δ13C|''δ''¹³C]] value, however, showed that this individual fed upon [[C3 carbon fixation|C3]] herbivores, ([[C3 carbon fixation|C3]] vegetative consumption by ''Arctodus'' itself notwithstanding) which were different from those eaten by the open habitat-specialized [[American lion]] and the [[dire wolf]]. ''Arctodus''<nowiki/>' [[Carbon-13|carbon isotope]] value did not overlap with, but was closest to values from the [[tapir]] and ''[[Hemiauchenia]]''. Those animals could have been included in their diet, along with other contemporaneous [[C3 carbon fixation|C3]] herbivores such as [[Camelops|camels]], [[Platygonus|peccaries]], ''[[Nothrotheriops]]'' and [[mastodon]]. The site hosted a [[gallery forest]] near to [[Savanna|grassland]] or [[Shrubland|scrub]], with a [[Humid subtropical climate|humid climate]]. This [[Savanna|forest-savanna mosaic]], supporting a diverse mammalian herbivore and carnivore fauna, was part of the wider [[Mesic habitat|mesic]] savanna ecoregion which ''Arctodus'' inhabited in the [[Late Pleistocene]] [[Mexican Plateau|central Mexico]] and [[Southwestern United States|southwestern USA]].<ref name=":4" /><ref name=":37" /><ref>{{Cite book |last=Harris |first=Arthur |url=https://www.researchgate.net/publication/265165536 |title=Pleistocene Vertebrates of Southwestern USA and Northwestern Mexico |date=2014-08-30}}</ref><ref>{{Cite journal |last=Harris |first=Arthur H. |title=Reconstruction of Mid Wisconsin Environments in Southern New Mexico |url=https://www.wipp.energy.gov/library/cra/2009_cra/references/Others/Harris_1987_Reconstruction_of_Mid_Wisconsin_Environments.pdf |journal=National Geographic Research}}</ref> A likely faunal interaction was between ''[[Smilodon]]'' and ''Arctodus''- the sabretooth cat's theorized inability to consume all but the soft tissue of their kills would leave large portions of the carcass available to scavengers such as ''Arctodus''. ''Arctodus''<nowiki/>' scavenging had the potential to be [[Kleptoparasitism|kleptoparasitic]]- however, in addition to many contemporaneous predators being [[Sociality|gregarious]] and thus better able to defend their kills, ''Arctodus''<nowiki/>' great size variation would have likely limited the frequency of this behavior to all but the largest ''Arctodus simus''.<ref name="Figueiridio_et_al_2010" /> For specimens from inland [[California]] ([[Madera County, California|Fairmead Landfill]]) from the [[Irvingtonian|Middle Pleistocene]], a 2012 study proposed that ''Arctodus simus'' consumed Colombian mammoth, and large [[Ungulate|ungulates]]- that ''Arctodus'' likely consumed substantial amounts of vegetation made conclusive determinations unclear.<ref>{{Cite journal |last=Trayler |first=Robin Brendan |date=December 2012 |title=Stable Isotope Records of Inland California Megafauna- New Insights Into Pleistocene Paleoecology and Paleoenvironmental Conditions (Masters Thesis) |url=https://scholarworks.calstate.edu/downloads/h128nf901 |journal=College of Science and Mathematics, California State University Fresno}}</ref> However, the author republished in 2015 with colleagues, recalibrating ''Arctodus''<nowiki/>' [[Δ13C|''δ''¹³C]] values to be closest to [[C3 carbon fixation|C3 vegetation]] consuming ''[[Cervus]]'' and ''[[Mastodon|Mammut]]'', if the consumption of C3 vegetation by ''Arctodus'' is not included.<ref name=":23" /> In the later Californian [[McKittrick Tar Pits]], ''Arctodus simus'' had a diet which included [[deer]] and [[tapir]], similar to the one inferred for the [[Cedral, San Luis Potosí|Cedral]] individual.<ref name=":4" /> [[Alaska|Alaskan]] specimens were thought to also largely predate upon similar megafauna as proposed for the Fairmead individuals in the 2012 study,<ref name=":27" /> but isotope data suggests [[reindeer]], [[muskox]] and possibly fellow predators and their kills, were regularly consumed.<ref name=":31">{{Cite journal |last=Bocherens |first=Hervé |date=2015-06-01 |title=Isotopic tracking of large carnivore palaeoecology in the mammoth steppe |url=https://www.sciencedirect.com/science/article/pii/S0277379115001250 |journal=Quaternary Science Reviews |language=en |volume=117 |pages=42–71 |doi=10.1016/j.quascirev.2015.03.018 |issn=0277-3791}}</ref> A single find from the [[Channel Islands (California)|Channel Islands]] of [[California]] replete with nitrogen isotope signatures aligning with [[bison]] and [[Camelidae|camels]] (followed by [[pinniped]]s) bolsters the suggestion that although not entirely carnivorous, ''A. simus'' would have had a flexible diet across its range. That the ''Arctodus'' fossil in the [[Channel Islands (California)|Channel Islands]] was likely transported post-mortem from the [[California|North American mainland]] further complicates the idea of a standard diet for ''Arctodus,'' as the mainland would have had plenty of vegetation to consume.<ref name=":47">{{Cite journal |last1=Mychajliw |first1=Alexis M. |last2=Rick |first2=Torben C. |last3=Dagtas |first3=Nihan D. |last4=Erlandson |first4=Jon M. |last5=Culleton |first5=Brendan J. |last6=Kennett |first6=Douglas J. |last7=Buckley |first7=Michael |last8=Hofman |first8=Courtney A. |date=2020-09-16 |title=Biogeographic problem-solving reveals the Late Pleistocene translocation of a short-faced bear to the California Channel Islands |journal=Scientific Reports |volume=10 |issue=1 |pages=15172 |doi=10.1038/s41598-020-71572-z |pmid=32938967 |pmc=7494929 }}</ref> Bone damage on a [[Cranium|cranial fragment]] (and possibly the humerus) of an ''Arctodus'' individual in a cave on [[Vancouver Island]] has been attributed to another ''Arctodus'', on the basis that ''Arctodus'' was the only confirmed large terrestrial [[Carnivora|carnivoran]] there at the time.<ref name=":15" /> ''Arctodus'' has been found in association with [[Proboscidea|proboscidean]] remains near [[Frankstown Township, Blair County, Pennsylvania|Frankstown]], [[Pennsylvania]] (juvenile [[mastodon]]), and at [[The Mammoth Site]], [[South Dakota]] ([[Columbian mammoth|Columbian mammoths]]). However, questions remain as to whether these finds determine a predatory or scavenging relationship, or whether they were simply preserved at the same deposit.<ref name=":29" /><ref>{{Cite web |date=2010-02-17 |title=A Baby Mastodon Deathtrap (?) |url=https://www.nationalgeographic.com/science/article/a-baby-mastodon-deathtrap |access-date=2022-06-09 |website=Science |language=en}}</ref> On the other hand, a [[woolly mammoth]] specimen from [[Saltville, Virginia|Saltville]], [[Virginia]] was likely scavenged on by ''Arctodus simus'', as evidenced by a [[Canine tooth|canine]] gouge through the [[calcaneus]].<ref name=":33">{{Cite journal |last1=Schubert |first1=Blaine W. |last2=Wallace |first2=Steven C. |date=August 2009 |title=Late Pleistocene giant short-faced bears, mammoths, and large carcass scavenging in the Saltville Valley of Virginia, USA |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.2009.00090.x |journal=Boreas |language=en |volume=38 |issue=3 |pages=482–492 |doi=10.1111/j.1502-3885.2009.00090.x|s2cid=129612660 }}</ref> Several Columbian mammoth bones from a cave near [[Huntington North Dam|Huntington Dam]], [[Utah]] also record ursid gnaw marks attributed to ''Arctodus'', with an ''Arctodus'' specimen preserved in association with the remains.<ref name=":38" /> A [[mastodon]] [[humerus]] from the [[Snowmastodon site]] in [[Colorado]] bears tooth marks also suggested to be from ''Arctodus''.{{Citation needed|date=June 2022}} Importantly, the canines of ''[[American lion|Panthera atrox]]'' overlap in size with ''Arctodus simus'', complicating the identification of tooth marks.<ref name=":33" /> [[File:SpectacledBear1 CincinnatiZoo.jpg|thumb|222x222px|''Arctodus''<nowiki/>' closest extant relative, the [[spectacled bear]], could provide a behavioural analogue for their extinct [[Tremarctinae|tremarctine]] relatives.]] Endemic to the [[Andes|South American highlands]], the last surviving [[Tremarctinae|short-faced bear]] is the [[spectacled bear]]. Although mostly herbivorous, the modern [[spectacled bear]] is on occasion an active predator. The [[spectacled bear]] has several hunting techniques- principally, the bear surprises or overpowers its prey, mounts its back, and consumes the immobilized animal while still alive, pinning the prey with its weight, large paws and long claws. Alternatively, the bear pursues the prey into rough terrain, hillsides, or precipices, provoking its fall and/or death. After death, the prey is dragged to a safe place (e.g. a forested area) and consumed, leaving only skeletal remains.<ref>{{Cite journal|last1=Soibelzon|first1=Leopoldo H.|last2=Grinspan|first2=Gustavo A.|last3=Bocherens|first3=Hervé|last4=Acosta|first4=Walter G.|last5=Jones|first5=Washington|last6=Blanco|first6=Ernesto R.|last7=Prevosti|first7=Francisco|date=November 2014|title=South American giant short-faced bear (Arctotherium angustidens) diet: evidence from pathology, morphology, stable isotopes, and biomechanics |journal=Journal of Paleontology |volume=88|issue=6|pages=1240–1250|doi=10.1666/13-143|s2cid=54869873 |url=http://naturalis.fcnym.unlp.edu.ar/repositorio/_documentos/sipcyt/bfa004877.pdf}}</ref> These behaviors may be applicable to the giant short-faced bears ''[[Arctotherium]]'' and ''Arctodus''. ==== Competition with brown bears ==== [[Brown bear]]s, along with [[American lion|lions]], [[bison]] and [[red fox]]es, first emigrated to [[North America]] via [[Beringia]] during the [[Illinoian (stage)|Illinoian Glaciation]] (~170,000 BP).<ref name=":19" /> ''Arctodus simus'' may have been out-competed by [[brown bear]]s as the latter expanded southwards from eastern [[Beringia]], and gradually established itself in [[North America]]. Both species have been reported together in Alaska before ∼34,000 BP, and in later Pleistocene deposits in [[Maricopa, California|California]], and in [[Nevada]]. However, data from [[Vancouver Island]] suggests that both species occupied the island in quick succession of each other in the [[Late Pleistocene|latest Pleistocene]] (''Arctodus simus'' at ∼13,500 BP), and the [[brown bear]] just before (14,500 BP) and after ''Arctodus simus'' (13,000 BP).<ref name=":15" /> With only a couple of hundred years separating them, a 2018 study concluded that both species were present in the [[Vancouver Island]] area during the latest Pleistocene, but did not overlap territorially. This could be interpreted as [[Niche differentiation|niche partitioning]], to reduce competition for territory and cave use in these sympatric species. Although post-glacial shifts in available resources may also have eventuated in the extirpation of [[brown bear]]s from [[Vancouver Island|Vancouver island]], unlike ''Arctodus simus'', brown bears persisted in adjacent areas.<ref name=":15" /> Meat consumption is confirmed by elevated isotope (''[[δ13C|δ]]''^[[δ13C|13]][[δ13C|C]] and [[δ15N|''δ''¹⁵N]]) values in numerous [[Beringia]]n [[late Pleistocene]] ''Arctodus simus'' specimens where these bears may have competed for food, but usually occupied a higher [[trophic level]] compared with invading brown bears. For example, inland [[Beringia|Beringian]] [[Brown bear|brown bears]] from the late Pleistocene (exception being to specimens from the [[Yukon]]) consumed [[Embryophyte|terrestrial vegetation]] and [[salmon]] at similar proportions to modern coastal populations, whereas modern inland populations of northern brown bears showed no signatures associated with significant [[salmon]] consumption. In both inland populations of Late Pleistocene Beringian brown bears, reduced signatures of terrestrial meat consumption were noted. On the other hand, data from Beringian specimens of ''Arctodus'' suggest that while omnivorous, terrestrial sources of meat were important for northern ''Arctodus''. This contrast is represented in the data- isotopic data from Beringian ''Arctodus'' clusters tightly, and groups differently to Beringian brown bears, although there is overlap.<ref name=":40" /> The forcing of a smaller bear into a more herbivorous diet has been compared to the modern relationship between brown bears and [[American black bear|American black bears]].<ref name=":27" /><ref name=":31" /> That ''Arctodus simus'' (along with the expansion of [[Mire|peatlands]]) may have excluded brown bears from Eastern Beringia from ∼34,000 to ∼23,000 BP further suggests that ''Arctodus'' may typically have been dominant over brown bears.<ref name=":42" /><ref name=":43">{{Cite journal |last=Barnes |first=I. |last2=Matheus |first2=P. |last3=Shapiro |first3=B. |last4=Jensen |first4=D. |last5=Cooper |first5=A. |date=2002-03-22 |title=Dynamics of Pleistocene Population Extinctions in Beringian Brown Bears |url=https://www.science.org/doi/10.1126/science.1067814 |journal=Science |language=en |volume=295 |issue=5563 |pages=2267–2270 |doi=10.1126/science.1067814 |issn=0036-8075}}</ref> When ''Arctodus'' went extinct in Beringia ~23,000 BP, [[brown bear]]s recolonised [[Beringia]], but had more carnivorous diets than their [[Beringia]]n kin pre ~34,000 BP. This bolsters the idea that these bears competed for similar resources and niches.<ref name=":19" /><ref name=":15" /> Similarly, while more herbivorous in Beringia while competing with ''Arctodus'', brown bears seem to have been more carnivorous when co-existing with cave bears in [[Eurasia]] (''[[Cave bear|Ursus spelaeus]]'').<ref name=":31" /> On a continent-wide scale, the 2018 study explained that although brown and ''Arctodus simus'' were [[Sympatry|sympatric]] at times as brown bears spread through North America, ''Arctodus simus'' may typically have dominated [[Competition (biology)|competitive]] interactions, particularly when their populations were robust, and displaced brown bears from specific localities. At the end of the Pleistocene one reason [[brown bear]]s persisted where ''Arctodus simus'' went extinct was because ''Arctodus'' may have been less flexible in adapting to new and rapidly changing environments that impacted the availability or quality of food and possibly habitat.<ref name=":15" /> ==== Hibernation ==== [[File:Fall in the Ozarks.jpg|thumb|231x231px|Although [[North America|pan-continental]], ''Arctodus'' specimens have been particularly plentiful from [[Karst|caves]] in the [[Montane ecosystems|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], such as the [[Ozarks]].]] According to a 2003 study, in [[Karst|karst regions]], fossils of ''Arctodus simus'' have been recovered almost exclusively from cave sites. In the contiguous United States, 26 of 69 ''Arctodus simus'' sites (~38%) are in caves. That greater than one-third of all sites are caves suggests a close association between this species and cave environments. Furthermore, over 70% of the smaller specimens (once assigned as the ''A. s. simus'' subspecies) are from cave deposits. Not one of the specimens assigned to the larger morph (''A. s. yukonensis'') is from a cave passage. Taking into account the fact that female [[Bear|ursids]] are smaller and more prone to den in caves, it seems logical to conclude that the majority of ''Arctodus simus'' from such deposits were females and may have been denning when they perished.<ref name=":2" /> In the [[Americas]], the [[spectacled bear]], [[brown bear]], and [[American black bear|black bear]] use caves for denning when available, and polar bears dig their own “caves” in snow.<ref name=":2" /> Female [[American black bear|black bears]] and [[brown bear]]s in cooler climates enter dens earlier and stay for longer than males. Female [[American black bear|black bears]] and [[brown bear]]s in warmer portions of their range, along with pregnant female [[polar bear]]s, usually den, and often go into [[dormancy]], [[torpor]] and/or maternal denning in winter, while males stay active all year.<ref name=":12" /> Female specimens of ''Arctodus simus'' have been inferred to have been exhibiting maternal denning, however the expression of metabolic denning ([[hibernation]]/torpor) is unclear in ''Arctodus.''<ref name=":3" /> Moreover, to date, there are no records of adults with associated offspring from caves.<ref name=":12" /> However, ''[[Arctotherium|Arctotherium angustidens]]'', a fellow [[Tremarctinae|giant short-faced bear]], has recovered from a cave in [[Argentina]] with offspring.<ref>{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Pomi |first2=Lucas H. |last3=Tonni |first3=Eduardo P. |last4=Rodriguez |first4=Sergio |last5=Dondas |first5=Alejandro |date=2009-09-01 |title=First report of a South American short-faced bears' den (Arctotherium angustidens): palaeobiological and palaeoecological implications |url=https://doi.org/10.1080/03115510902844418 |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=33 |issue=3 |pages=211–222 |doi=10.1080/03115510902844418 |s2cid=55636895 |issn=0311-5518}}</ref> Numerous "bear" beds often preserve ''Arctodus simus'' and both Pleistocene and modern [[American black bear]]s in association (''U.a. amplidens'' and ''U. a. americanus'')- such deposits have been found in [[Missouri]] and [[Oklahoma]]. These mixed deposits are assumed to have accumulated over time as individual bears (including ''Arctodus'') died during winter sleep.<ref>{{Cite journal |last1=Czaplewski |first1=Nicholas |last2=Rogers |first2=Kyler |last3=Russell |first3=Clayton |date=2018-06-01 |title=Late pleistocene vertebrates from three-forks cave, Adair county, Oklahoma Ozark highland |journal=Journal of Cave and Karst Studies |url=https://www.researchgate.net/publication/324068143 |volume=80 |issue=2 |pages=1–16 |doi=10.4311/2017PA0118|doi-access=free }}</ref> Furthermore, [[environmental DNA]] suggests that ''Arctodus'' and black bears shared a cave in [[Chiquihuite cave]] in [[Zacatecas]].<ref name="Pedersen 2728–2736.e8" /> At the [[Schell Creek Range|Labor-of-Love cave]] in [[Nevada]], both American black bears and [[Brown bear|brown bears]] have been found in association with ''Arctodus simus''. A study in 1985 noted that [[sympatry]] between ''Arctodus'' and brown bears preserved in caves is rare, with only [[Converse County, Wyoming|Little Box Elder Cave]] in [[Wyoming]] and Fairbanks II site in [[Alaska]] hosting similar remains.<ref name=":13" /><ref name=":36" /> ==== Pathologies ==== Beyond dietary dental pathologies present in the genus, the most nearly complete skeleton of ''Arctodus'' preserves extensive pathologies on the skeleton. One hypothesis suggests the [[Fulton County, Indiana|Fulton County]] ''Arctodus'' specimen suffered from a [[syphilis]]-like ([[Treponemal diseases|trepanemal]]) disease, or [[yaws]], based on [[Lesion|lesions]] on the [[Vertebra|vertebrae]], [[ribs]] and both [[Ulna|ulnae]].<ref name=":39" /><ref>{{Cite book |last1=Rothschild |first1=Bruce M. |url=https://books.google.com/books?id=AGfmCQAAQBAJ&dq=%22arctodus%22+treponemal+infection+rothschild&pg=PA105 |title=Skeletal Impact of Disease: Bulletin 33 |last2=Martin |first2=Larry D. |date=2006 |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref><ref>{{Cite journal |last=Rothschild |first=Bruce M. |date=13 October 1988 |title=Scientific Correspondence |url=https://www.nature.com/articles/335595a0.pdf?origin=ppub |journal=Nature |volume=335 |issue=Existence of syphilis in a Pleistocene bear |pages=595|doi=10.1038/335595a0 |pmid=3050529 |s2cid=4280184 }}</ref> However, alternate hypotheses include [[tuberculosis]], [[osteomyelitis]], [[arthritis]] or a [[fungal infection]], either singularly or in combination with other causes. The same individual records a pathological growth distorting the [[Deltoid muscle|deltoid]] and [[Pectoral muscles|pectoral]] ridges on the right [[humerus]].<ref name=":1" /> Furthermore, [[Dental abscess|abscesses]] are noted between the m1 and m2 of both [[dentaries]], and on [[Abscess|both ulna]]. Hypotheses include syphilis, [[osteoarthritis]], a fungal infection in addition to long term syphilis, or an infected wound.<ref name=":39" /> == Discussions regarding diet == === "Super predator" hypothesis === [[File:DSC09100 - Extinct Bear (37221999825).jpg|thumb|Skeletal reconstruction of ''Arctodus simus''.]] One past proposal, suggested by paleontologist [[Björn Kurtén]], envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed the [[megafauna]] of the Pleistocene with its great physical strength.<ref name=":16">{{Cite journal |last=Mattson |first=David J. |date=1998 |title=Diet and Morphology of Extant and Recently Extinct Northern Bears |journal=Ursus |volume=10 |pages=479–496 |jstor=3873160 }}</ref> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":21" /><ref name=":22" /> significantly more [[Gracility|gracile]] so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":20" /> Because its long legs may have enabled ''Arctodus'' to run at speeds of {{Convert|50|-|70|km/h|mph|sigfig=1|abbr=on}}, an alternative hypothesis is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, and even prey such as [[mammoth]]s, an idea that at one time earned it the name "running bear".<ref name="Figueiridio_et_al_2010" /><ref name=":21" /><ref>{{Cite web |date=2018-03-02 |title=The Giant Short-Faced Bear |url=https://bear.org/the-giant-short-faced-bear/ |access-date=2022-03-01 |website=North American Bear Center}}</ref> However, during pursuit of speedy game animals, the bear's sheer physical mass and [[Plantigrade|plantigrade gait]] would be a handicap; modern [[brown bear]]s can run at the same speed but quickly tire and cannot keep up a chase for long. ''Arctodus'' skeletons do not articulate in a way that would have allowed for quick turns – an ability required of any predator that survives by chasing down agile prey.<ref name="Simus" /><ref name=":21" /> Additionally, the morphology of the lumbar vertebrae of ''Arctodus'', being akin to the brown bear limited acceleration. The tight & rectangular spines of ''Arctodus'', and no leverage for the [[Intertransversarii|intertransversarial]] muscles to flex the vertebral column (indicating a limited capacity for [[flexion]] and extension in the [[sagittal plane]]) likely led to a lower maximal running speed. Combined with proportionally taller legs, a short trunk, and proportionally small and laterally-orientated [[Orbit (anatomy)|orbits]], ambush hunting was an unlikely lifestyle for ''Arctodus''.<ref name=":1" /> However, analysis of the forelimb of ''Arctodus'' suggests the bear was in the early stages of [[cursorial]] evolution- ''A. simus'' was somewhat more prone to [[Cursorial|cursorial tendencies]], being capable of more efficient locomotion, ''A. simus'' was interpreted as capable of high-speed (relative to extant bears), straight-line locomotion, and was likely more adept at pursuing large prey than the extant [[Polar bear|polar]] and [[brown bear]]s.<ref name=":22">{{Cite book|last=Randally|first=Lynch, Eric |title=Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, Arctodus simus, Revealed by Traditional and 3D Landmark Morphometrics|date=2012-08-06|publisher=East Tennessee State University|oclc=818344518}}</ref> However, that the limbs are elongated in the proximal rather than distal limb segments, the plantigrade gait, and a stride which had little to no unsupported intervals, put doubt to this theory.<ref name=":13" /> Moreover, the pronation of the forearm and the flexion of the wrist and digits, and more lightly muscled forelimbs, all of which are crucial to grasping a large prey animal with the forepaws, were probably less powerful in ''Arctodus'' than in either the [[brown bear]] or in ''[[Panthera]].''<ref name=":1" /> Ultimately, the lack of specialised predatory adaptions (such as the absence of [[Canine tooth|laterally compressed canines]], and [[carnassial]]s built for crushing and grinding rather than shearing meat) puts doubt to any species-wide [[Hypercarnivore|hyper-carnivorous]] interpretations of ''Arctodus.''<ref name="Figueiridio_et_al_2010" /><ref name="Meloro 133–146" /><ref name=":1" /> Although the only extant [[Hypercarnivore|hyper-carnivorous]] [[Bear|ursid]], the [[polar bear]], also lacks conventional [[Carnassial|carnassial shears]] (they are backwards), the species' primary subsistence on [[blubber]] rather than coarser flesh may negate the need to evolve dentition specialized in processing meat (the [[Polar bear|polar bear's]] recent evolution notwithstanding).<ref name=":1" /><ref name=":30" /><ref name=":13" /> === Specialist kleptoparasite vs Omnivore === [[File:Mammut americanum humerus with tooth marks.jpg|thumb|left|[[American mastodon]] arm bone with ''A.&nbsp;simus'' tooth marks at the [[Denver Museum of Nature & Science]] in [[Denver]], [[Colorado]]]][[File:Shortfacedbear-1070375.jpg|thumb|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of [[Molar (tooth)|molar]] damage associated with processing bone, [[Tooth decay|dental cavities]], and the lack of specialisation in the [[Canine tooth|canines]], discourages a [[Hypercarnivore|hyper-carnivorous]] interpretation of ''Arctodus''.|226x226px]]''Arctodus'' moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialised than modern bears. The large body size, taller front legs, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of useable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus" /><ref name=":21" /> Notably proposed by paleontologist Paul Matheus, ''A.&nbsp;simus'', according to these arguments, was ill-equipped to be an active predator, leading to the conclusion that ''Arctodus'' was a [[Kleptoparasitism|kleptoparasite]],<ref name="Simus" /> having evolved as a specialized scavenger adapted to cover an extremely large home range in order to seek out broadly and unevenly distributed [[Carrion|mega-mammal carcasses]].<ref name=":1" /> Under this model, there would have been additional selective pressure for increased body size, so that ''Arctodus'' could procure and defend carcasses from other large carnivores, some of which were gregarious, or chase them from their kills and steal their food.<ref name=":21">{{Cite book|last=E.|first=Matheus, Paul |title=Locomotor adaptations and ecomorphology of short-faced bears (Arctodus simus) in eastern Beringia|date=2003|publisher=Yukon Palaeontologist, Gov't. of Yukon|oclc=243520303}}</ref> Furthermore, the short [[Rostrum (anatomy)|rostrum]], resulting in increased out-forces of the jaw-closing muscles ([[Temporalis muscle|temporalis]] and [[Masseter muscle|masseter]]), may have been an adaptation for cracking bones with their broad [[carnassial]]s. Such use of the P4 and m1 teeth is supported by the heavy wear on these teeth in old individuals of ''Arctodus simus'' and ''[[Agriotherium]]'' (another giant bear).<ref name=":1" /> Moreover, at least in [[Beringia]], the conservative growth strategies, long lives and low natural mortality rates of [[Wild horse|horses]] and [[Woolly mammoth|mammoths]] should have provided somewhat evenly distributed carcasses throughout the year (unlike [[Ruminant|ruminants]] such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":27" /> Additionally, that the tooth fracture frequencies of [[Dire wolf|dire wolves]], [[Machairodontinae|saber-toothed cats]], and [[American lion|American lions]] from [[La Brea Tar Pits|Rancho La Brea]] were recorded at three times the frequency of comparative extant large carnivores, competition was more intense during the Late Pleistocene, and therefore species both scavenged more actively, and utilized carcasses more fully.<ref name=":33" /> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into North America and [[Siberia]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play (although many other fauna did not cross the [[Beringia|Beringian gap]], such as [[Megalonyx|ground sloths]] and the [[Woolly rhinoceros|woolly rhino]]).<ref name=":29" /><ref>{{Cite web |title=Beringia: Lost World of the Ice Age (U.S. National Park Service) |url=https://www.nps.gov/articles/aps-v12-i2-c8.htm |access-date=2022-06-09 |website=www.nps.gov |language=en}}</ref><ref>{{Cite journal |last=Blinnikov |first=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=October 2010 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://linkinghub.elsevier.com/retrieve/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21-22 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002}}</ref><ref>{{Cite journal |last=Blinnikov |first=Mikhail S. |last2=Gaglioti |first2=Benjamin V. |last3=Walker |first3=Donald A. |last4=Wooller |first4=Matthew J. |last5=Zazula |first5=Grant D. |date=2011-10-01 |title=Pleistocene graminoid-dominated ecosystems in the Arctic |url=https://www.sciencedirect.com/science/article/pii/S027737911100206X |journal=Quaternary Science Reviews |language=en |volume=30 |issue=21 |pages=2906–2929 |doi=10.1016/j.quascirev.2011.07.002 |issn=0277-3791}}</ref> This idea was challenged by a comprehensive review by Figueirido and colleagues in 2010,<ref name="Figueiridio_et_al_2010" /> a 2013 study of the micro-wear of the teeth of various extant and extinct bears (examining ''Arctodus'' specimens from [[La Brea Tar Pits|La Brea]]), and a 2015 study focusing on [[carnivora]]ns recovered from [[Rancho La Brea]].<ref name="Donohue">{{cite journal |author1=Donohue, Shelly L. |author2=DeSantis, Larisa R. G. |author3=Schubert, Blaine W. |author4=Ungar, Peter S. |year=2013 |title=Was the giant short-faced bear a hyper-scavenger? A new approach to the dietary study of ursids using dental microwear textures |journal=PLOS ONE |volume=8 |issue=10 |page=e77531 |doi=10.1371/journal.pone.0077531|pmc=3813673 |pmid=24204860|bibcode=2013PLoSO...877531D |doi-access=free }}</ref><ref name=":17">{{Cite journal |last1=DeSantis |first1=Larisa |last2=Schubert |first2=Blaine |last3=Schmitt-Linville |first3=Elizabeth |last4=Ungar |first4=Peter |last5=Donohue |first5=Shelly |last6=Haupt |first6=Ryan |date=2015-01-01 |title=Dental Microwear Textures of Carnivorans from the La Brea Tar Pits, California, and Potential Extinction Implications |url=https://www.researchgate.net/publication/282253545 |journal=La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas |pages=37–52}}</ref> Habitual scavengers like [[hyena]]s show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from [[La Brea Tar Pits|Rancho La Brea]], researchers concluded that ''Arctodus simus'' was not a specialized scavenger. Of living bears, this population of ''A. simus'' showed the most similar tooth wear patterns to its closest living relative, the [[spectacled bear]], which can have a highly varied diet- from obligate omnivory to, on the most part, being almost purely herbivorous in diet.<ref name=":13" /> However, this depends on the region, and seasonal availability.<ref name="Donohue" /> Moreover, severe tooth crown fractures and alveolar infections were found in the South American giant short faced bear ([[Arctotherium|''Arctotherium'' ''angustidens'']]). These were interpreted as evidence of feeding on tough materials (e.g. bones), which could tentatively indicate for these bears the regular scavenging of ungulate carcasses obtained through [[kleptoparasitism]]. However, such dental pathologies were not observed in the specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_2010" /> Additionally, the short, broad [[Rostrum (anatomy)|rostrum]] of ''Arctodus'' is a characteristic also shared with the [[sun bear]] and the [[spectacled bear]], which are both [[Omnivore|omnivorous]].<ref name="Figueiridio_et_al_2010" /> Moreover, isotope analyses of Beringian ''Arctodus'' specimens suggest that ''Arctodus'' had a low consumption rate of horses and mammoths in Beringia, despite those species making up ~50% of the available biomass in Beringia.<ref name=":31" /> Furthermore, the relative lack of ''Arctodus'' remains at [[predator trap]]s such as the [[La Brea Tar Pits|La Brea tar pits]], suggests that ''Arctodus'' did not compete for carcasses.<ref name=":14" /> Although [[La Brea Tar Pits|La Brea]] has produced more ''Arctodus simus'' specimens than any other site (presumably due to the quality of preservation with tar), they are only 1% of all carnivorans in the pits,<ref name=":17" /> which is a similar rate to [[Brown bear|brown bears]] and [[American black bear|black bears]], both omnivorous [[Bear|ursids]] which lean towards herbivory.<ref>{{Cite journal |last1=McHorse |first1=Brianna K. |last2=Orcutt |first2=John D. |last3=Davis |first3=Edward B. |date=2012-04-15 |title=The carnivoran fauna of Rancho La Brea: Average or aberrant? |url=https://www.sciencedirect.com/science/article/pii/S0031018212000958 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=329-330 |pages=118–123 |doi=10.1016/j.palaeo.2012.02.022 |issn=0031-0182}}</ref> As only two specimens were located from the [[Natural Trap Cave]] in [[Wyoming]] by 1993, a similar rate (~0.9%) of relative abundance was calculated for ''Arctodus'' compared to other [[megafauna]] at the site.<ref>{{Cite journal |last1=Wang |first1=Xiaoming |last2=Martin |first2=Larry |date=1993-01-01 |title=Late Pleistocene, paleoecology and large mammal taphonomy, Natural Trap Cave, Wyoming |url=https://www.researchgate.net/publication/267156684 |journal=National Geographic Research & Exploration |volume=9 |pages=422–435}}</ref> Dental pathologies which have been found, such as [[incisor]] wear & [[Calculus (dental)|supragingival dental calculus]] in a young individual,<ref name=":2" /> and [[Tooth decay|cavities]] associated with [[carbohydrate]] consumption in individuals from [[La Brea Tar Pits|La Brea]], further suggest an omnivorous diet for ''Arctodus simus''.<ref name=":14" /> ==== Comparisons with modern fauna ==== [[File:Brown bear (Ursus arctos arctos) running.jpg|thumb|Significant parallels can be found with the once contemporary [[brown bear]] (''Ursus arctos'') and [[hyena]]s.]]The most commonly accepted ecological parallel of ''Arctodus simus'' in scientific literature is the [[brown bear]].<ref name="Figueiridio_et_al_2010" /><ref name=":15" /> Both being the most dominant [[Carnivora|carnivorans]] of North America in the Late Pleistocene and Holocene respectively, both species exhibit a high degree of dietary variability. Noting that [[Dietary biology of the brown bear|brown bears are largely herbivorous]], meat can be an important dietary element to certain populations. ''Arctodus'' follows a similar eco-morphology- while much evidence suggests herbivory, isotope data from some populations of ''Arctodus'' (such as those in [[Beringia]]) suggests the regular consumption of meat.<ref name=":30" /><ref name=":31" /> Additionally, the potential of [[kleptoparasitism]] is often noted in ''Arctodus'', with brown bears being opportunistic, curious, and regularly steal kills from smaller predators.<ref name=":27" /><ref name=":31" /> Another extant model for the eco-morphology of ''Arctodus'' may be the [[striped hyena]] and the [[brown hyena]]. ''Arctodus simus'' resembled these two living [[Hyena|hyaenids]], along with the predatory [[spotted hyena]], in skull shape and relative lengths of the trunk, back and limbs. The [[Striped hyena|striped]] and [[brown hyena]]s supplement their diet of large animal carrion and small animal prey with plant material in the form of [[fruit]], which can make up to half of the diet of some individuals of the [[brown hyena]] at certain times of the year.<ref name=":1" /> Another comparison can be made with the omnivorous [[maned wolf]] of [[South America]]. The [[maned wolf]] inhabits [[Grassland|open grassland]], has extremely long and slender limbs relative to body size (as has sometimes been interpreted in ''Arctodus simus''), is not especially fast, nor does it take swift prey, and runs with a loping gait. The long limbs may be an adaptation for increased vision over tall ground cover in an open habitat. However, it is equally possible that the longer limbs of ''Arctodus simus'' were used in tearing and pulling down vegetation, including [[shrub]]s and small trees, in order to feed on [[Leaf|leaves]], [[fruit]]s or [[Bark (botany)|bark]].<ref name=":13" /> === Herbivory === [[File:Juniperus communis fruits - Keila.jpg|thumb|231x231px|Bear faeces found at [[The Mammoth Site]] in South Dakota containing [[Juniper berry|''Juniperus'' seeds]] likely belonged to ''Arctodus''. [[Conifer cone|Seed cones]] and [[Berry (botany)|berries]] are still an important food source for northern bears today.]] That ''Arctodus'' did not significantly differ in dentition or build from modern bears has lead most authors to support the hypothesis that the ''A. simus'' and the [[cave bear]] were omnivores, like most modern bears, and the former would have eaten plants depending on availability.<ref name="ScienceDaily">ScienceDaily, 13&nbsp;April 2009.{{cite web |url=https://www.sciencedaily.com/releases/2009/04/090408170815.htm |title=Prehistoric bears ate everything and anything, just like modern cousins |website=ScienceDaily |access-date=2009-04-13 }}</ref> A 2006 study found dental and cranial adaptations for herbivory present in ''Arctodus simus'', suggest that the diet of the ''Arctodus'' included a large amount of plant material. Their cranial adaptations for increased bite force (including the short [[Rostrum (anatomy)|rostrum]]), broad [[Snout|muzzles]] (which would have precluded selective browsing), and the absence of digging adaptations in their forelimbs and claws (which would have limited [[Dietary biology of the brown bear#Plants and fungi|rooting]]) suggest that the plant material in their diet was coarse foliage, which was unselectively grazed.<ref name=":1" /> Emslie and Czaplewski suggested that the body size of ''Arctodus simus'' exceeded the expected upper limitations for a [[Quaternary]] terrestrial carnivore (based on the more restrictive energy base for a carnivorous diet). This size discrepancy, along with a [[dentition]] akin to ''[[Spectacled bear|Tremarctos ornatus]]'', indicated a primarily herbivorous diet, but with the potential for opportunistic carnivory.<ref name=":13" /> This was challenged, specifically on the basis of ''Arctodus''<nowiki/>' skull and body proportions being a impediment to foraging (especially in open areas), and the abundance of contemporary large prey.<ref name=":16" /> However, again, due to the [[gracility]] and lack of agility of ''Arctodus'', ''Arctodus'' could probably neither prey upon adult [[Megafauna|mega-herbivores]],<ref name=":21" /><ref name=":22" /> nor actively chase down nimbler prey.<ref name="Simus" /><ref name=":21" /> Morphologically, ''Arctodus simus'' exhibits characteristics common to herbivorous bears. This includes cheek teeth with large surface areas, a deep mandible, and large mandibular muscle attachments (which are rare in carnivorous mammals). Because herbivorous carnivorans lack an efficient digestive tract for breaking down plant matter via microbial action, they must break down plant matter via extensive chewing or grinding, and thus possess features to create a high [[mechanical advantage]] of the jaw.<ref name=":13" /><ref name="Donohue" /> While features of ''Arctodus simus'' morphology suggest herbivory, their close phylogenetic relationship to the omni-herbivorous [[spectacled bear]] presents the possibility that these traits may be an ancestral condition of the group. Regardless, gross tooth wear suggests consumption of at least some plant matter in the diet of ''Arctodus simus'' at [[La Brea Tar Pits|La Brea]]''.'' Despite presumed variety in the diet of ''Arctodus simus'', the diet of individuals from [[La Brea Tar Pits|La Brea]] were likely less generalized than modern [[American black bear|black bear]], based on the consistency of ''Arctodus''<nowiki/>' tooth wear throughout the late Pleistocene at [[La Brea Tar Pits|La Brea]].<ref name="Donohue" /> Fossils of bear [[Coprolite|coprolites]] found in association with ''Arctodus'' remains at [[The Mammoth Site]] in [[South Dakota]] are believed to contain [[Juniper|''Juniperus'']] seeds.<ref name=":29" /> === Beringia === [[File:Wolf with Caribou Hindquarter.jpg|thumb|''Arctodus'' is suggested to have had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|Beringian wolves]], akin to modern [[Wolf|wolves]] and [[Brown bear|brown bears]].|230x230px]]Currently, all specimens of ''Arctodus'' in [[Beringia]] have been dated to a 21,000 year window (44,000 BP~23,000 BP) from Eastern Beringia ([[Alaska]] and the [[Yukon]]).<ref name=":19" /><ref name=":15" /> Analysis of bones from [[Alaska]] showed high concentrations of [[Isotopes of nitrogen#Nitrogen-15|nitrogen-15]], a stable nitrogen isotope accumulated by carnivores. Additionally, although few specimens exist, there is currently no evidence of the same carbohydrate-related [[Tooth decay|dental pathologies]] evident in southern populations of ''Arctodus simus''.<ref name=":14" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more [[Carnivore|carnivorous]] in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C3 vegetation]], particularly [[Reindeer|caribou]]).<ref name=":31" /><ref name=":41">{{Cite journal |last=Fox-Dobbs |first=Kena |last2=Leonard |first2=Jennifer A. |last3=Koch |first3=Paul L. |date=2008-04-24 |title=Pleistocene megafauna from eastern Beringia: Paleoecological and paleoenvironmental interpretations of stable carbon and nitrogen isotope and radiocarbon records |url=https://www.sciencedirect.com/science/article/pii/S0031018208000266 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=261 |issue=1 |pages=30–46 |doi=10.1016/j.palaeo.2007.12.011 |issn=0031-0182}}</ref> Assuming a [[Hypercarnivore|hyper-carnivorous]] diet, the average (700 kg) [[Beringia|Beringian]] ''Arctodus'' individual needed to consume ~5853 kg of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|caballine horses]], or 2 [[Woolly mammoth|woolly mammoths]] (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain 100 kg of flesh/edible [[carrion]] every 6.25 days (consuming {{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus">{{cite web |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |title=The Biggest Bear ... Ever |author=Nancy Sisinyak |publisher=Alaska Fish and Wildlife News |access-date=2008-01-12}}</ref><ref name=":27" /><ref>{{cite journal |author1=Bocherens, H. |author2=Emslie, S. D. |author3=Billiou, D. |author4=Mariotti A. |year=1995 |title=Stable isotopes (13C, 15N) and paleodiet of the giant short-faced bear (''Arctodus simus'') |journal=C R Acad Sci |volume=320 |pages=779–784 |url=https://www.academia.edu/751564}}</ref> A 2015 study suggests that caribou could not account for the high levels of [[Δ13C|carbon-13]] and [[Nitrogen 15|nitrogen-15]] in some ''Arctodus'' individuals in Beringia. The study suggests that the consumption of [[muskox|tundra muskox]], which sometimes express high proportions of these isotopes, and possibly other predators in its Beringian range, may explain the data. The idea that ''Arctodus'' had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|wolves]] and ''[[Homotherium]]'' was also explored.<ref name=":31" /> Additionally, ''Arctodus'' possibly restricted brown bears and ''Homotherium'' access to [[Reindeer|caribou]] pre-[[Last Glacial Maximum|LGM]].<ref name=":41" /> Studies point out that ''A. simus'' would have had a varied diet across its range,<ref name="Donohue" /> and that the features of the skull and teeth match modern omnivorous bears. Additionally, the isotope data purportedly establishing the carnivory of Beringian ''Arctodus'' overlapped with modern, [[Dietary biology of the brown bear|omni-herbivorous]] brown bears from [[Europe]], eastern [[Wyoming]], and central [[Montana]], demonstrating that isotope data cannot distinguish between [[hypercarnivore]]s and [[Omnivore|omnivores]] which eat a significant amount of animal matter.<ref name=":1" /> However, this has been challenged on the basis that herbivory should be more obvious in the data gathered from ''Arctodus''.<ref name=":33" /> Upon the flooding of the [[Bering Strait]] and [[Paludification|expansion]] of [[Mire|peatlands]] in Eastern Beringia during [[MIS 3|MIS-3]], [[Panthera spelaea|lions]], [[brown bear]]s and ''[[Homotherium]]'' went regionally extinct ~35,000 BP, whereas ''Arctodus'' persisted. Simultaneously, [[muskox]], [[bison]], non-caballine horses (''[[Haringtonhippus]]'') and other megafaunal herbivores in Beringia experienced population bottlenecks in MIS-3, whilst [[Woolly mammoth|mammoth]] populations steadily declined. This restriction of prey and habitat could explain the extinctions. However, that genetically distinct ''[[Panthera spelaea]]'' and brown bears reappear in [[MIS 2|MIS-2]] circa the extinction of ''Arctodus'' in a re-emerged Beringia ~23,000 BP (possibly due to sharp climatic cooling associated with [[Heinrich event|Heinrich Event-2]]) opening up the possibility that some level of competition was at play.<ref name=":19" /><ref name=":31" /><ref name=":42">{{Cite journal |last=Murchie |first=Tyler J. |last2=Monteath |first2=Alistair J. |last3=Mahony |first3=Matthew E. |last4=Long |first4=George S. |last5=Cocker |first5=Scott |last6=Sadoway |first6=Tara |last7=Karpinski |first7=Emil |last8=Zazula |first8=Grant |last9=MacPhee |first9=Ross D. E. |last10=Froese |first10=Duane |last11=Poinar |first11=Hendrik N. |date=2021-12-08 |title=Collapse of the mammoth-steppe in central Yukon as revealed by ancient environmental DNA |url=https://www.nature.com/articles/s41467-021-27439-6 |journal=Nature Communications |language=en |volume=12 |issue=1 |pages=7120 |doi=10.1038/s41467-021-27439-6 |issn=2041-1723}}</ref><ref name=":43" /> Not only did ''Arctodus'' likely compete at a higher [[trophic level]] than the majority of brown bears in Beringia, ''Arctodus''<nowiki/>' [[Nitrogen 15|nitrogen-15]] levels are higher in the Yukon, suggesting that ''Arctodus'' possibly occupied an even higher trophic level there relative to other ''Arctodus'' in Beringia. However, isotope differences more likely reflect subtle differences in the isotopic composition of primary producers in the region.<ref name=":40" /><ref>{{Cite journal |last=Lanoë |first=François B. |last2=Reuther |first2=Joshua D. |last3=Holmes |first3=Charles E. |last4=Hodgins |first4=Gregory W. L. |date=2017-11-01 |title=Human paleoecological integration in subarctic eastern Beringia |url=https://www.sciencedirect.com/science/article/pii/S0277379117300999 |journal=Quaternary Science Reviews |language=en |volume=175 |pages=85–96 |doi=10.1016/j.quascirev.2017.10.003 |issn=0277-3791}}</ref> It would be reasonable to assume that meat and bone marrow were likely to be the primary food resources for some northern populations of ''A. simus'', in which the survival during the cold season could have depended on the regular scavenging of [[ungulate]] carcasses, as is the case with [[Kodiak bear|Alaskan brown bears]].<ref name="Figueiridio_et_al_2010" /> Ultimately, an opportunistic foraging strategy including up to 50% vegetation, and the meat of reindeer, muskox, [[carrion]], and possibly some predators, is consistent with the isotopic data and the conclusions of the ecomorphological studies.<ref name=":31" /> Regardless, the local extinction of ''Arctodus'' in [[Beringia]] ~23,000 BP,<ref name=":19" /><ref name=":15" /> much earlier than in other parts of its range, raises questions about how suited ''Arctodus'' was to a hypothetically [[Hypercarnivore|carnivorous]] niche, and why, whilst recolonized by [[Panthera spelaea|cave lions]] and [[brown bear]]s from Western Beringia, ''Arctodus'' didn't repopulate [[Beringia]] once the ice-free corridor to the south re-opened later in the [[Pleistocene]].<ref name=":19" /><ref>{{Cite journal |last1=Pedersen |first1=Mikkel W. |last2=Ruter |first2=Anthony |last3=Schweger |first3=Charles |last4=Friebe |first4=Harvey |last5=Staff |first5=Richard A. |last6=Kjeldsen |first6=Kristian K. |last7=Mendoza |first7=Marie L. Z. |last8=Beaudoin |first8=Alwynne B. |last9=Zutter |first9=Cynthia |last10=Larsen |first10=Nicolaj K. |last11=Potter |first11=Ben A. |date=2016 |title=Postglacial viability and colonization in North America's ice-free corridor |journal=Nature |volume=537 |issue=7618 |pages=45–49 |doi=10.1038/nature19085 |pmid=27509852 |bibcode=2016Natur.537...45P |s2cid=4450936 |url=http://eprints.gla.ac.uk/138297/1/138297.pdf }}</ref> == Human interaction == [[File:Clovis Point.jpg|thumb|The [[Clovis culture|Clovis people]] are the first known culture to have interacted with ''Arctodus''.]]One documented interaction with [[Clovis culture|Clovis people]] is present at the [[Lubbock Lake Landmark]], [[Texas]]. A likely already deceased ''Arctodus simus'' was processed for subsistence (butchery marks indicated skinning, de-fleshing and disarticulation) and technology (raw material resource for tool production), much in the same way as a [[Columbian mammoth|mammoth carcass]] (~13,000 BP / 11,100 [[Carbon-14|¹⁴C]] BP ).<ref name=":11" /> Additionally, other remains of the ''Arctodus simus'' have been found in association with [[Paleo-Indians|Paleo-Indian]] artifacts in [[Sheriden Cave]], [[Wyandot County, Ohio|Ohio]].<ref>{{Cite journal |last=Tankersley |first=Kenneth B. |date=26 May 1997 |title=Sheriden: A Clovis cave site in eastern North America |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/(SICI)1520-6548(199709)12:6%3C713::AID-GEA9%3E3.0.CO;2-1 |journal=Geoarchaeology: An International Journal |volume=12 |issue=6 |pages=713–724}}</ref><ref>{{Cite journal |last=Redmond |first=Brian G. |last2=Tankersley |first2=Kenneth B. |date=10 February 2005 |title=Evidence of Early Paleoindian Bone Modification and Use at the Sheriden Cave Site (33WY252), Wyandot County, Ohio |url=https://www.cambridge.org/core/product/identifier/S0002731600039020/type/journal_article |journal=American Antiquity |language=en |volume=70 |issue=3 |pages=503–526 |doi=10.2307/40035311 |issn=0002-7316}}</ref><ref name="Redmond">{{cite web |author=Brian G. Redmond, PhD., Curator of Archaeology |date=March 2006 |title=Before the Western Reserve: An Archaeological History of Northeast Ohio |url=https://www.cmnh.org/CMNH/media/CMNH_Media/C-R%20Docs/BeforeWR.pdf |access-date=January 28, 2020 |publisher=The Cleveland Museum of Natural History |page=2}}</ref> It was once thought that humans moving into [[North America]] may have found large Pleistocene carnivores such as ''Arctodus simus'' to be a barrier to gaining a foothold.<ref name=":27" /> [[Beringia]]n forms of ''Arctodus'' were the largest and most powerful carnivorous land mammals in North America, with the potential specialisation in obtaining and dominating distant and scarce resources. Humans in this hypothesis, though familiar with [[brown bear]]s, would not have been able to effectively contend with the ''Arctodus simus'' and other large Pleistocene carnivores, a situation that would have suppressed human population expansion. However, with the pre-[[Last Glacial Maximum|LGM]] occupation of [[Beringia]] being a certainty,<ref>{{Cite journal |last1=Graf |first1=Kelly E. |last2=Buvit |first2=Ian |date=2017-12-01 |title=Human Dispersal from Siberia to Beringia: Assessing a Beringian Standstill in Light of the Archaeological Evidence |url=https://www.journals.uchicago.edu/doi/full/10.1086/693388 |journal=Current Anthropology |volume=58 |issue=S17 |pages=S583–S603 |doi=10.1086/693388 |s2cid=149080106 |issn=0011-3204}}</ref><ref>{{Cite journal |last=Bourgeon |first=Lauriane |date=2021-06-01 |title=Revisiting the mammoth bone modifications from Bluefish Caves (YT, Canada) |url=https://www.sciencedirect.com/science/article/pii/S2352409X21001814 |journal=Journal of Archaeological Science: Reports |language=en |volume=37 |pages=102969 |doi=10.1016/j.jasrep.2021.102969 |issn=2352-409X}}</ref><ref>{{Cite journal |last=Holen |first=Steven R. |last2=Harington |first2=C. Richard |last3=Holen |first3=Kathleen A. |date=2017 |title=New Radiocarbon Ages on Percussion-Fractured and Flaked Proboscidean Limb Bones from Yukon, Canada |url=https://www.jstor.org/stable/26379757 |journal=Arctic |volume=70 |issue=2 |pages=141–150 |issn=0004-0843}}</ref> and pre-[[Last Glacial Maximum|LGM]] sites across the Americas starting to gain credibility (including [[Chiquihuite cave|Chiquihuite Cave]], with a human visitation date of ~30,000 BP), the extensive overlap with ''Arctodus'' across [[North America]] puts significant doubt to this theory.<ref name=":15" /> Although people were thinly spread throughout the [[Late Pleistocene]] of the [[Americas]], with diverse and potentially isolated archaeological lithic technologies (e.g. [[Clovis culture|Clovis]], Western Stemmed, and Fishtail) there is no evidence that ''Arctodus'', or other Pleistocene carnivores below the [[Laurentide Ice Sheet]] were in any way an impediment to human expansion, especially as traditional dates (~13,000 BP) suggest an even faster dispersal rate across the continent. It is clear that people were at least occasionally involved in the death and/or butchery of several different large non-carnivorous Pleistocene mammals, particularly [[mammoth]]s and [[mastodon]]s. This may at times have put people in competition with ''Arctodus simus'' for carcasses, and possibly for prey. Defence against these large bears as well as abandonment of carcasses are plausible outcomes. The relationship between people and ''Arctodus simus'' is likely to have been uneasy at best.<ref name=":15" /> == Extinction == [[File:Arctodus simus skeletal.jpg|thumb|Skeletal reconstruction of ''Arctodus simus''.]]''Arctodus simus'' went extinct around 12,000 years ago, which was relatively late when compared to other victims of the [[Quaternary extinction|Quaternary extinction event]].<ref>{{Cite journal |last1=Faith |first1=J. Tyler |last2=Surovell |first2=Todd A. |date=2009-12-08 |title=Synchronous extinction of North America's Pleistocene mammals |journal=Proceedings of the National Academy of Sciences |volume=106 |issue=49 |pages=20641–20645 |doi=10.1073/pnas.0908153106 |pmid=19934040 |pmc=2791611 |issn=0027-8424|doi-access=free }}</ref> ''Arctodus'' was also one of the last (16 out of 35) North American megafauna to go extinct, having reached the Pleistocene-Holocene boundary (13,800 BP - 11,400 BP).<ref name=":44" /> Various factors, including the depletion in number of large herbivores,<ref name=":34" /> the diminishing nutritional quality of plants during climate change, and competition with fellow omnivores ([[Paleo-Indians|humans]] and [[brown bear]]s) for food resources, have been suggested as the cause of ''Arctodus simus''<nowiki/>' extinction.<ref name=":11" /> However, multiple studies put doubt on brown bears being culpable in ''Arctodus simus''<nowiki/>' extinction.<ref name=":9" /><ref name=":15" /><ref name=":16" /> Moreover, there is no strong evidence that humans hunted large extinct Pleistocene carnivores in North America, and no clear indication of direct human involvement in the extinction of ''Arctodus simus''.<ref name=":15" /> Additionally, no evidence from [[La Brea Tar Pits|Rancho La Brea]] suggests that food shortages were to blame for the demise of ''Arctodus simus'', or other large bodied [[Carnivora|carnivorans]].<ref name="Donohue" /> Of these factors, vegetation shifts in the latest Pleistocene may have been particularly unfavorable for ''Arctodus simus,'' due to a reduction of quality foraging for subsistence. For example, on [[Vancouver Island]] (∼13,500 BP), vegetation changed rapidly from open [[woodland]]s with abundant [[Pinus contorta|lodgepole pine]] to increasingly closed forests with shade-tolerant [[Picea|spruce]], [[Tsuga mertensiana|mountain hemlock]], and [[Alnus rubra|red alder]]. These changes, effective by ∼12,450 BP, point toward cool and moist conditions during the [[Younger Dryas|Younger Dryas stadial]]. Closed forests continued to expand in the [[Greenlandian|early Holocene]], with [[Tsuga heterophylla|western hemlock]] becoming dominant. Even though ''Arctodus simus'' was not restricted to open areas and could occur in different environments, the timing of the regional shift from an open pine [[woodland]] habitat to a densely forested vegetation implies that these vegetation changes contributed to the local extirpation of ''Arctodus simus'', along with many other megafauna.<ref name=":15" /> The youngest date for ''Arctodus simus'' is circa 12,700 BP from [[San Antonio|Friesenhahn Cave]], [[Texas]], calibrated from 10,814 ± 55 [[Radiocarbon year|radiocarbon years]] ([[Carbon-14|¹⁴C]] BP). However, this date should be viewed with caution, as analyses suggest the collagen protein was degraded. A vertebra from [[Bonner Springs, Kansas|Bonner Springs]], [[Kansas]], was dated to ca. 12,800 BP (based on 10,921 ± 50 radiocarbon years) from well preserved collagen. However, another radiocarbon date from a different laboratory on the same vertebra widens the possible age of the vertebra to between 9,510–11,021 ¹⁴C BP (at 2''σ''). Nevertheless, a specimen from [[Huntington North Dam|Huntington Dam]], [[Utah]] was also dated to ca. 12,800 BP from two radiocarbon dates (10,870 ± 75 & 10,976 ± 40 ¹⁴C BP) and is therefore considered reliable.<ref name=":12" /><ref name=":44" /> A specimen from the [[McKittrick Tar Pits|McKittrick Tar Seeps]] in [[California]] was dated to 11,040 ± 310 ¹⁴C BP.<ref name=":45">{{Cite journal |last=Fox-Dobbs |first=Kena |last2=Dundas |first2=Robert. G. |last3=Trayler |first3=Robin B. |last4=Holroyd |first4=Patricia A. |date=January 2014 |title=Paleoecological implications of new megafaunal 14 C ages from the McKittrick tar seeps, California |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2013.791694 |journal=Journal of Vertebrate Paleontology |language=en |volume=34 |issue=1 |pages=220–223 |doi=10.1080/02724634.2013.791694 |issn=0272-4634}}</ref> The central and southern [[Rocky Mountains]] may have acted as refugia for ''Arctodus simus'', in addition to other contemporary high-elevation fauna such as ''[[Columbian mammoth|Mammuthus colombi]]'', ''[[Mastodon|Mammut americanum]]'', ''[[Equus conversidens|Equus sp]]'', and ''[[Bison latifrons|Bison sp]].'' ≤11,400 BP (10,000 ¹⁴C BP).<ref name=":44" /><ref name=":38">{{Cite journal |last1=Gillette |first1=David D. |last2=Madsen |first2=David B. |date=1992-03-06 |title=The short-faced bear Arctodus simus from the late Quaternary in the Wasatch Mountains of central Utah |journal=Journal of Vertebrate Paleontology |volume=12 |issue=1 |pages=107–112 |doi=10.1080/02724634.1992.10011436 }}</ref> == Directly sampled specimens == === Radiocarbon dated specimens === Below is a table collating [[Radiocarbon dating|radiocarbon dates]] directly sampled from ''Arctodus simus'' specimens (not including dates from associated remains nor stratigraphy).<ref name=":24" /><ref name="Pedersen 2728–2736.e8" /><ref name=":12" /><ref name=":15" /><ref name=":44" /><ref name=":47" /><ref name=":45" /><ref>{{Cite journal |last=O'Keefe |first=F. Robin |last2=Fet |first2=Elizabeth V. |last3=Harris |first3=John M. |date=2009-12-04 |title=Compilation, calibration, and synthesis of faunal and floral radiocarbon dates, Rancho La Brea, California |url=https://www.biodiversitylibrary.org/part/226783 |journal=Contributions in science |volume=518 |pages=1––16 |doi=10.5962/p.226783 |issn=0459-8113}}</ref><ref>{{Cite journal |last=Mann |first=Daniel H. |last2=Groves |first2=Pamela |last3=Kunz |first3=Michael L. |last4=Reanier |first4=Richard E. |last5=Gaglioti |first5=Benjamin V. |date=2013-06-15 |title=Ice-age megafauna in Arctic Alaska: extinction, invasion, survival |url=https://www.sciencedirect.com/science/article/pii/S0277379113001200 |journal=Quaternary Science Reviews |language=en |volume=70 |pages=91–108 |doi=10.1016/j.quascirev.2013.03.015 |issn=0277-3791}}</ref><ref>{{Cite journal |last=Mann |first=Daniel H. |last2=Groves |first2=Pamela |last3=Reanier |first3=Richard E. |last4=Gaglioti |first4=Benjamin V. |last5=Kunz |first5=Michael L. |last6=Shapiro |first6=Beth |date=2015-11-17 |title=Life and extinction of megafauna in the ice-age Arctic |url=https://pnas.org/doi/full/10.1073/pnas.1516573112 |journal=Proceedings of the National Academy of Sciences |language=en |volume=112 |issue=46 |pages=14301–14306 |doi=10.1073/pnas.1516573112 |issn=0027-8424 |pmc=4655518 |pmid=26578776}}</ref> {| class="wikitable" |+ !Location !Element & ID !¹⁴C Date (1''σ'') !¹⁴C Range (2''σ)'' !Calibrated dates |- |[[San Antonio|Friesenhahn Cave]], [[Texas]] |[[Wisdom tooth|M3]] [[Molar (tooth)|molar]] [[Dentin|dentine]] (TMM 933-2205) |10,814 ± 55 BP |10,704–10,924 BP |~12,700 BP |- |[[Bonner Springs, Kansas|Bonner Springs]] ([[Kansas River]]), [[Kansas]] |[[Lumbar vertebrae|Lumbar vertebra]] (KUVP 81230) ~ [[Femur]] (KUVP 131586) |9630 ± 60 BP 10,921 ± 50 BP¹ 11,688 ± 50 BP |N/A 10,821–11,021 BP¹ 11,588–11,788 BP |~12,800 BP¹ |- |[[Huntington North Dam|Huntington Dam]], [[Utah]] |[[Maxilla]] (UMNH VP 9510) |10,870 ± 75 BP 10,976 ± 40 BP |~ 10,896–11,056 BP |~12,800 BP |- |[[McKittrick Tar Pits|McKittrick Tar Seeps]], [[California]] |[[Ulna]] (UCMP 153245) |11,040 ± 310 BP |N/A |N/A |- |[[Fulton County, Indiana|Fulton County]], [[Indiana]] |[[Rib]] |11,500 ± 520 BP* |N/A |N/A |- |[[Sheriden Cave]], [[Ohio]] |[[Carpal bones|Scapholunar]] (CMNH 2001) ~ ~ [[Talus bone|Astragalus]] ~ |11,480 ± 60 BP 11,566 ± 40 BP¹ 11,570 ± 50 BP 11,570 ± 70 BP 11,610 ± 90 BP |11,486–11,646 BP¹ |N/A |- |[[Nimpkish Lake|Pellucidar Cave]], [[Vancouver Island]] |[[Palatine bone|Palatine]] (PC2–1c) M2 molar dentine (PC2–1a) [[Humerus]] (PC2-3) |11,615 ± 30 BP 11,720 ± 50 BP 11,775 ± 30 BP |N/A |13,379–13,557 BP 13,477–13,725 BP 13,575–13,964 BP |- |[[Salt Lake Valley]] ([[Lake Bonneville|Bonneville]]), [[Utah]] |Femur (UVP 015/1) |12,650 ± 70 BP* |N/A |N/A |- |[[San Miguel Island]] (Daisy Cave), California |[[Metacarpal bones|Metacarpal I]] (PSU-5973) |14,130 ± 70 BP |N/A |17,009 ± 135 BP |- |[[Saltville (archaeological site)|Saltville Valley]], [[Virginia]] |M2 molar dentine |14,853 ± 55 BP |N/A |N/A |- |[[Camden County, Missouri|Perkins Cave]], [[Missouri]] |Dentine |16,910 ± 50 BP |N/A |N/A |- |[[Frontier County, Nebraska|La Sena]], [[Nebraska]] |I3 [[incisor]] dentine |19,487 ± 95 BP |19,297–19,677 BP |N/A |- |[[Dawson City|Gold Run Creek]], [[Yukon]] |N/A |26,040 ± 270 BP |N/A |N/A |- |[[Last Chance Creek|Hester Creek]], Yukon |Radius (YG 76.4) |26,520 ± 110 BP | |~30,800 BP |- |[[Alaska North Slope|Ikpikpuk River]], [[Alaska]] |Humerus |27,160 ± 280 BP |N/A |N/A |- |[[Dawson City|Canyon Creek]], Yukon |Femur (fragment, YG 546.562) |27,850 ± 220 BP | |~31,800 BP |- |[[La Brea Tar Pits]], California |Humerus (LACMRLP 19258) [[Metatarsal bones|Metatarsal]] (LACMRLP 54077) [[Cervical vertebrae|Cervical VI]] (LACMRLP 42063) |27,330 ± 140 BP 28,130 ± 330 BP 28,350 ± 470 BP |N/A |N/A |- |[[Dawson City|Lower Hunker Creek]], Yukon |Humerus |29,600 ± 1200 BP |N/A |N/A |- |[[Adair County, Oklahoma|Gittin Down Mountain Cave]], [[Oklahoma]] |M2 molar dentine (UAM75-839-1) |34,063 ± 460 BP |33,143–34,983 BP |N/A |- |[[Alleghany County, Virginia|Island Ford Cave]], Virginia |M1 molar dentine (USNM 521336) |34,080 ± 480 BP |33,120–35,040 BP |N/A |- |[[Alaska North Slope|North Slope]], Alaska |[[Metapodial]] (UAMES T99-033) |42,600 ± 2,200 BP 46,500 ± 3,600 BP |N/A |~43,570 BP 41,365 - 64,621 BP |- |[[Dawson City|Ophir Creek]], Yukon |[[Petrous bone|Petruous bone]] (YG 24.1) |~46,500 BP¹ <s>(20,210 ± 110 BP)</s> |N/A |~49,800 BP¹ |} === DNA samples === This table collates the current DNA samples extracted from ''Arctodus'' specimens.<ref name="Pedersen 2728–2736.e8" /> {| class="wikitable" |+ !Location !DNA extract ID !¹⁴C Date (1''σ'') & source !Calibrated dates |- |[[Chiquihuite cave|Chiquihuite Cave]] |UE1605 |11,419 ± 34 BP / 11,942 ± 33 / 12,901 ± 75 BP (sediments) |15,000 - 13,000 BP |- |Hester Creek, Yukon |PH092 |26,520 ± 110 BP (radius (YG 76.4)) |~30,800 BP |- |Canyon Creek |N/A |27,850 ± 220 BP (femur (YG 546.562)) |~31,800 BP |- |Ophir Creek, Yukon |PH095 |~46,500 BP (petruous bone (YG 24.1)) |~49,800 BP |} ==See also== *''[[Arctotherium]]'' *[[Pleistocene megafauna]] *[[Quaternary extinction|Quaternary Extinction Event]] ==References== {{commons category|Arctodus}} {{Reflist}} {{Ursidae extinct nav}} {{Taxonbar|from=Q2626037}} [[Category:Pleistocene bears]] [[Category:Pleistocene carnivorans]] [[Category:Pleistocene extinctions]] [[Category:Prehistoric mammals of North America]] [[Category:Pleistocene mammals of North America]] [[Category:Extinct animals of the United States]] [[Category:Extinct animals of Mexico]] [[Category:Fossil taxa described in 1854]] [[Category:Apex predators]]'