View source for Arctodus

{{Short description|Extinct genus of bears}}
{{Automatic taxobox
| fossil_range = {{geological range|2.5|0.012|[[Pleistocene]]}}
| image = Arctodus simus Page.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)}}
| range_map = Short Faced Bear Range.png
| range_map_caption = ''Arctodus simus'' range
| synonyms = {{collapsible list|bullets=true|title={{small|synonyms of ''A. pristinus''}}
 |''Arctodus haplodon'' {{small|[[Oliver Perry Hay|Hay]] 1902}}
 |''[[Arctotherium]] pristinum'' {{small|[[Edward Drinker Cope|Cope]] 1895}}
 |''[[Ursus (mammal)|Ursus]] haplodon'' {{small|[[Edward Drinker Cope|Cope]] 1896}}
 |''[[Tremarctos]] haplodon'' {{small|[[Édouard Louis Trouessart|Trouessart]] 1897}}
}}
{{collapsible list|bullets=true|title={{small|synonyms of ''A. simus''}}
 |''Arctodus nebrascensis'' {{small|Berger 1930}}
 |''[[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}}
}}
}}'''''Arctodus''''' is an extinct genus of [[short-faced bear]] that inhabited North America during the [[Pleistocene]] (~2.5 [[Year#mya|Mya]] until 12,800 years ago). There are two recognized species: the '''lesser short-faced bear''' (''Arctodus pristinus'') and the '''giant short-faced bear''' (''Arctodus simus''). Of these species, ''A. simus'' was larger, is known from more complete remains, and is considered one of the most [[Charismatic megafauna|charismatic]] of North America's megafauna. ''A. pristinus'' was largely restricted to the Early Pleistocene of the eastern United States, whereas ''A. simus'' had a broader range, with most finds being from the Late Pleistocene of the United States, Mexico and Canada. ''A. simus'' evolved from ''A. pristinus'', but both species likely overlapped in the Middle Pleistocene. Both species are relatively rare in the fossil record.

Today considered to be an enormous omnivore, ''Arctodus simus'' is believed to be one of the largest known terrestrial [[carnivora]]ns that has ever existed. However, ''Arctodus'', like other bears, was highly sexually dimorphic- adult ''A. simus'' ranged between {{convert|300|and|950|kg}}, with females clustering at ≤{{convert|500|kg}}, and males around {{convert|800|kg}}. The largest males stood at {{convert|1.67|m}} at the shoulder, and up to {{convert|3.4|m}} tall on their rear legs. Studies suggest that ''Arctodus simus'' browsed on [[C3 carbon fixation|C<sub>3</sub> vegetation]] and consumed browsing herbivores such as [[deer]], [[Camelidae|camelids]], and [[Tapirus|tapir]]. ''A. simus'' preferred temperate open woodlands but was an adaptable species, taking advantage of many habitats and feeding opportunities.

''Arctodus'' belongs to the [[Tremarctinae]] subfamily of bears, which are endemic to the [[Americas]]. Of these short-faced bears, ''Arctodus'' was the most widespread in North America. However, both species went extinct in the Pleistocene. ''A. pristinus'' went extinct around 300,000 years ago, with ''A. simus'' disappearing ~12,800 years ago in the [[Late Pleistocene extinctions]]. The cause behind these extinctions is unclear, but in the case of ''A. pristinus'', this was likely due to climate change and competition with other ursids, such as the [[American black bear|black bear]] and ''[[Tremarctos floridanus]]''. ''A. simus'' likely went extinct due to ecological collapse disrupting the vegetation and prey it relied on.

==Taxonomy==
[[File:Arctodus pristinus mandible ANSP 98.jpg|right|thumb|Partial mandible of ''A. pristinus'' uncovered from [[Port Kennedy Bone Cave|Port Kennedy Cave]].]]
''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=":262">{{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><ref name=":5" /><ref>{{Cite journal |date=1879-08-01 |title=South Carolina Fossils |journal=Nature |language=en |volume=20 |issue=510 |pages=354–355 |doi=10.1038/020354a0 |bibcode=1879Natur..20..354. |s2cid=4034608 |issn=1476-4687|doi-access=free }}</ref> The scientific name of the genus, ''Arctodus'', derives from Greek, and means "bear tooth". The first fossils of ''Arctodus simus'' were found in the Potter Creek Cave, [[Shasta County, California|Shasta County]], California, by J. A. Richardson in 1878, and were initially described as ''Arctotherium simum'' by [[Edward Drinker Cope]] in 1879.<ref name=":48">{{Cite journal |last=Cope E. D. |year=1879 |title=The cave bear of California |journal=American Naturalist |volume=13 |page=791}}</ref><ref name=":25">{{Cite journal |last=Feranec |first=Robert S. |date=November 2009 |title=Implications of Radiocarbon Dates from Potter Creek Cave, Shasta County, California, USA |journal=Radiocarbon |volume=51 |issue=3 |pages=931–936 |bibcode=2009Radcb..51..931F |doi=10.1017/S0033822200034007 |s2cid=131722109 |doi-access=free}}</ref><ref name=":50">{{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> Historically, all specimens were grouped together under ''A. pristinus'', until a revision by [[Björn Kurtén]] in 1967.<ref name=":8" />

In the 19th and early 20th centuries, specimens of ''Arctodus'' were occasionally referred to ''[[Arctotherium]]'', and vice versa.<ref name=":50" /><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>{{Cite journal |last=Kurtén |first=Björn |date=June 1, 1963 |title=Fossil Bears from Texas |url=https://repositories.lib.utexas.edu/bitstream/handle/2152/29869/tmm-pss-01.pdf?sequence=1 |journal=The Pearce-Sellards Series |volume=1 |via=Texas Memorial Museum, University of Texas}}</ref> However, today neither genera are considered to have overlapped, with the closest point of contact being México, with the giant ''Arctodus simus'' in [[Hueyatlaco|Valsequillo]], [[Puebla]],<ref name=":8" /><ref name=":352">{{Cite journal |last1=Ferrusquía-Villafranca |first1=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 |bibcode=2010QuInt.217...53F |issn=1040-6182}}</ref><ref>{{Cite journal |last1=Arroyo-Cabrales |first1=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 |bibcode=2010QuInt.212..187A |issn=1040-6182}}</ref> and the smaller ''Arctotherium wingei'' in the [[Yucatán Peninsula]].<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|page=20190148|doi=10.1098/rsbl.2019.0148 |pmc=6548739|pmid=31039726}}</ref> Other early researchers believed ''Arctodus'' to be a sister lineage of the [[Agriotheriini|agriotheriin]] ''[[Indarctos]]''.<ref name="evolution">{{cite journal |last1=McLellan |first1=Bruce |last2=Reiner |first2=David C. |year=1994 |title=A Review of bear evolution |url=http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_9/McLellan_Reiner_Vol_9.pdf |url-status=live |journal=Int. Conf. Bear Res. And Manage |volume=9 |issue=1 |pages=85–96 |doi=10.2307/3872687 |jstor=3872687 |archive-url=https://ghostarchive.org/archive/20221009/http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_9/McLellan_Reiner_Vol_9.pdf |archive-date=2022-10-09}}</ref> Sometimes described as the "American cave bear",<ref name=":48" /> ''Arctodus'' should not be mistaken for the similarly large [[Cave bear|Eurasian cave bear]] (''Ursus spelaeus''). As an [[Ursinae|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" />

Fossils of ''Arctodus pristinus'' can be confused with the similarly sized, partially contemporaneous [[Tremarctinae|short-faced bear]], ''Tremarctos floridanus''.<ref name=":262" /> ''Arctodus'' has higher crowned and considerably larger teeth than its relative ''Tremarctos''. ''A. pristinus'' can be distinguished by broader and taller molars on average, but as they are often worn, differentiation can be difficult.<ref name=":5" /> Moreover, diagnosing isolated ''A. simus'' remains (such as femora, scapulae, certain vertebrae, ribs, podials) from brown bears can be challenging, as some large brown bears overlap in dimensions with small ''Arctodus simus''.<ref name=":8" /> Beyond [[Tremarctinae#Anatomy|standard differences between tremarctine and ursine bears]], ''A. simus'' has a more anterior [[protocone]] & extended enamel ridge forming a shearing blade on the [[Maxillary second premolar|maxillary P4]]. The molars are also shorter & broader in ''Arctodus'' than brown bears.<ref name=":156">{{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 |bibcode=2018Geobi..51...61S |doi=10.1016/j.geobios.2017.12.001}}</ref>

===Evolution===
{{Cladogram|{{clade| style=font-size:90%;line-height:90%;
      |1={{dagger}}[[Hemicyoninae]]
      |2={{Clade
         |1={{dagger}}[[Ursavinae]]
         |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]]''
}} }} }} }} }} }} }} }}<nowiki></nowiki>|title=[[Tremarctinae]] within [[Ursidae]]|align=left}}
''Arctodus'' belongs to the subfamily Tremarctinae, which appeared in North America during the earliest parts of the late Miocene epoch in the form of ''[[Plionarctos]]''. The medium-sized ''Arctodus pristinus,'' ''[[Tremarctos floridanus]]'' and ''Arctotherium sp.'' evolved from ''Plionarctos'' in the [[Blancan|Blancan age]] 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=":02">{{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 |issue=1 |pages=79–87 |doi=10.1666/09-113.1 |bibcode=2010JPal...84...79S |s2cid=131532424}}</ref> The genetic divergence date for ''Arctodus'' is ~5.5 million years ago,<ref name="Pedersen 2728–2736.e8" /> around the [[Late Miocene|Miocene]]-[[Zanclean|Pliocene]] boundary (~5 Mya), when tremarctine bears, along with other ursids, experienced an explosive radiation in diversity, as [[C4 carbon fixation|C<sub>4</sub> vegetation]] ([[Poaceae|grasses]]) and open habitats dominated. The world experienced a major temperature drop and increased seasonality, and a faunal turnover which extinguished 70–80% of North American genera.<ref>{{Cite journal |last1=Krause |first1=Johannes |last2=Unger |first2=Tina |last3=Noçon |first3=Aline |last4=Malaspinas |first4=Anna-Sapfo |last5=Kolokotronis |first5=Sergios-Orestis |last6=Stiller |first6=Mathias |last7=Soibelzon |first7=Leopoldo |last8=Spriggs |first8=Helen |last9=Dear |first9=Paul H |last10=Briggs |first10=Adrian W |last11=Bray |first11=Sarah CE |last12=O'Brien |first12=Stephen J |last13=Rabeder |first13=Gernot |last14=Matheus |first14=Paul |last15=Cooper |first15=Alan |date=December 2008 |title=Mitochondrial genomes reveal an explosive radiation of extinct and extant bears near the Miocene-Pliocene boundary |journal=BMC Evolutionary Biology |language=en |volume=8 |issue=1 |page=220 |doi=10.1186/1471-2148-8-220 |issn=1471-2148 |pmc=2518930 |pmid=18662376 |bibcode=2008BMCEE...8..220K |doi-access=free }}</ref><ref name="Donohue2" />

''Arctodus pristinus'' was mostly restricted to the more densely forested thermal enclave in [[Southeastern United States#Climate|eastern North America]].<ref name="Bearalmanac">{{Cite book |last=Brown, Gary |url=https://archive.org/details/greatbearalmanac00gary/page/340 |title=Great Bear Almanac |year=1996 |isbn=978-1-55821-474-3 |page=[https://archive.org/details/greatbearalmanac00gary/page/340 340] |publisher=Lyons & Burford |url-access=registration}}</ref><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. pristinus'' has the greatest concentration of fossils in Florida,<ref name=":5" /> with the earliest finds being from the Late Blancan [[Kissimmee River]] [[Okeechobee County, Florida|6]] (2.7 - 2.2 Mya) and [[Santa Fe River (Florida)|Santa Fe River]] [[Columbia County, Florida|1]] sites.<ref name=":262" /><ref name=":5" /><ref>{{Cite journal |last=Morgan |first=Gary S. |date=2005 |title=The Great American Biotic Interchange in Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/bulletin-Morganlowres.pdf |journal=Bulletin of the Florida Museum of National History |volume=45 |issue=4 |pages=271–311}}</ref> During the early [[Irvingtonian|Irvingtonian age]] (~1.36 million years ago), a western population of ''A. pristinus'' evolved into the enormous ''A. simus,'' being first recorded from the [[Fremont, California#Irvington District|Irvington type locality]] in California.<ref name=":8" /><ref name=":43">{{Cite book |last1=Bell |first1=Christopher |url=https://www.researchgate.net/publication/263425514 |title=Late Cretaceous and Cenozoic Mammals of North America |last2=Lundelius |first2=Ernest L. |last3=Barnosky |first3=Anthony D. |last4=Zarzewski |first4=Richard J. |last5=Graham |first5=Russell |last6=Lindsay |first6=Everett H. |last7=Ruez |first7=Dennis R. |last8=Semken |first8=Holmes A. |last9=Webb |first9=S. David |editor-first1=Michael O. |editor-last1=Woodburne |date=2004-04-21 |publisher=Columbia University Press |isbn=978-0-231-50378-5 |language=en |chapter=Chapter 7: The Blancan, Irvingtonian, and Rancholabrean Mammal Ages |doi=10.7312/wood13040}}</ref> Correspondingly, ''A. simus'' is most plentiful from western North America,<ref name=":132" /><ref name=":9">{{Cite journal |last1=Martin |first1=Larry |last2=Neuner |first2=A. |date=1978-01-01 |title=The End of the Pleistocene in North America |url=https://digitalcommons.unl.edu/tnas/337 |journal=Transactions of the Nebraska Academy of Sciences and Affiliated Societies}}</ref> albeit preferring mixed habitat such as temperate open woodlands.<ref name=":232">{{Cite journal |last1=Trayler |first1=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 |bibcode=2015PPP...437..132T |doi=10.1016/j.palaeo.2015.07.034 |issn=0031-0182}}</ref><ref name=":410">{{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 |bibcode=2018GeoM..155..674P |doi=10.1017/S0016756816000935 |s2cid=132502543}}</ref><ref name=":27" /><ref name=":92" /><ref>{{Citation |last=Akersten |first=William A. |title=Diversity bottlenecks, oddball survivors, and negative keys |date=1996-12-31 |work=Palaeoecology and Palaeoenvironments of Late Cenozoic Mammals |pages=1–15 |url=https://www.degruyter.com/document/doi/10.3138/9781487574154-004/html |access-date=2024-01-23 |publisher=University of Toronto Press |doi=10.3138/9781487574154-004 |isbn=978-1-4875-7415-4}}</ref> Their ranges may have met in the Middle Pleistocene of Kansas,<ref name=":8" /> with ''A. simus'' migrating east in the Late Pleistocene (around the extinction of ''A. pristinus'').<ref name=":02" /><ref>{{Cite journal |last=Phillips |first=George Edward |date=6 August 2006 |title=Paleofaunistics of Nonmammalian Vertebrates from the Late Pleistocene of the Mississippi-Alabama Black Prairie |url=https://repository.lib.ncsu.edu/items/185efe46-230f-4ff1-87be-12da682be6e8 |journal=North Carolina State University (Masters) |via=North Carolina State University Library}}</ref> Although both ''Arctodus'' species co-inhabited North America for at least a million years during the Middle Pleistocene (''A. pristinus'' went extinct ~300,000 [[Before Present|BP]]), there is no direct evidence of [[sympatry|overlap]] or [[Competition (biology)|competition]] in the fossil record as of yet, as both species established largely [[Allopatric speciation|separate ranges]].<ref name=":02" />

Irvingtonian age (1,900,000 BP - 250,000 BP) specimens of ''Arctodus simus'' are particularly sparse. Finds are mostly from California, with additional remains from Texas, Kansas, Nebraska, and Montana.<ref name=":46" /><ref name=":4" /><ref name=":30">{{Cite book |last=Kurtén |first=Björn |url=https://books.google.com/books?id=GkCFtAEACAAJ |title=Pleistocene Bears of North America: Genus Arctodus, short-faced bears |date=1967 |publisher=Societas pro Fauna et Flora Fennica |language=en}}</ref> However, ''A. simus'' became a pan-continental species in the [[Rancholabrean]] (Late Pleistocene), sharing that distinction with the [[American black bear|black bear]].<ref name=":43" /><ref name=":92">{{Cite web |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 |website=ResearchGate}}</ref> Despite ''Arctodus simus''' large temporal and geographic range, fossil remains are comparatively rare (109 finds as of 2010, in otherwise well-sampled localities).<ref name=":02" /><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>

==Description==
=== Size ===
[[File:Arctodus simus Sergiodlarosa.jpg|thumb|left|Restoration of ''Arctodus simus.'']]

==== ''Arctodus pristinus'' ====
Around the size of [[grizzly bear]]s, ''A. pristinus'' specimens closely overlap the size of ''Tremarctos floridanus'', with some males of ''A. pristinus'' overlapping in size with the females of ''A. simus.''<ref name=":262" /> ''A. pristinus'' individuals recovered from the [[Cockroach Bay Aquatic Preserve|Leisey Shell Pit]], Florida, were calculated to an average of ~{{convert|133|kg}}.<ref name=":52">{{Cite journal |last1=Van Valkenburgh |first1=Blaire |last2=Hayward |first2=Matthew W. |last3=Ripple |first3=William J. |last4=Meloro |first4=Carlo |last5=Roth |first5=V. Louise |date=2016-01-26 |title=The impact of large terrestrial carnivores on Pleistocene ecosystems |journal=Proceedings of the National Academy of Sciences |language=en |volume=113 |issue=4 |pages=862–867 |doi=10.1073/pnas.1502554112 |issn=0027-8424 |pmc=4743832 |pmid=26504224|bibcode=2016PNAS..113..862V |doi-access=free }}</ref> However, the dimensions of some individuals from [[Port Kennedy Bone Cave]] and [[Aguascalientes]] suggest that northern and western ''A. pristinus'' may have been larger than Floridan ''A. pristinus'',<ref name=":8" /> being up to {{Convert|400|kg|lb}}.<ref name=":20" />

==== ''Arctodus simus'' ====
Some ''A. simus'' individuals might have been the largest land-dwelling specimens of [[Carnivora]] that ever lived in North America. Standing up on its hind legs, ''A. simus'' stood {{convert|8|-|11|ft|abbr=on|order=flip}},<ref name="Simus2">{{cite web |author=Nancy Sisinyak |title=The Biggest Bear ... Ever |url=http://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232&issue_id=41 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref><ref name=":17">{{Cite web |last=Fisher |first=W. A. |date=2018-02-05 |title=How Big Was This Short-Faced Bear? |url=https://bear.org/how-big-was-this-short-faced-bear/ |access-date=2023-11-02 |website=North American Bear Center |language=en}}</ref> with a maximum vertical arm reach of {{Convert|4.3|m|ft}}.<ref>{{Cite web |title=Giant Short-faced Bear {{!}} Yukon Beringia Interpretive Centre |url=https://www.beringia.com/exhibit/ice-age-animals/giant-short-faced-bear |access-date=2023-12-01 |website=www.beringia.com}}</ref> When walking on all fours, ''A. simus'' stood {{convert|1|-|1.67|m|ft|abbr=on|order=out}} high at the shoulder, with the largest males being tall enough to look an adult human in the eye.<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 name=":17" /><ref name=":1622">{{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> The average weight of ''A. simus'' was ~{{Convert|625|kg|lb}}, with the maximum recorded at {{Convert|957|kg|lb}}.<ref name="Figueiridio_et_al_20102" /><ref name=":52" />

===== <small>Studies</small> =====
In a 2010 study, the mass of six ''A. simus'' specimens was estimated; one-third of them weighed about {{convert|850|kg|lb|abbr=on|0}}, the largest from [[Salt Lake Valley]], Utah coming in at {{convert|957|kg|lb|abbr=on}}, suggesting larger specimens 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 {{Convert|317|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102">{{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 |bibcode=2010JVPal..30..262F |s2cid=85649497}}</ref> 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. |date=2011 |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 |journal=Journal of Paleontology |volume=85 |issue=1 |pages=69–75 |doi=10.1666/10-037.1 |jstor=23019499 |s2cid=129585554 |hdl=11336/104215|hdl-access=free }}</ref> However, a 2006 study argued that the maximum size of ''Arctodus'' was ~{{Convert|555|kg|lb}}, based on the largest known skull.<ref name=":110">{{cite journal |last1=Sorkin |first1=B. |date=January 2006 |title=Ecomorphology of the giant short-faced bears Agriotherium and Arctodus |journal=Historical Biology |volume=18 |issue=1 |pages=1–20 |doi=10.1080/08912960500476366 |bibcode=2006HBio...18....1S |s2cid=85301983}}</ref> Additionally, a 1998 study calculated the average weight of ''Arctodus'' specimens from the [[La Brea Tar Pits]] at ~{{Convert|372|kg|lb}}, smaller than recovered [[brown bear]] remains (~{{Convert|455|kg|lb}}, although these remains 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 |bibcode=1998Ecosy...1..157L |s2cid=29456831 |issn=1432-9840}}</ref><ref name=":362">{{Cite journal |last1=Kurten |first1=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 Per Christiansen calculated a mean weight of ~{{Convert|770|kg|lb}} from six large male ''A. simus'' specimens.<ref name=":7" />

==== Sexual dimorphism ====
[[File:Short Faced Bear FMNH.jpg|thumb|''Arctodus simus'' skeletal at the [[Field Museum of Natural History]], Chicago.]]
There is much variation in adult size among specimens- the lack of finds, [[sexual dimorphism]], individual variation and potentially [[Ecomorphology|ecomorphs]] could be augmenting the average size of both species of ''Arctodus''.<ref name=":5" /><ref name=":8" /><ref name=":6">{{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> Size differences between specimens of ''Arctodus simus'' (such as skull and long bone dimensions) led [[Björn Kurtén|Kurtén]] to suggest a larger northern/central subspecies (''A. s. yukonensis'') and a southern subspecies (''A. s. simus'').<ref name="Figueiridio_et_al_20102" /><ref name=":8">{{Citation |last1=Richards |first1=Ronald L. |title=Distribution and size variation in North American Short-faced bears, Arctodus simus |date=1996-12-31 |url=https://www.degruyter.com/document/doi/10.3138/9781487574154-012/html |work=Palaeoecology and Palaeoenvironments of Late Cenozoic Mammals |pages=191–246 |access-date=2023-11-15 |publisher=University of Toronto Press |doi=10.3138/9781487574154-012 |isbn=978-1-4875-7415-4 |last2=Churcher |first2=C.S. |last3=Turnbull |first3=William D.}}</ref><ref name=":30" /> evolving in the Irvingtonian and Rancholabrean respectively.<ref name=":30" /><ref name=":8" /> However, the discovery of a very large southern ''Arctodus simus'' in Florida and New Mexico (deep within the supposed range of ''A. s. simus''),<ref name=":02" /><ref name=":44">{{Cite book |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=S--oDQAAQBAJ |title=Vertebrate Paleontology in New Mexico: Bulletin 68 |last2=Sullivan |first2=Robert M. |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref> & possibly Rancho La Brea,<ref name=":8" /> and notably small specimens from the [[Yukon]] and [[Vancouver Island]],<ref name="Pedersen 2728–2736.e8" /><ref name=":156" /> put doubt on this designation.<ref name=":36" /> Perceived [[Bergmann's rule|ecomorphologies]] are possibly due to the low number of specimens, and sex-biased sampling.<ref name=":02" />

For example, only one [[baculum]] (penis bone) has been recovered from over 100 giant short-faced bear sites in North America, although it may belong to a black bear (Potter Cave).<ref name=":56" /> None of the specimens assigned to the larger morph (''A. s. yukonensis'') is from a cave passage, being usually isolated remains from open sites. Furthermore, over 70% of the smaller specimens (once assigned as the ''A. s. simus'' subspecies) are from cave deposits where bacula would likely be found if present, suggesting that mostly female individuals of ''A. simus'' were using caves.<ref name=":2">{{Cite journal |last1=Schubert |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><ref name=":8" /> Therefore, in conjunction with ursid sexual dimorphism (e.g. male spectacled bears are 30% - 40% larger than females), the larger, massive ''Arctodus'' individuals are often considered male, particularly older males, with the smaller, more lightly built individuals being females.<ref name=":02" /><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 |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |journal=PaleoBios |volume=15 |issue=2 |pages=27–36 |date=May 24, 1993 |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf}}</ref> Sexual dimorphism may also explain ''A. simus'' teeth (from multiple individuals at the same site) generally clustering into two sizes.<ref name=":8" />

=== Anatomy ===
The two species of ''Arctodus'' are differentiated not only by size, but also by the shorter snout, greater [[prognathism]], more robust teeth and longer limbs of ''A. simus,'' and the relative proportions of each species' molars and premolars. ''Arctodus pristinus'' is distinguished from ''A. simus'' smaller, narrower, and less crowded teeth. However, the morphologies of both species are otherwise very similar. As a result, differentiating ''Arctodus simus'' from ''Arctodus pristinus'' can be difficult, as male individuals of ''Arctodus pristinus'' can overlap in size with female individuals of ''Arctodus simus''.<ref name=":02" /><ref name=":2" /><ref name=":332" /> ''Arctodus simus'' superficially resembled living [[Hyena|hyaenids]] in skull shape and relative lengths of the trunk, back and limbs.<ref name=":110" /> The most nearly complete skeleton of ''A. simus'' found in the United States was unearthed in [[Fulton County, Indiana|Fulton County]], Indiana; the original bones are in the [[Field Museum of Natural History]], Chicago.<ref name=":39" /><ref name=":56" />

==== Skull ====
[[File:Arctodus simus skull Cleveland.jpg|thumb|Male ''A. simus'' skull, photographed at the [[Cleveland Museum of Natural History]] in [[Cleveland]], Ohio.]]Members of the [[Tremarctinae]] subfamily of bears appear to have a disproportionately short snout compared with most modern bears, giving them the name "short-faced". ''Arctodus'' has also been argued to exhibit a wide and shortened [[Rostrum (anatomy)|rostrum]], potentially giving ''Arctodus'' a more [[Felidae|felid]]-like appearance.<ref name=":30" /><ref>{{Cite journal |last1=Goswami |first1=Anjali |last2=Milne |first2=Nick |last3=Wroe |first3=Stephen |date=2011-06-22 |title=Biting through constraints: cranial morphology, disparity and convergence across living and fossil carnivorous mammals |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=278 |issue=1713 |pages=1831–1839 |doi=10.1098/rspb.2010.2031 |issn=0962-8452 |pmc=3097826 |pmid=21106595}}</ref> Matheus suggested that a broad [[snout]] could have housed a highly developed [[Olfactory system|olfactory apparatus]], or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas.<ref name=":402">{{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 |bibcode=1995QuRes..44..447M |s2cid=83542760 |issn=0033-5894}}</ref> However, this apparent shortness is an illusion caused by the deep snouts and short nasal bones of 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 omni-herbivorous [[spectacled bear]].<ref name=":132">{{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 |url=https://www.biodiversitylibrary.org/partpdf/226835 |journal=Contributions in Science |volume=371 |pages=1–12 |doi=10.5962/p.226835 |s2cid=133986793|doi-access=free }}</ref><ref name="Figueiridio_et_al_20102" /><ref name=":302">{{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 |url=http://sedici.unlp.edu.ar/handle/10915/5372 |journal=Lethaia |volume=43 |issue=2 |pages=209–222 |doi=10.1111/j.1502-3931.2009.00184.x}}</ref> Snout deepness could be variable, as specimens from Huntington Reservoir in Utah, and the [[Dallas|Hill-Shuler locality]], Texas, were noted as being distinctly "short-faced" in comparison with other ''Arctodus simus'' individuals.<ref name=":382">{{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|bibcode=1992JVPal..12..107G }}</ref><ref name=":13">{{Cite book |publisher=The University of Texas at Austin, Bureau of Economic Geology |author=Slaughter, B. H. |author2=Crook, W. W. Jr. |author3=Harris, R. K. |author4=Allen, D. C. |author5=Seifert, M. |date=1962-01-01 |title=The Hill-Shuler Local Faunas of the Upper Trinity River, Dallas and Denton Counties, Texas |series=Report Investigation |doi=10.23867/ri0048d |doi-access=free}}</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=":110" /><ref name=":302" /><ref name=":292">{{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 [[optic canal]] and other [[Sphenoid bone|sphenoidal]] openings crowd together more in ''A. simus'' than in ''[[Ursus (mammal)|Ursus]]''.<ref name=":156" /> As with ''Tremarctos ornatus'', specimens with a large [[sagittal crest]] were likely male, whereas females had a reduced or no sagittal crest.<ref name=":5" /> Although there are limited samples, the [[middle ear]] [[Ossicles|bones]] of ''A. simus'' are proportionally larger than modern ursine bears, suggesting the species was particularly attuned to low-frequency sounds.<ref>{{Cite journal |last1=Dickinson |first1=Edwin |last2=Elminowski |first2=Erin E. |last3=Flores |first3=Deanna |last4=Eldridge |first4=Emma I. |last5=Granatosky |first5=Michael C. |last6=Hartstone-Rose |first6=Adam |date=October 2022 |title=A morphological analysis of carnivoran ossicles from Rancho La Brea |journal=Journal of Morphology |language=en |volume=283 |issue=10 |pages=1337–1349 |doi=10.1002/jmor.21506 |issn=0362-2525 |pmc=9826070 |pmid=36041006}}</ref>

Morphologically, ''Arctodus simus'' exhibits masticular characteristics common to herbivorous bears. This includes cheek teeth with large, blunt surface areas, a deep mandible, and large mandibular muscle attachments (which are rare in carnivorous mammals). As herbivorous carnivorans such as ''Arctodus'' lack the [[gut microbiota]] to efficiently break down plant matter, these features created a high [[mechanical advantage]] of the jaw to break down plant matter via extensive chewing or grinding.<ref name=":132" /><ref name="Donohue2">{{cite journal |last1=Donohue |first1=Shelly L. |last2=DeSantis |first2=Larisa R. G. |last3=Schubert |first3=Blaine W. |last4=Ungar |first4=Peter S. |date=30 October 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 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name=":82">{{Cite journal |last=Meloro |first=Carlo |date=2011-03-17 |title=Feeding habits of Plio-Pleistocene large carnivores as revealed by the mandibular geometry |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2011.550357 |journal=Journal of Vertebrate Paleontology |language=en |volume=31 |issue=2 |pages=428–446 |bibcode=2011JVPal..31..428M |doi=10.1080/02724634.2011.550357 |issn=0272-4634 |s2cid=85255472}}</ref> Although the low mandibular [[Mandibular condyle|condyle]] relative to the tooth row (and therefore potential wide gape) of ''Arctodus simus'' has been inferred as an adaptation for carnivory,<ref name=":30" /><ref name=":35">{{Cite journal |last1=Voorhies |first1=M. R. |last2=Corner |first2=R. G. |date=1986 |title=Giant Bear Arctodus as a Potential Breaker and Flaker of Late Pleistocene Megafaunal Remains |journal=Current Research in the Pleistocene |volume=3 |pages=49–51}}</ref><ref name=":156" /> it is also present in the omni-herbivorous spectacled bear.<ref name="Figueiridio_et_al_20102" /> However, both ''Arctodus pristinus'' and ''Tremarctos floridanus'' have condyles raised well above the plane of the teeth.<ref name=":822">{{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> The purpose of the highly vaulted [[Calvaria (skull)|calvarium]] and straight [[Zygomatic arch|cheek bones]] of ''Arctodus simus'' have been similarly disputed.<ref name="Figueiridio_et_al_20102" />

A 2009 analysis of the [[Mandible|mandibular]] morphology of tremarctine bears found notable differences between ''Arctodus pristinus'' and ''Arctodus simus'', with ''A. simus'' specimens possessing a concave jaw, large [[Masseter muscle|masseter]] and [[Temporalis muscle|temporalis]] muscles, deeper horizontal ramus and a reduced slicing dentition length when compared to ''A. pristinus''. Instead, ''Arctodus simus'' was most similar to ''Arctotherium angustidens-'' however, both species of ''Arctodus'' and ''Arctotherium angustidens'' were still comfortably in the "omnivorous" bear cranio-morphotype.<ref name=":302" />

===== <small>Dentition</small> =====
[[File:Arctodus simus molar.png|left|thumb|165x165px|Right lower second molar (M2) of ''Arctodus simus'', from [[La Brea Tar Pits|Rancho La Brea]], California.]]
The [[premolar]]s and [[Molar (tooth)|first molars]] of ''Arctodus pristinus'' are relatively smaller and more widely spaced than those of ''Arctodus simus''.<ref name=":262" /><ref name=":02" /> In ''A. pristinus'', the features of the dentition can be quite variable, particularly the M2 molar.<ref name=":5" /> An analysis of the [[Hunter-Schreger band]]s from the teeth of ''A. pristinus'' and ''A. simus''  demonstrated an evolutionary trend towards partially reinforced [[tooth enamel]]. This has been convergently evolved with giant pandas, [[Agriotheriini|agriotheriin]] bears, and ''[[Hemicyon]]''.<ref name=":21">{{Cite journal |last=Stefen |first=Clara |date=2001 |title=Enamel Structure of Arctoid Carnivora: Amphicyonidae, Ursidae, Procyonidae, and Mustelidae |journal=Journal of Mammalogy |volume=82 |issue=2 |pages=450–462 |doi=10.1644/1545-1542(2001)082<0450:ESOACA>2.0.CO;2 |issn=0022-2372 |jstor=1383726 |s2cid=85871953|doi-access=free }}</ref> The dentition of ''A. simus'' 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 shears) disagrees with this hypothesis.<ref name=":132" /><ref name=":22">{{Cite journal |last1=Figueirido |first1=B. |last2=Palmqvist |first2=P. |last3=Pérez-Claros |first3=J. A. |date=2008-12-22 |title=Ecomorphological correlates of craniodental variation in bears and paleobiological implications for extinct taxa: an approach based on geometric morphometrics |url=https://zslpublications.onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2008.00511.x |journal=Journal of Zoology |language=en |volume=277 |issue=1 |pages=70–80 |doi=10.1111/j.1469-7998.2008.00511.x |issn=0952-8369}}</ref><ref name=":156" />

Dentition can be a poor indicator of size in ''A. simus'', as some medium-size individuals have teeth that surpass the size of those with the largest skeletons.<ref name=":8" /> Additionally, while ''A. simus'' evolved from the smaller ''A. pristinus'', their teeth remained generally the same size.<ref name=":8" /> A specimen of ''A. simus'' from the Seale Pit of the Hill-Shuler locality, Texas, with only two premolars, crowding of the anterior premolar out of line, and a wider and shorter muzzle, was suggested to be an undescribed form of ''Arctodus''.<ref name=":13" />

==== Post-cranial ====
===== <small>Limbs</small> =====
[[File:ArctodusSimusReconstruct.jpg|thumb|''A. simus'' compared with a human.|left]]
Researchers have differing interpretations on the limb morphology of ''Arctodus''. A comprehensive 2010 study concluded that the legs of ''Arctodus'' weren't proportionally longer than modern bears would be expected to have, and that bears in general are long-limbed animals, 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. In fact, ''Arctodus'' probably had an even shorter back than other bears, due the necessary ratio between body length and body mass of the huge bear.<ref name="Figueiridio_et_al_20102" /><ref name=":272" /> However, other researchers argue that the limb bones of ''Arctodus simus'' are proportionally longer than those of other bears, leading to a "gracile" appearance. Although longer, the proportions still overlap with ''Ursus'', and the limb bones are stouter than in the large-bodied felids (''Panthera''). Rather than for running, these elongated limb bones may have evolved for increased locomotor efficiency during prolonged travel.<ref name=":16">{{Cite journal |last1=Jiangzuo |first1=Qigao |last2=Flynn |first2=John J. |last3=Wang |first3=Shiqi |last4=Hou |first4=Sukuan |last5=Deng |first5=Tao |date=2023-03-14 |title=New Fossil Giant Panda Relatives (Ailuropodinae, Ursidae): A Basal Lineage of Gigantic Mio-Pliocene Cursorial Carnivores |journal=American Museum Novitates |issue=3996 |pages=1–71 |doi=10.1206/3996.1 |issn=0003-0082 |s2cid=257508340 |doi-access=free}}</ref><ref name=":212">{{Cite book |last=Matheus |first=Paul E. |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> This stiff-legged, swinging gait could have been similar to a polar bear's.<ref name=":57" /> Some researchers suggest that proportionally longer limbs may be an adaptation for increased vision over tall ground cover in an open habitat, or were used in tearing and pulling down vegetation.<ref name=":132" /><ref name=":1622" />

Researchers also disagree when interpreting the [[humerus]] of ''Arctodus simus''.<ref name=":16" /> Sorkin argued that 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]].'' This is due to a weak medial epicondyle and reduced development of the [[Pronator teres muscle|pronator teres]] muscle.<ref name=":110" /> The forelimb of ''Arctodus'' could have been in the early stages of [[cursorial]] evolution, being capable of more efficient and high-speed straight-line locomotion (relative to extant bears), and was possibly more adept at pursuing large prey than [[Polar bear|polar]] and [[brown bear]]s.<ref name=":222">{{Cite book |last=Lynch |first=Eric Randally |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> On the other hand, some researchers argue that the epicondyles were still well developed, with this wide range of ulna rotation suggests that forearms of ''Arctodus'' were powerful and could subdue large prey.<ref name=":16" /> The shape of the [[Elbow|elbow joint]], along with an well-developed [[Medial epicondyle of the humerus|medial epicondyle]] which forms an angle with the [[condyle]], and shallower [[olecranon fossa]], would have given ''Arctodus'' a higher degree of forelimb dexterity. Originally evolved to facilitate [[Arboreal locomotion|arboreality]], other researchers believe that the terrestrial ''Arctodus'' (along with ''Arctotherium'' and the [[giant panda]]) retained this characteristic to assist in foraging for vegetation.<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 |page=20160062 |doi=10.1098/rsbl.2016.0062 |pmc=4881349 |pmid=27095265}}</ref><ref name=":132" /><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 |url=https://researchonline.ljmu.ac.uk/id/eprint/7536/1/Meloro_et_al-2017-Journal_of_Mammalian_Evolution.pdf |journal=Journal of Mammalian Evolution |volume=26 |issue=1 |pages=133–146 |doi=10.1007/s10914-017-9413-x |s2cid=25839635}}</ref>

===== <small>Paws</small> =====
The [[paw]]s ([[metapodial]]s and [[Phalanx bone|phalanges]]) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to [[Ursinae|ursine bears]]. ''Arctodus''<nowiki/>' paws were therefore more symmetrical than ursine bears, whose feet have axes aligned with the most lateral (fifth) digit. Also, the [[Toe#Hallux|first digit]] 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=":272">{{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=PhD |language=en |first=Paul Edward |last=Matheus}}</ref><ref name=":1622" />{{multiple image
| align             = right
| direction         = vertical
| total_width       = 185
| image1            = Garra Oso de anteojos.JPG
| alt1              = 
| image2            = Spectacled Bear 616md.jpg
| alt2              = 
| footer            = For comparison, the [[Manus (anatomy)|manus]] of the spectacled bear has five digits arrayed in a shallow arc ([[Department of Amazonas, Peru|Chaquil Cave]], Peru).<ref>{{Cite journal |last=Weems |first=Robert E. |date=2018 |title=An Early Pleistocene (Early Irvingtonian) Footprint Fauna from the Bacons Castle Formation, Westmoreland Formation, Virginia |url=https://www.researchgate.net/publication/348579743 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=79 |pages=731–748 |via=ResearchGate}}</ref><ref>{{cite journal | doi=10.2192/08GR017R1.1 | title=A 6,000+ year-old specimen of a spectacled bear from an Andean cave in Peru | date=2009 | last1=Stucchi | first1=Marcelo | last2=Salas-Gismondi | first2=Rodolfo | last3=Baby | first3=Patrice | last4=Guyot | first4=Jean-Loup | last5=Shockey | first5=Bruce J. | journal=Ursus | volume=20 | pages=63–68 | s2cid=86731722 }}</ref>
}}

However this is potentially contradicted by possible ''Arctodus simus'' trackways from near [[Lakeview, Oregon|Lakeview]], Oregon, with strong toe splaying, three centrally aligned & evenly spaced toes at the front, and two almost perpendicular lateral toes (80° from the axis of the foot on either side). The trackways suggest that ''Arctodus'' had an oval-shaped, undivided pad on its sole, 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> An additional ''A. simus'' paw print measuring {{Convert|15|cm|in|abbr=on}} long and {{Convert|19|cm|in|abbr=on}} wide has been recovered from [[White Sands National Park]], New Mexico.<ref>{{Cite journal |last1=Gentry |first1=Andrew |last2=Franco |first2=Christopher Michael |last3=Bustos |first3=David |date=September 2011 |title=Mammalian Ichnofauna from the Upper-Pleistocene deposits of White Sands National Monument, Otero County, New Mexico. |url=https://www.researchgate.net/publication/325261275 |journal=Geoscientists-in-the Parks, National Park Service, Denver, Colorado. |via=ResearchGate}}</ref><ref>{{Cite journal |last1=Nadeau |first1=Andy J. |last2=Allen |first2=Kathy |last3=Benck |first3=Kevin |last4=Davis |first4=Anna M. |last5=Hutchins |first5=Hannah |last6=Gardner |first6=Sarah |last7=Amberg |first7=Shannon |last8=Robertson |first8=Andrew |date=September 2017 |title=White Sands National Monument Natural Resource Condition Assessment |url=http://npshistory.com/publications/whsa/nrr-2017-1508.pdf |journal=Natural Resource Report NPS/WHSA/NRR—2017/1508 |pages=276–277 |via=National Park Service, Fort Collins, Colorado}}</ref> Some claw marks attributed to ''Arctodus simus'' at [[Riverbluff Cave]] (as they were four meters above the floor of the cave) were nearly 20&nbsp;cm in width.<ref name=":1">{{Cite journal |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |title=Cenozoic Vertebrate Tracks and Traces |last2=Spielmann |first2=Justin A. |last3=Lockley |first3=Martin G. |date=2007 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=42 |language=en}}</ref><ref>{{Cite book |last1=Rovey II |first1=Charles W. |chapter-url=https://books.google.com/books?id=HRlx-0ydi4YC&dq=riverbluff+cave&pg=PA31 |title=From Precambrian Rift Volcanoes to the Mississippian Shelf Margin: Geological Field Excursions in the Ozark Mountains |last2=Forir |first2=Matt |last3=Balco |first3=Greg |last4=Gaunt |first4=David |date=2010-01-01 |publisher=Geological Society of America |isbn=978-0-8137-0017-5 |editor-last=Evans |editor-first=Kevin R. |edition=Field Guide 17 |pages=31–32 |language=en |chapter=Geomorphology and Paleontology of Riverbluff Cave, Springfield, Missouri |editor-last2=Aber |editor-first2=James S.}}</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|ursine bears]], the false thumb of the spectacled bear has been suggested to assist in herbivorous food manipulation (such as [[Bromeliaceae|bromeliads]], leaves, berries, tree bark & fruits, cactus fruits & pulp, [[Heart of palm|palm hearts]] & fronds), or [[arboreality]].<ref name=":11">{{Cite journal |last1=Salesa |first1=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|doi-access=free |hdl=10261/22444 |hdl-access=free }}</ref><ref name="Donohue2" /><ref name=":132" />

==== Paleopathology ====
Beyond carbohydrate-associated dental pathologies present in the genus,<ref name=":2" /><ref name=":142">{{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 |bibcode=2017NatSR...717813F |doi=10.1038/s41598-017-18116-0 |pmc=5736623 |pmid=29259277}}</ref><ref name=":156" /> extensive pathologies have been preserved on the most nearly complete skeleton of ''Arctodus''. The leading hypothesis suggests the [[Fulton County, Indiana|Fulton County]] ''Arctodus'' specimen suffered from a [[syphilis]]-like ([[Treponemal diseases|treponemal]]) disease, or [[yaws]], based on the various [[lesion]]s present.<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 |page=595 |doi=10.1038/335595a0 |pmid=3050529 |s2cid=4280184}}</ref> The same individual records a pathological growth distorting the right [[humerus]],<ref name=":110" /> with [[Dental abscess|abscesses]] are noted between the molars 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" /><ref>{{Cite journal |last1=Pinto |first1=A. C. |last2=Etxebarría |first2=F. |date=2001 |title=Description of pathological conditions in the skeleton of an adult male brown bear Ursus arctos from the Cantabrian range of mountains (Reserva Nacional de Caza de Riaño, León) Coruña |url=https://www.udc.es/files/iux/almacen/articulos/cd26_art33.pdf |journal=Cadernos Lab. Xeolóxico de Laxe |volume=2001 |page=471 |issn=0213-4497}}</ref> Several specimens from [[Fairbanks North Star Borough, Alaska|Fairbanks]], Alaska, also exhibit either pathological growths or [[periodontal disease]],<ref name=":8" /> along with a healed toe bone from Big Bear Cave, Missouri.<ref name=":56" />

== Paleobiology ==

=== Locomotion ===
Paul Matheus proposed that ''Arctodus simus'' may have moved in a highly efficient, moderate-speed [[Horse gait#Pace|pacing]] gait, more specialized than modern bears. His research concluded that the large body size, taller front legs, high shoulders, short and sloping back, and long legs of ''Arctodus'' also compounded locomotive efficiency, as these traits swelled the amount of usable [[Strain energy|elastic strain energy]] in the tendons, and increased stride length, making ''Arctodus'' built more for endurance than for great speed.<ref name="Simus2" /><ref name=":212" /> His calculations suggested that ''Arctodus'' likely had a top speed of {{Convert|40-45|km/h|mph}}, and based on hyaenid proportions, would shift from singlefoot locomotion to a pace at {{Convert|8.5|km/h|mph|abbr=on}}, and would begin to gallop at {{Convert|18.5|km/h|mph|abbr=on}}, a fairly high speed. Based on other mammals, the optimal pace speed of ''Arctodus'' would have been {{Convert|13.7|km/h|mph|abbr=on}}. For comparison, hyenas cross country ~{{Convert|10|km/h|mph|abbr=on}}.<ref name=":212" /> This mobility would have facilitated travelling across a large home range, which Mattson suggests may have topped {{Convert|1000|sqmi|km2}}.<ref name=":56" /> Swimming has also been presented as a hypothesis for the colonization of Vancouver Island by ''Arctodus simus''.<ref name=":31" /><ref name=":56" />

=== Maturity ===
Examinations on a mostly full sized young individual of ''Arctodus simus'' from an [[Ozarks|Ozark]] cave suggest that ''Arctodus'', like other ursids, reached [[sexual maturity]] well before [[Bone age|full maturity]]. Comparisons with black bears suggest the ''Arctodus'' specimen 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''. Fused [[Sutures of skull|sutures]], [[Epiphysis|epiphyses]], and [[epiphyseal plate]]s, along with [[tooth eruption]], have been used to determine adulthood in ''Arctodus.''<ref name=":2" /><ref name="Pedersen 2728–2736.e8" />

=== Genetic diversity ===
{{location map+|North America|relief=yes|width=250|float=right|caption=DNA distribution map of ''Arctodus simus''<br />
Legend: [[File:DeepPink pog.svg|8px]] Main mitochondrial haplogroup of ''A. simus'' (haplotypes A, B, C, D, E, F, G)

[[File:Orange pog.svg|8px]] Chiquihuite Cave ''A.simus'' 
[[File:Steel pog.svg|8px]] Unassigned ''A.simus''|places={{location map~ |North America| label = Chiquihuite Cave | position = none | lat= 24.609470 | long= -101.188001 | mark= Orange pog.svg}}

{{location map~ |North America| label = Sheriden Cave (E) | position = none | lat=40.980733 | long=-83.444783| mark= DeepPink pog.svg}}

{{location map~ |North America| label = Natural Trap Cave (N/A) | position = none | lat=44.973333 | long= -108.193056 | mark= Steel pog.svg}}

{{location map~ |North America| label = San Miguel Island (N/A) | position = none | lat=34.033333 |long=-120.383333|mark= Steel pog.svg}}

{{location map~ |North America| label = Clover Bar (Edmonton, F) | position = none | lat=53.596164 | long= -113.354075 | mark= DeepPink pog.svg}}

{{location map~ |North America| label = Cripple Creek (F) | position = none | lat=62.766667 |long=-137.383333 |mark= DeepPink pog.svg}}

{{location map~ |North America| label = Sixtymile River (F) | position = none | lat= 63.554796 | long= -139.825129 | mark= DeepPink pog.svg}}

{{location map~ |North America| label = Dawson (Canyon Creek, Dawson City, Eldorado Creek, Gold Run, Hester Creek, Lower Hunker Creek, Ophir Creek, Quartz Creek, ADF) | position = none | lat=63.97 |long=-139.1 |mark= DeepPink pog.svg}}

{{location map~ |North America| label = Lilian Creek (A) | position = none | lat= 65.516989 | long= -148.573169 | mark= DeepPink pog.svg}}

{{location map~ |North America| label = Fairbanks (Dawson Cut, Ester Creek, Eva Creek Mine, Gold Hill, Goldstream, No.2 G-Strip Area, ABCDFG) | position = none | lat= 64.846267 | long= -147.734202 | mark= DeepPink pog.svg}}}}

An examination of [[mitochondrial DNA]] sequenced from specimens of ''Arctodus simus'' from Alaska, Alberta, Ohio and the Yukon suggest an extremely low level of genetic diversity among the 23 individuals studied (≤ 44,000 [[Radiocarbon dating|<sup>14</sup>C]] BP), with only seven [[haplotype]]s recovered. Genetic diversity was comparable to modern endangered fauna, such as the brown kiwi and African cheetah. Explanations include a [[Population bottleneck|genetic bottleneck]] before 44,000 <sup>14</sup>C BP, or a low level of genetic diversity being a feature of a species which was primarily solitary, with a large home range and relatively small population size.<ref name=":49" /> However, this does not entirely preclude genetic diversity in ''Arctodus simus'', with genetic samples from [[Chiquihuite cave|Chiquihuite Cave]], Zacatecas indicating a deep divergence with previously studied specimens of ''A. simus''.<ref name="Pedersen 2728–2736.e8" /> Additional specimens from the California Channel Islands and Wyoming have been sequenced, but are unassigned.<ref>{{Cite journal |last1=Salis |first1=Alexander T |last2=Gower |first2=Graham |last3=Schubert |first3=Blaine W. |last4=Soibelzon |first4=Leopoldo H. |last5=Heiniger |first5=Holly |last6=Prieto |first6=Alfredo |last7=Prevosti |first7=Francisco J. |last8=Meachen |first8=Julie |last9=Cooper |first9=Alan |last10=Mitchell |first10=Kieren J. |date=2021 |title=Ancient genomes reveal hybridisation between extinct short-faced bears and the extant spectacled bear (Tremarctos ornatus) |url=https://www.biorxiv.org/content/10.1101/2021.02.05.429853v2.full |journal=Current Biology (Preprint) |doi=10.1101/2021.02.05.429853 |s2cid=231885176 |via=CellPress}}</ref><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 |page=15172 |doi=10.1038/s41598-020-71572-z |pmc=7494929 |pmid=32938967}}</ref>

==== Haplotype cladogram ====
Below is a cladogram exploring the relationships between the mitochondrial [[haplogroup]]s of ''Arctodus simus''. Other than the specimen from Chiquihuite Cave, all haplotypes form a single [[clade]].<ref name="Pedersen 2728–2736.e8" /><ref name=":49" />

{{clade sequential|{{clade
           |1=''[[Tremarctos]]'' [[File:Spectacled bear (1829).jpg|75px]]
           |2=''[[Arctotherium]]''
           }}|2=Chiquihuite Cave
        |3={{clade 
           |1=A
           |2=B
           |3=C
           }}
        |4={{clade 
           |1=D
           |2=E
           }}
        |5={{clade 
           |1=F
           |2=G
           }}|position=center}}

== Diet ==
=== Herbivory ===
[[File:Juniperus_communis_fruits_-_Keila.jpg|thumb|231x231px|''Arctodus'' faeces found at South Dakota and the Yukon contain [[Juniper berry|''Juniperus'' seeds]]. [[Conifer cone|Seed cones]] and [[Berry (botany)|berries]] are still important food sources for northern bears today.]]
The fact that ''Arctodus'' did not significantly differ in dentition or build from modern bears has led most authors to support the hypothesis that the ''A. simus'' was omnivorous, like most modern bears, and would have eaten significant amounts of plant matter.<ref name=":22" /><ref name=":23">{{Cite journal |last1=Jones |first1=D. Brent |last2=Desantis |first2=Larisa R. G. |date=2016-06-29 |title=Dietary Ecology of the Extinct Cave Bear: Evidence of Omnivory as Inferred from Dental Microwear Textures |journal=Acta Palaeontologica Polonica |volume=61 |issue=4 |pages=735–741 |doi=10.4202/app.00253.2016 |issn=0567-7920 |s2cid=55803102 |doi-access=free}}</ref> Morphologically, ''Arctodus simus'' exhibits masticular and dental characteristics which confirms that short-faced bears such as the [[spectacled bear]] and ''Arctodus'' were adapted to and actively consumed vegetation.<ref name=":132" /><ref name=":302" /><ref name="Donohue2" /><ref name=":22" /><ref name=":82" /> This is affirmed by a lack of dental damage associated with carnivory amongst specimens of ''Arctodus''.<ref name=":172">{{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> Dental pathologies which have been found, such as [[incisor]] wear & [[Calculus (dental)|supragingival dental calculus]] in a young individual from Missouri,<ref name=":2" /> and [[Tooth decay|cavities]] associated with [[carbohydrate]] consumption in individuals from the La Brea Tar Pits & Pellucidar Cave (Vancouver Island), further suggest an omnivorous diet for ''Arctodus simus''.<ref name=":142" /><ref name=":172" /><ref name=":156" /> Additional morphological adaptations include dexterous forelimbs and a partial [[Sesamoid bone|false thumb]], which would have assisted in foraging for vegetation,<ref name="Meloro 133–146" /><ref name=":11" /> along with the body size of large ''Arctodus simus'' (~1000&nbsp;kg) matching or exceeding the expected upper limitations for a terrestrial carnivore (based on the more restrictive energy base for a carnivorous diet).<ref name=":132" /><ref>{{Cite journal |last1=Carbone |first1=Chris |last2=Teacher |first2=Amber |last3=Rowcliffe |first3=J. Marcus |date=2007-01-16 |title=The Costs of Carnivory |journal=PLOS Biology |language=en |volume=5 |issue=2 |pages=e22 |doi=10.1371/journal.pbio.0050022 |issn=1545-7885 |pmc=1769424 |pmid=17227145 |doi-access=free}}</ref><ref>{{Cite journal |last1=Smith |first1=Felisa A. |last2=Boyer |first2=Alison G. |last3=Brown |first3=James H. |last4=Costa |first4=Daniel P. |last5=Dayan |first5=Tamar |last6=Ernest |first6=S. K. Morgan |last7=Evans |first7=Alistair R. |last8=Fortelius |first8=Mikael |last9=Gittleman |first9=John L. |last10=Hamilton |first10=Marcus J. |last11=Harding |first11=Larisa E. |last12=Lintulaakso |first12=Kari |last13=Lyons |first13=S. Kathleen |last14=McCain |first14=Christy |last15=Okie |first15=Jordan G. |date=2010-11-26 |title=The Evolution of Maximum Body Size of Terrestrial Mammals |url=https://www.science.org/doi/10.1126/science.1194830 |journal=Science |language=en |volume=330 |issue=6008 |pages=1216–1219 |doi=10.1126/science.1194830 |pmid=21109666 |bibcode=2010Sci...330.1216S |s2cid=17272200 |issn=0036-8075}}</ref>

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. A browsing diet foraged from the canopies of trees and shrubs could have been difficult with the large and flattened rostrum and incisor build of ''Arctodus'', with an absence of digging adaptations in ''Arctodus''<nowiki/>' forelimbs and claws limiting [[Dietary biology of the brown bear#Plants and fungi|rooting]].<ref name=":1622" /><ref name=":110" /> Regardless, gross tooth wear suggests consumption of plant matter in the diet of ''Arctodus simus''.<ref name="Donohue2" /><ref name=":132" /> The diet of individuals from La Brea was most similar to the spectacled bear, which consumes tough leafy matter, seeded & pitted fruits and occasional protein. ''Arctodus''<nowiki/>' tooth wear remained consistent throughout the Pleistocene in La Brea. This indicated a less generalized diet than modern omni-herbivorous [[American black bear|black bears]], with none of the dental evidence of hard food consumption (such as carcasses or nuts) found in polar bears, black bears and hyenas.<ref name="Donohue2" /> Comparisons with the dental microwear of ''[[Cave bear|Ursus speleaus]]'' suggest dietary differences between the species, with cave bears consuming tougher vegetation than ''A. simus''.<ref name=":23" /> Although some researchers argue that herbivory should be more obvious from the isotope data gathered from northern ''Arctodus'',<ref name=":332" /> several ''Arctodus'' [[coprolite]]s from [[The Mammoth Site]] in South Dakota and Meander Cave at [[Ni'iinlii'njik (Fishing Branch) Territorial Park|Ni'iinlii'njik Territorial Park]], Yukon contain [[Juniper|''Juniperus'']] seeds (toxic to black & brown bears).<ref name=":292" /><ref name=":15">{{Cite book |last1=Lauriol |first1=Bernard |url=https://emrlibrary.gov.yk.ca/Tourism/ni'iinlii-njik-caves-northern-yukon-2016.pdf |title=The Ni'iinlii Njik Caves, Northern Yukon |last2=Gotthardt |first2=Ruth |publisher=Government of Yukon |year=2016 |isbn=978-1-55362-752-4 |editor-last=Leduc |editor-first=Heather}}</ref>

=== Opportunistic carnivory ===
[[File:SpectacledBear1 CincinnatiZoo.jpg|thumb|''Arctodus''<nowiki/>' closest living relative is the [[spectacled bear]]. Although mostly herbivorous, ''Tremarctos ornatus'' is on occasion an active predator.<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 |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/south-american-giant-shortfaced-bear-arctotherium-angustidens-diet-evidence-from-pathology-morphology-stable-isotopes-and-biomechanics/2616CEF2B348B1453C68EF26CF2858C9 |journal=Journal of Paleontology |language=en |volume=88 |issue=6 |pages=1240–1250 |bibcode=2014JPal...88.1240S |doi=10.1666/13-143 |issn=0022-3360 |s2cid=54869873 |hdl-access=free |hdl=11336/34149}}</ref>|218x218px]]Evidence suggests that ''Arctodus'' also consumed meat, as evidenced by elevated nitrogen-15 isotope levels (corresponding to protein consumption) and bone damage on contemporary fauna. Additionally, elevated carbon-13 levels (corresponding to [[C3 carbon fixation|C<sub>3</sub>]] resources) from many localities (Alaska,<ref name=":312">{{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 |bibcode=2015QSRv..117...42B |doi=10.1016/j.quascirev.2015.03.018 |issn=0277-3791}}</ref> California,<ref name=":232" /><ref name=":47" /> [[San Luis Potosí]],<ref name=":410" /> Texas,<ref name=":33">{{Cite journal |last1=Smith |first1=Felisa A. |last2=Elliott Smith |first2=Emma A. |last3=Villaseñor |first3=Amelia |last4=Tomé |first4=Catalina P. |last5=Lyons |first5=S. Kathleen |last6=Newsome |first6=Seth D. |date=2022-09-27 |title=Late Pleistocene megafauna extinction leads to missing pieces of ecological space in a North American mammal community |journal=Proceedings of the National Academy of Sciences |language=en |volume=119 |issue=39 |pages=e2115015119 |bibcode=2022PNAS..11915015S |doi=10.1073/pnas.2115015119 |doi-access=free |issn=0027-8424 |pmc=9522422 |pmid=36122233}}</ref> Vancouver Island,<ref name=":31" /><ref name=":14">{{Cite journal |last1=Kubiak |first1=Cara |last2=Grimes |first2=Vaughan |last3=Van Biesen |first3=Geert |last4=Keddie |first4=Grant |last5=Buckley |first5=Mike |last6=Macdonald |first6=Reba |last7=Richards |first7=M. P. |date=2022-06-27 |title=Dietary niche separation of three Late Pleistocene bear species from Vancouver Island, on the Pacific Northwest Coast of North America |url=https://onlinelibrary.wiley.com/doi/10.1002/jqs.3451 |journal=Journal of Quaternary Science |language=en |volume=38 |pages=8–20 |doi=10.1002/jqs.3451 |issn=0267-8179 |s2cid=250134103}}</ref> and the Yukon)<ref name=":412" /> largely suggest browsers (and browsed vegetation) were the core of ''A. simus''<nowiki/>' diet.<ref name="Figueiridio_et_al_20102" />

''Arctodus simus''<nowiki/>' status as a predator is questioned by its [[gracility]] and lack of agility, which could have complicated predation upon adult [[Megafauna|mega-herbivores]], and hindered the chasing down of nimbler prey.<ref name=":212" /><ref name=":222" /> Nevertheless, larger (male) ''Arctodus simus'' are suggested to have been more carnivorous than females, as very large brown bears may not be able to sustain themselves on a vegetarian diet.<ref name=":14" /> Furthermore, the much larger frame of ''A. simus'' would have provided an advantage in disputes over carcasses.<ref name=":02" />

Studies establish that ''Arctodus simus'' would have had a varied diet across its range,<ref name="Donohue2" /> and was outcompeted and/or more herbivorous with increased competition from other predators.<ref name=":142" /><ref name=":14" /><ref name=":312" /><ref name=":47" /> The extinction of cursorial, hyper-carnivorous ''[[Borophagus]]'' and [[Huracan (genus)|''Huracan'']] in the more open western North America left a vacant niche, possibly contributing to the evolution of ''A. simus'' (along with changes to the herbivore guild).<ref name=":28" /><ref name=":16" />

==== Bone damage ====
[[File:American_mastodon_with_calf.jpg|thumb|''Arctodus'' may have found young [[proboscidea]]ns to be suitable prey.|left]]The bite marks found on many bones of ground sloths (''[[Nothrotheriops|Northrotheriops texanus]]'') 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=":262" /> Additionally, ''Arctodus pristinus'' was the most common large predator from Port Kennedy Cave, Pennsylvania, where the majority of mastodon remains were juveniles and likely represent accumulated prey.<ref>{{Citation |last=Daeschler |first=Edward B. |title=Selective mortality of mastodons (Mammut americanum) from the Port Kennedy Cave (Pleistocene; lrvingtonian), Montgomery County, Pennsylvania |date=1996-12-31 |work=Palaeoecology and Palaeoenvironments of Late Cenozoic Mammals |pages=83–96 |url=https://www.degruyter.com/document/doi/10.3138/9781487574154-008/html |access-date=2024-01-23 |publisher=University of Toronto Press |doi=10.3138/9781487574154-008 |isbn=978-1-4875-7415-4}}</ref>

''Arctodus simus'' has been found in association with [[proboscidea]]n remains near [[Frankstown Township, Blair County, Pennsylvania|Frankstown]], Pennsylvania (juvenile [[mastodon]]), and at [[The Mammoth Site]], South Dakota ([[Columbian mammoth]]s). However, questions remain as to whether these finds determine a predatory or scavenging relationship, or whether they were simply preserved at the same deposit (possibly at different times).<ref name=":292" /><ref name=":29">{{Cite web |date=2010-02-17 |title=A Baby Mastodon Deathtrap (?) |url=https://www.nationalgeographic.com/science/article/a-baby-mastodon-deathtrap |url-status=dead |archive-url=https://web.archive.org/web/20220609094201/https://www.nationalgeographic.com/science/article/a-baby-mastodon-deathtrap |archive-date=June 9, 2022 |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=":332" /> Several Columbian mammoth bones from a cave near [[Sanpete County, Utah|Huntington Reservoir]], Utah also record ursid gnaw marks attributed to ''Arctodus'', with an ''Arctodus'' specimen preserved in association with the remains.<ref name=":382" />

Importantly, the canines of ''[[American lion|Panthera atrox]]'' overlap in size with ''Arctodus simus'', complicating the identification of tooth marks.<ref name=":332" /> However, this is not to discredit all tooth marks attributed to ''Arctodus'', as damaged bones from near [[Tanana River]], Alaska suggest that ''Arctodus'' transported megafaunal [[Long bone|longbones]] back to a cave-like den and chewed on them,<ref>{{Cite journal |last=Guthrie |first=R. Dale |date=1988 |editor-last=Mead |editor-first=Jim I. |title=Bone Litter from an Alaskan Pleistocene Carnivore Den |url=https://liberalarts.tamu.edu/csfa/wp-content/uploads/sites/14/2023/07/CRP-5-1988.pdf |journal=Current Research in the Pleistocene |volume=5 |pages=84–85}}</ref><ref name=":35" /><ref>{{Cite journal |last=Sattler |first=Robert A. |date=1997 |title=Large Mammals in Lower Rampart Cave 1, Alaska: Interspecific Utilization of an Eastern Beringian Cave |journal=Geoarchaeology |volume=12 |issue=6 |pages=657–688 |doi=10.1002/(SICI)1520-6548(199709)12:6<657::AID-GEA7>3.0.CO;2-Y}}</ref> at a time when lions had a limited overlap with ''Arctodus'' in Beringia.<ref name=":19">{{cite bioRxiv |biorxiv=10.1101/2020.09.03.279117 |first1=Alexander T |last1=Salis |first2=Sarah C E |last2=Bray |title=Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge |date=3 September 2020 |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}}</ref><ref name=":142" /> Furthermore, a perforated [[Platygonus compressus|peccary]] ilium from [[Sheriden Cave]] has also been hypothesized as being scavenged by ''Arctodus simus''.<ref name=":322" /> Bone damage on a [[Cranium|cranial fragment]] (and possibly the humerus) of an ''Arctodus'' individual on [[Vancouver Island]] may have been due to [[cannibalism]].<ref name=":156" /><ref name=":14" />

==== Beringia ====
Analysis of bones from Alaska showed high concentrations of nitrogen-15, a nitrogen isotope accumulated most strongly in carnivores. 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=":142" /> Based on this evidence, ''A.&nbsp;simus'' was suggested to have been more carnivorous in [[Beringia]] than the rest of North America (with a preference for herbivores which consumed [[C3 carbon fixation|C<sub>3</sub> vegetation]], particularly [[Reindeer|caribou]]).<ref name=":312" /><ref name=":412" /><ref>{{Cite journal |last=BOCHERENS |first=H |last2=EMSLIE |first2=S. D. |last3=BILLIOU |first3=D. |last4=MARIOTTI |first4=A. |date=1995 |title=Stables isotopes (13C, 15N) and paleodiet of the giant short-faced bear (Arctodus simus) |url=https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=3481071 |journal=Stables isotopes (13C, 15N) and paleodiet of the giant short-faced bear (Arctodus simus) |volume=320 |issue=8 |pages=779–784 |issn=1251-8050}}</ref> Increased carnivory may be due to a lower proportion of competitors and probably a lower availability of carbohydrate-rich food supplies across the year in the far northern latitudes.<ref name=":142" /> Survival during the cold season for some northern populations of ''A. simus'' 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_20102" /><ref name=":47" /> 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=":312" />

=== Carbon isotope studies ===
Although elevated nitrogen-15 levels have been argued to indicate carnivory, even the isotope data of the most carnivorous Beringian ''Arctodus'' overlapped with modern, typically [[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 omnivores which eat a significant amount of animal matter.<ref name=":110" /><ref name=":312" /> Studies are also complicated by a lack of compound-specific data,<ref name=":47" /> and isotope data being variable in carbon-13,<ref>{{Cite journal |last=Rawlence |first=Nicolas J. |last2=Wood |first2=Jamie R. |last3=Bocherens |first3=Herve |last4=Rogers |first4=Karyne M. |date=2016-06-15 |title=Dietary interpretations for extinct megafauna using coprolites, intestinal contents and stable isotopes: Complimentary or contradictory? |url=https://www.sciencedirect.com/science/article/pii/S0277379116301548 |journal=Quaternary Science Reviews |volume=142 |pages=173–178 |doi=10.1016/j.quascirev.2016.05.017 |issn=0277-3791}}</ref><ref name=":54">{{Cite journal |last=Kohn |first=Matthew J. |last2=McKay |first2=Moriah P. |date=2012-04-01 |title=Paleoecology of late Pleistocene–Holocene faunas of eastern and central Wyoming, USA, with implications for LGM climate models |url=https://www.sciencedirect.com/science/article/pii/S0031018212000612 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=326-328 |pages=42–53 |doi=10.1016/j.palaeo.2012.01.037 |issn=0031-0182}}</ref> and nitrogen-15 (due to individual/evolving prey and plant choices, the isotopic composition of the local environment, and nutritional stress).<ref name=":412" /><ref>{{Cite journal |last1=Fisher |first1=Daniel C. |last2=Cherney |first2=Michael D. |last3=Newton |first3=Cody |last4=Rountrey |first4=Adam N. |last5=Calamari |first5=Zachary T. |last6=Stucky |first6=Richard K. |last7=Lucking |first7=Carol |last8=Petrie |first8=Lesley |date=November 2014 |title=Taxonomic overview and tusk growth analyses of Ziegler Reservoir proboscideans |url=https://www.cambridge.org/core/journals/quaternary-research/article/abs/taxonomic-overview-and-tusk-growth-analyses-of-ziegler-reservoir-proboscideans/AF05EC53DB12810410A63CBD6A9FB6BD |journal=Quaternary Research |language=en |volume=82 |issue=3 |pages=518–532 |bibcode=2014QuRes..82..518F |doi=10.1016/j.yqres.2014.07.010 |issn=0033-5894 |s2cid=42376537}}</ref> [[Carbon-13]] levels in ''Arctodus simus'' (enriched by both plants and prey matter) consistently reflect a diet based on [[C3 carbon fixation|C<sub>3</sub> resources]], typically found in closed to mixed habitats with at least some tree cover (such as [[Woodland|open woodlands]]).<ref name=":232" /><ref name=":410" /><ref name=":31" /><ref name=":312" /><ref name=":47" /><ref name=":33" /> This includes C<sub>3</sub> vegetation ([[Leaf|leaves]], [[Plant stem|stems]], [[Mast (botany)|fruits]], [[Bark (botany)|bark]], and [[flower]]s from trees, shrubs, and cool season [[Poaceae|grasses]])<ref name=":132" /> and the browsers that fed on them, such as [[deer]], [[Camelidae|camelids]], [[Tapirus|tapir]], [[bison]] and [[ground sloth]]s.<ref name=":410" /><ref name="Figueiridio_et_al_20102" />
{| class="wikitable"
|+Studies
!Location
!Age
!Carbon 13 (δ13C)
!Nitrogen 15 (δ15N)
!Results
|-
|[[Fremont, California#Irvington District|Irvington]], California
|Early 
Pleistocene
|−14.5
|N/A
|''Arctodus simus'' carbon isotope values from Irvington (along with Fairmead Landfill and McKittrick Tar Pits) are consistent with diet based on [[C3 carbon fixation|C<sub>3</sub>]] resources.<ref name=":232" />
|-
|[[Madera County, California|Fairmead Landfill]], California
|Middle Pleistocene
|−11.9
|N/A
|Initially proposed to consume [[Columbian mammoth]], and large [[ungulate]]s,<ref name=":72">{{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> a 2015 study recalculated ''Arctodus''<nowiki/>' carbon isotope values to be closest to [[C3 carbon fixation|C<sub>3</sub> vegetation]] consuming deer and [[mastodon]].<ref name=":232" />
|-
|[[Cedral, San Luis Potosí|Cedral]], San Luis Potosí
|Late Pleistocene
|−11.8
|N/A
|This ''Arctodus'' individual had the strongest [[Δ13C|''δ''<sup>13</sup>C]] value of its local fauna. ''Arctodus''<nowiki/>' [[Carbon-13|carbon isotope]] value was closest to values from the [[Tapirus haysii|tapir]] and ''[[Hemiauchenia]]''.<ref name=":410" />
|-
|[[Natural Trap Cave]], Wyoming
|Late Pleistocene
| -13.1
|N/A
|The Natural Trap specimens have the lowest ''δ''<sup>13</sup>C of the Pleistocene fauna. Comparisons with contemporary ''Ursus'' suggest that the seasonality & individual choices within omnivorous diets could result in extreme isotope data, with each tooth not fully reflecting the total isotopic range consumed.<ref name=":54" />
|-
|[[Daisy Cave|Channel Islands]], California
|Late Pleistocene
| -17.9
|13.2
|Nitrogen isotope signatures suggested a ~19% consumption rate of [[pinniped|seal]]s (along with bison and camels). Fossil was likely transported post-mortem from the mainland; a partial reliance on marine resources has been suggested to be as a result of a competitive carnivore guild on mainland California. The marine signal was in between [[island fox]]es and [[bald eagle]]s, most closely resembling Late Pleistocene [[California condor]]s.<ref name=":47" />
|-
|[[McKittrick Tar Pits]], California
|Late Pleistocene
| -10.9
|N/A
|This carbon isotope value was closest to [[deer]], similar to the one inferred for the [[Cedral, San Luis Potosí|Cedral]] individual.<ref name=":410" /><ref name=":72" />
|-
|Little Box Elder Cave, Wyoming
|Late Pleistocene
| -14.9
|N/A
|Like Natural Trap Cave, the Little Box Elder Cave specimen had distinctly lower ''δ''<sup>13</sup>C levels, being only higher than ''Ursus''.<ref name=":54" />
|-
|[[San Antonio|Friesenhahn Cave]], Texas
|Late Pleistocene
| -16.5
|9.7
|The Friesenhahn Cave specimen had a nitrogen-15 sample closest to the omnivorous [[striped skunk]].<ref name=":33" />
|-
|[[Saanich Peninsula|Vancouver Island]], British Columbia
|Late Pleistocene
| -18.9
|10.6
|A specimen from Cowichan Head, Vancouver Island, had isotopes suggesting a terrestrial diet at a relatively high trophic level.<ref name=":31" />
|-
|[[Fairbanks North Star Borough, Alaska|Fairbanks]], Alaska
|Late Pleistocene
| -18.0
|8.4
|Nitrogen & carbon isotope data from several specimens suggests that ''Arctodus'' specialized on [[reindeer]] in central Alaska, both before and during the [[Last Glacial Maximum]].<ref name=":412" />
|-
|[[Dawson City|Dawson]], Yukon
|Late Pleistocene
| -18.5
|9.9
|''Arctodus''' [[Nitrogen 15|nitrogen-15]] levels are higher in the [[Yukon Plateau|Yukon]], suggesting a possibly even higher [[trophic level]] than other ''Arctodus'' in eastern Beringia. However, this contrast likely reflects subtle differences in the isotopic composition of [[Primary production|local plants]],<ref name=":402" /><ref>{{Cite journal |last1=Lanoë |first1=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 |journal=Quaternary Science Reviews |language=en |volume=175 |pages=85–96 |bibcode=2017QSRv..175...85L |doi=10.1016/j.quascirev.2017.10.003 |issn=0277-3791 |doi-access=free}}</ref> & [[muskox]] in the region, and possibly fellow predators and their kills, complimenting the consumption of reindeer.<ref name=":312" />
|}

== Hibernation ==
[[File:Fall_in_the_Ozarks.jpg|thumb|231x231px|''A. simus'' specimens have been particularly plentiful from caves in the [[Montane ecosystems#Montane forests|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]], such as the [[Ozarks]].|left]]
''Arctodus pristinus'' specimens have been found in caves such as [[Port Kennedy Bone Cave|Port Kennedy]], Pennsylvania (where fossils from as many as 36 individuals have been found), and [[Cumberland Bone Cave|Cumberland Cave]], Maryland, often in association with the black bear. This suggests a close association with the biome.<ref name=":5" /><ref name="researchgate.net">{{Cite journal |last1=Daeschler |first1=Edward B. |last2=Spamer |first2=Earl E. |last3=Parris |first3=David C. |date=1993 |title=Review and New Data on the Port Kennedy Local Fauna and Flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania |url=https://www.researchgate.net/publication/325630951 |journal=The Mosasaur - Delaware Valley Paleontological Society |volume=5 |pages=23–41 |via=ResearchGate}}</ref>

According to a 2003 study, in [[Karst|karst regions]], fossils of ''Arctodus simus'' have been recovered almost exclusively from cave sites.<ref name=":2" /> In the contiguous United States, that ~38% of all sites are from caves (possibly ~50% in western USA)<ref name=":44" /> suggests a close association between this species and cave environments. Cave passages produce numerous examples of small, yet relatively complete individuals. Taking into account that female bears are smaller and more prone to den in caves, it is likely that the majority of ''Arctodus simus'' from such deposits were females and may have been denning when they died.<ref name=":2" /> Although female specimens of ''Arctodus simus'' have been inferred to have been exhibiting maternal denning, 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 been 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 |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=33 |issue=3 |pages=211–222 |doi=10.1080/03115510902844418 |bibcode=2009Alch...33..211S |issn=0311-5518 |s2cid=55636895|url=http://sedici.unlp.edu.ar/handle/10915/5364 }}</ref>

At [[Riverbluff Cave]], the most abundant claw marks are from ''Arctodus simus''. They are most abundant at the bear beds and their associated passageways, indicating a close relationship with denning.<ref name=":1" /> 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]], [[Oklahoma]] and [[Shasta Lake|Potter Creek Cave]], California. These mixed deposits are assumed to have accumulated over time as individual bears (including ''Arctodus'') died during winter sleep.<ref name=":25" /><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 |url=https://www.researchgate.net/publication/324068143 |journal=Journal of Cave and Karst Studies |volume=80 |issue=2 |pages=1–16 |doi=10.4311/2017PA0118 |doi-access=free}}</ref><ref>{{Cite journal |last=Puckette |first=William L. |date=1976 |title=Notes on the occurrence of the short-faced bear (Arctodus) in Oklahoma |journal=Proceedings of the Oklahoma Academy of Science |volume=56 |pages=67–68|citeseerx=10.1.1.605.3584 }}</ref> Furthermore, [[environmental DNA]] suggests that ''Arctodus'' and black bears shared a cave in [[Chiquihuite cave]], Zacatecas.<ref name="Pedersen 2728–2736.e8" /> At [[Schell Creek Range|Labor-of-Love cave]], Nevada, both American black bears and 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]], Wyoming and [[Fairbanks North Star Borough, Alaska|Fairbanks II]], Alaska hosting similar remains.<ref name=":132" /><ref name=":362" />

== Paleoecology ==
=== ''Arctodus pristinus'' ===
[[File:South Florida Museum - Big Carnivore Skeleton.jpg|thumb|A reconstruction of ''Arctodus pristinus'', from the [[Bishop Museum of Science and Nature]], Florida.]]Although smaller than its descendant, ''Arctodus pristinus'' was still a relatively large tremarctine bear.<ref name=":262" /> Sometimes referred to as the eastern short-faced bear,<ref>{{Cite book |last=Grumet |first=Robert S. |title=Bay, Plain, and Piedmont- A Landscape History of the Chesapeake Heartland from 1.3 Billion Years Ago to 2000 |date=September 2000 |publisher=The Chesapeake Bay Heritage Context Project |pages=16, 21, 167}}</ref> ''A. pristinus'' has been found in Florida,<ref name=":5" /> Kansas,<ref name=":8" /> Maryland,<ref name=":8" /> New Mexico,<ref>{{Cite journal |last1=Morgan |first1=Gary S. |last2=Lucas |first2=Spencer G. |date=2005 |title=Pleistocene vertebrate faunas in New Mexico from alluvial, fluvial, and lacustrine deposits |url=https://www.researchgate.net/publication/281207462 |journal=New Mexico Museum of Natural History and Science Bulletin |volume=28 |pages=207}}</ref> Pennsylvania,<ref name=":44" />'''<ref name="researchgate.net" />''' South Carolina,<ref name=":45">{{Cite journal |last1=Albright |first1=L. Barry |last2=Sanders |first2=Albert |last3=Weems |first3=Robert |last4=Cicimurri |first4=David |last5=Knight |first5=James |date=2020-01-24 |title=Cenozoic Vertebrate Biostratigraphy of South Carolina, USA, and Additions to the Fauna |url=https://digitalcommons.unf.edu/facultyshowcase/2020/Showcase/1 |journal=Showcase of Faculty Scholarly & Creative Activity}}</ref> and West Virginia in the US,<ref name=":8" /> and [[Aguascalientes]] in 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>''' Possible remains have also been recovered from Arizona.<ref name=":8" /><ref name=":210">{{Cite journal |last1=White Jr. |first1=Richard S. |last2=Morgan |first2=Gary S. |date=2005 |title=Arizonan Blancan Vertebrate Faunas in Regional Perspective |url=https://www.researchgate.net/publication/267844516 |journal=Vertebrate Paleontology of Arizona, Mesa Southwest Museum Bulletin |volume=11}}</ref> ''A. pristinus'' is particularly well known from Florida, especially from the Leisey Shell Pit.<ref>{{Cite journal |last=Berta |first=Annalisa |date=1995 |title=Fossil carnivores from the Leisley Shell Pit, Hillsborough County, Florida |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-14.pdf |journal=Bulletin of the Florida Museum of Natural History |volume=37 Part II |issue=14 |pages=436–499}}</ref> Like ''A. simus'' and other tremarctine bears, ''A. pristinus'' had adaptations for herbivory, and was likely largely herbivorous itself,<ref name=":5" /> although ''Arctodus'' has been suggested to be generally more carnivorous than contemporary bears.<ref name=":262" /><ref name=":30" />

==== Eastern North America ====
''Arctodus pristinus'' is considered a [[Biochronology|biochronological]] indicator for the period between the Late Blancan and late Irvingtonian periods of Pleistocene Florida- more fossils of ''Arctodus pristinus'' are known from Florida (about 150) than anywhere else.<ref name=":5" /> In the [[Gelasian|Early Pleistocene]] of [[Blancan]] Florida, the [[Santa Fe River (Florida)|Santa Fe River 1 site]] (~2.2 Ma), which ''Arctodus pristinus'' inhabited,<ref name=":262" /><ref name=":5" /> was a fairly [[Savanna|open grassland]] environment dotted with [[Karst|karst sinks]] and [[Spring (hydrology)|springs]] and dominated by [[Flatwoods|longleaf pine flatwoods]]. ''Arctodus pristinus'' co-existed with [[Titanis|terror birds]], [[Xenosmilus|sabertooth cats]], giant sloths (''[[Eremotherium]]'', ''[[Megalonyx]]'', ''[[Paramylodon]]''), giant armadillos (''[[Glyptotherium]],'' ''[[Holmesina]]'', ''[[Pachyarmatherium]]''), [[Rhynchotherium|gomphotheres]], [[Chasmaporthetes|hyenas]], canids (''[[Borophagus]]'', ''[[Canis lepophagus]]''), [[Platygonus|peccaries]], [[Hemiauchenia|llamas]], [[Capromeryx|dwarf pronghorns]], and [[Nannippus|three-toed horses]]. Smaller fauna included [[condor]]s, [[Rail (bird)|rails]], [[duck]]s, [[Erethizon|porcupines]], and alligators.<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 |bibcode=2007Geo....35..123M |doi=10.1130/G23186A.1}}</ref>

=== ''Arctodus simus'' ===
{{Multiple image
| image1            = Nearctic-Ecozone-Biocountries-2-IM.svg
| image2            = Physiographic Subdivisions of the Contiguous United States.jpg
| direction         = vertical
| caption2          = By the [[Late Pleistocene]], ''Arctodus simus'' was present in most physiographic regions of the [[Nearctic realm]].
| align             = right
}}
Evolving from the smaller ''A. pristinus'' around 1.36 million 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_20102" /><ref name=":302" /><ref name=":156" /><ref name=":47" /><ref name=":52" /> If ''Arctodus simus'' wasn't largely herbivorous,<ref name=":5" /><ref name=":132" /> 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_20102" /><ref name=":110" /><ref name=":156" /><ref name=":53">{{Cite journal |last1=Domínguez-Rodrigo |first1=Manuel |last2=Egeland |first2=Charles P. |last3=Cobo-Sánchez |first3=Lucía |last4=Baquedano |first4=Enrique |last5=Hulbert |first5=Richard C. |date=2022-05-02 |title=Sabertooth carcass consumption behavior and the dynamics of Pleistocene large carnivoran guilds |journal=Scientific Reports |language=en |volume=12 |issue=1 |pages=6045 |doi=10.1038/s41598-022-09480-7 |issn=2045-2322|doi-access=free |pmid=35501323 |pmc=9061710 |bibcode=2022NatSR..12.6045D }}</ref>

Primarily inhabiting a range from southern Canada to [[Puebla|central Mexico]] in the west, to Pennsylvania and Florida in the east,<ref name=":8" /><ref name=":02" /><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 |bibcode=2014JQS....29..515H |doi=10.1002/jqs.2724 |s2cid=18644154}}</ref> ''A. simus'' also inhabited [[Beringia]] between ~50,000 BP and ~23,000 BP. Finds today span from northern [[Alaska]] to the [[Yukon]].<ref name="Pedersen 2728–2736.e8" /><ref name=":02" /><ref name=":24" /> Based on the wide distribution of the species, ''Arctodus simus'' inhabited a diversity of climatic conditions and environments,<ref name=":02" /><ref name=":132" /><ref name=":142" /> ranging from [[Taiga|boreal forests]] and moist [[tundra]] in the north,<ref name=":19" /> the [[Montane ecosystems#Montane forests|montane woodlands]] of the [[U.S. Interior Highlands|US Interior Highlands]],<ref name=":92" /> the [[pluvial lake]]s and [[Pinyon–juniper woodland|piñon–juniper woodland]] of the [[Intermontane Plateaus|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 |bibcode=2006QSRv...25.2964G |doi=10.1016/j.quascirev.2006.03.004 |issn=0277-3791}}</ref> [[Subtropics|subtropical]] [[woodland]]s and [[savanna|mixed savanna]]s of the [[Sun Belt|southern USA]] and [[Mexican Plateau]],<ref name=":10" /><ref name=":232" /><ref name=":410" /> 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=":352" /> A 2009 study examining megafaunal extinctions in [[Northern America]] noted 12 records of ''Arctodus simus'' (<40,000 BP) from the [[Intermontane Plateaus]], 7 from the [[Pacific Mountain System]], 6 each from the [[Interior Plains]] and [[U.S. Interior Highlands|Interior Highlands]], 3 from the [[Atlantic Plain]]s and 1 from the [[Appalachian Highlands]].<ref name=":51" />

Sometimes referred to as the bulldog bear,<ref>{{Cite journal |last=Legge |first=A. J. |date=March 1991 |title=Where ends meat |url=https://www.cambridge.org/core/journals/antiquity/article/abs/where-ends-meat/21B26626DA3AC3377EDF5CEB58A6D64A |journal=Antiquity |language=en |volume=65 |issue=246 |pages=147–153 |doi=10.1017/S0003598X00079424 |issn=0003-598X |s2cid=163458417}}</ref><ref name=":0">{{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> or great short-faced bear,<ref name="evolution" /><ref>{{Cite web |title=great short-faced bear fossil |url=https://www.backyardnature.net/loess/~s-fbear.htm |access-date=2023-10-23 |website=www.backyardnature.net}}</ref> ''Arctodus simus'' has been recovered from a comparatively small number of finds in relation to other large carnivorans, with the species suggested to have lived in low population densities.<ref name="Pedersen 2728–2736.e8" /> However, ''A. simus'' was relatively plentiful in western North America, with over 50% of specimens from the contiguous United States (<40,000 BP).<ref name=":92" /><ref name=":142" /> ''Arctodus simus'' was integral to what has been referred to as the ''[[Camelops]]'' fauna, or alternatively ''Camelops''/''[[American mountain deer|"Navahoceros"]]'' fauna, a faunal province centered in western North America. The ''Camelops'' fauna was also characterized by [[Euceratherium|shrub-ox]], [[prairie dog]]s, [[Capromeryx|dwarf pronghorns]], [[Nothrotheriops|Shasta ground sloths]], and [[American lion]]s. The diverse flora of the ''Camelops'' faunal province included montane conifers and oak parklands, shrub and grassland that stretched across the [[North American Cordillera]] south of Canada, to the [[Valley of Mexico]]. This faunal province supported a variety of large grazing and browsing mammals.<ref name=":9" /><ref>{{Cite journal |last=Pichardo |first=Mario |date=2003 |title=Overview of Central Mexican Prehistory: Morphostratigraphy, Chronostratigraphy, Biostratigraphy |journal=Anthropologischer Anzeiger |volume=61 |issue=2 |pages=141–174 |doi=10.1127/anthranz/61/2003/141 |issn=0003-5548 |jstor=29542453 |pmid=12872543}}</ref><ref>{{Cite web |title=KGS--Guidebook 5--Wisconsinan Mammalian Faunas |url=https://www.kgs.ku.edu/Publications/Bulletins/GB5/Martin2/ |access-date=2022-08-01 |website=www.kgs.ku.edu}}</ref> Matheus argues that unlike other [[Holarctic realm|Holoarctic]] carnivorans, ''A. simus'' did not appear to have an ecological equivalent ("super-huge bear") in the [[Palearctic realm]].<ref name=":36" />

==== Pacific Mountain System ====
[[File:North Slope Santa Ynez Mtns.jpg|thumb|''Arctodus simus'' inhabited [[California chaparral and woodlands|Californian savannas]] for over a million years.|left]]The [[Pacific Mountain System]] seems to represent a cradle of evolution for ''Arctodus simus''. The earliest finds of ''Arctodus simus'' are from California, from early and middle [[Irvingtonian]] age sites such as [[Fairmead, California|Fairmead]],<ref>{{Cite book |last1=Dundas |first1=Robert G. |last2=Chatters |first2=James C. |title=Geologic Excursions from Fresno, California, and the Central Valley: A Tour of California's Iconic Geology |date=2013-01-01 |chapter=The mid-Irvingtonian Fairmead Landfill fossil site, Madera County Paleontology Collection, and Fossil Discovery Center of Madera County, California |editor=Keith Putirka |pages=63–78 |publisher=Geological Society of America |language=en |doi=10.1130/2013.0032(04)|isbn=978-0-8137-0032-8 }}</ref> [[Fremont, California#Irvington District|Irvington]],<ref>{{Cite book |last=Firby |first=Jean Brower |url=https://books.google.com/books?id=qOdKAQAAMAAJ |title=Revision of the Middle Pleistocene Irvington Fauna of California |date=1968 |publisher=University of California |language=en}}</ref> [[Murrieta, California|Riverside County]],<ref name=":46" /> and [[Vallecito Creek (California)|Vallecito Creek]].<ref>{{Cite journal |last=Cassiliano |first=Michael L. |date=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 |jstor=4523978 |issn=0272-4634}}</ref>

Despite the shift to aridified environments from the Early to Late Pleistocene of the [[Central Valley (California)|Central Valley]] (1.1Ma to ~15,000 BP), ''Arctodus simus'' remained consistent with the consumption of C<sub>3</sub> resources. This period saw the evolution from wetter mixed woodland-grassland and marsh/prairie C<sub>3</sub> dominated environs at Irvington and Fairmead, to the more arid, mixed C<sub>3</sub>-C<sub>4</sub> savannas of the [[McKittrick Tar Pits]]. [[dire wolf|Dire wolves]] and ''Arctodus simus'' were consistent members of the local predator guild throughout the Pleistocene, whereas [[jaguar]]s, ''[[Homotherium]]'', ''[[Miracinonyx]]'' and ''[[Smilodon]]'' transitioned to ''Panthera atrox'' and [[coyote]]s.<ref name=":232" /> In addition to browsing, ''Arctodus'' could have competed with other closed habitat browser specialists such as ''Smilodon'' and ''Panthera atrox'' for deer ([[Elk|''Cervus'']] & ''[[Odocoileus]]''), camelids (''Hemiauchenia'' & ''Camelops''), ''Paramylodon'', and [[Platygonus|peccaries]].<ref name=":232" /> However, specimens collected from the [[La Brea Tar Pits]] show evidence that ''A. simus'' preferred a herbivorous diet. ''A. simus'' is particularly famous from fossils found in the La Brea Tar Pits, with 33 individuals recovered (the most of any locality).<ref>{{Cite book |url=https://tarpits.org/sites/default/files/2019-04/tar_pits_fossil_count.pdf |title=Tar Pits Fossil Count |publisher=La Brea Tar Pits and Museum}}</ref><ref name="Donohue2" /><ref>{{Cite journal |last1=Carbone |first1=Chris |last2=Maddox |first2=Tom |last3=Funston |first3=Paul J. |last4=Mills |first4=Michael G.L. |last5=Grether |first5=Gregory F. |last6=Van Valkenburgh |first6=Blaire |date=2009-02-23 |title=Parallels between playbacks and Pleistocene tar seeps suggest sociality in an extinct sabretooth cat, Smilodon |journal=Biology Letters |volume=5 |issue=1 |pages=81–85 |doi=10.1098/rsbl.2008.0526 |issn=1744-9561 |pmc=2657756 |pmid=18957359}}</ref> As only one juvenile has been found from La Brea, ''A. simus'' is suggested to have been solitary.<ref name=":53" /> Many more finds come from across California,<ref name=":8" /><ref name=":25" /> Vancouver Island,<ref name=":156" /><ref name=":31">{{Cite journal |last1=Steffen |first1=Martina L. |last2=Harington |first2=C. R. Harington |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/10.1139/E10-018 |journal=Canadian Journal of Earth Sciences |language=en |volume=47 |issue=8 |pages=1029–1036 |bibcode=2010CaJES..47.1029S |doi=10.1139/E10-018 |archive-url=}}</ref>  and [[Washington (state)|Washington]],<ref name=":31" /> where the semi-arid woodland/scrub transitioned to [[Forest steppe|forest-steppe]],<ref name=":472" /> and open grasslands/heath.<ref name=":31" />

Comparatively, the [[Rocky Mountain System]] had the fewest number of specimens of ''Arctodus simus'' in western North America.<ref name=":92" /> However, one of the youngest dated ''Arctodus simus'' is from a cave near Huntington Reservoir, Utah, which sits at an elevation of 2,740m (~9,000&nbsp;ft). The central and southern Rocky Mountains may have acted as refugia for boreal parkland megafauna from the plateau such as ''Arctodus simus'',<ref name=":382" /><ref name=":9" /> with the Huntington specimen being the only confirmed extinct megafauna dated to the [[Younger Dryas]] of the [[Great Basin]].<ref name=":55">{{Cite journal |last=Goebel |first=Ted |last2=Hockett |first2=Bryan |last3=Adams |first3=Kenneth D. |last4=Rhode |first4=David |last5=Graf |first5=Kelly |date=2011-10-15 |title=Climate, environment, and humans in North America’s Great Basin during the Younger Dryas, 12,900–11,600 calendar years ago |url=https://www.sciencedirect.com/science/article/pii/S1040618211001893 |journal=Quaternary International |series=HUMANS AND YOUNGER DRYAS: DEAD END, SHORT DETOUR, OR OPEN ROAD TO THE HOLOCENE? |volume=242 |issue=2 |pages=479–501 |doi=10.1016/j.quaint.2011.03.043 |issn=1040-6182}}</ref> Other remains have been found from Wyoming (such as [[Natural Trap Cave]]),<ref>{{Cite journal |last=Long |first=C. A. |date=1971 |title=Significance of the Late Pleistocene fauna from the Little Box Elder Cave, Wyoming, to studies of zoogeography of recent mammals |journal=Great Basin Naturalist |language=en |volume=31 |issue=2 |s2cid=55933331 |article-number=11}}</ref><ref>{{Cite journal |last=Walker |first=Danny N. |date=1987 |title=Late Pleistocene/Holocene Environmental Changes in Wyoming: the Mammalian Record |url=https://www.uwyo.edu/anthropology/_files/docs/walker/26%20walker%201987%20environmental%20summary.pdf |journal=Office of the Wyoming State Archeologist}}</ref> and Montana.<ref>{{Cite journal |last1=Smith |first1=Larry N. |last2=Hill |first2=Christopher L. |last3=Reiten |first3=Jon |title=Quaternary and Late Tertiary of Montana: Climate, Glaciation, Stratigraphy, and Vertebrate Fossils |url=https://mbmg.mtech.edu/pdf/geologyvolume/Smith_QuaternaryMontanaFinal.pdf |journal=Montana Bureau of Mines and Geology Publication 122 |volume=1: Geologic History |via=Montana Bureau of Mines and Geology}}</ref><ref>{{Cite journal |last=Hill |first=Christopher L. |date=2006-01-01 |title=Stratigraphic and geochronologic contexts of mammoth (Mammuthus) and other Pleistocene fauna, Upper Missouri Basin (northern Great Plains and Rocky Mountains), U.S.A. |url=https://www.sciencedirect.com/science/article/pii/S104061820500056X |journal=Quaternary International |series=Third International Mammoth Conference, Dawson, Yukon |language=en |volume=142-143 |pages=87–106 |doi=10.1016/j.quaint.2005.03.007 |bibcode=2006QuInt.142...87H |issn=1040-6182}}</ref>

==== Intermontane Plateaus ====
[[File:Paleontological_landscape_painting,_White_Sands_National_Park,_United_States.jpg|thumb|A reconstruction of Rancholabrean New Mexico ([[White Sands National Park|White Sands]]).|left]]The [[Intermontane Plateaus]] had the highest number of ''Arctodus simus'' specimens south of the ice sheets.<ref name=":92" /><ref name=":51" /> The region has yielded some of the largest specimens of ''A. simus,'' including, what was once the largest specimen on record, from Salt Lake Valley, Utah.<ref name=":6" /> In contrast with other parts of North America, the [[Intermountain West|plateaus]] received more rainfall during the Late Pleistocene, as glacially cooled air collided with hot desert air. As a result, this greatly expanded the range of subalpine parkland, [[Pinyon–juniper woodland|piñon-juniper]] & [[Ponderosa pine forest|ponderosa woodlands]], [[Sagebrush steppe|sagebrush grasslands]] and [[pluvial lake]]s where desert exists today.<ref name=":55" /><ref name=":472" /><ref name=":44" /> The mid-[[Wisconsin glaciation|Wisconsian]] U-Bar Cave, New Mexico, was vegetated by [[Artemisia tridentata|sagebrush]], grasses, and woodlands. Notable fauna which lived alongside ''Arctodus simus'' included Shasta ground sloth, [[Euceratherium|shrub-ox]], pronghorns (''Stockoceros,'' ''Capromeryx''), ''Camelops'', ''Odocoileus'', horses, ''Lynx'', [[Cougar|puma]], black bear, [[Oreamnos|mountain goats]]'','' prairie dogs, and [[Stock's vampire bat]].<ref name=":27">{{Cite journal |last=Harris |first=Arthur H. |date=November 1985 |title=Preliminary report on the vertebrate fauna of U-Bar Gave, Hidalgo County, New Mexico |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/7/n4/nmg_v7_n4_p74.pdf |journal=New Mexico Geology |volume=7 |issue=4 |pages=74–84|doi=10.58799/NMG-v7n4.74 |s2cid=237056633 }}</ref><ref>{{Cite web |title=U-Bar Cave |url=https://www.utep.edu/leb/pleistnm/sites/ubarcave.htm |access-date=2022-07-24 |website=www.utep.edu}}</ref> Dire wolves were also found in association with ''Arctodus simus,'' and both species are the most common large carnivorans of Rancholabrean New Mexico.<ref name=":44" /> Beyond Utah and New Mexico,<ref name=":44" /><ref>{{Cite journal |last1=Schultz |first1=C. Bertrand |last2=Howard |first2=Edgar B. |last3=Schultz |first3=C. Bernard |date=1935 |title=The Fauna of Burnet Cave, Guadalupe Mountains, New Mexico |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=87 |pages=273–298 |jstor=4064215 |issn=0097-3157}}</ref><ref>{{Cite journal |last=Harris |first=Arthur H. |date=1993 |title=Quaternary Vertebrates of New Mexico |url=https://www.utep.edu/leb/curators/QuatVert.pdf |journal=Vertebrate Paleontology in New Mexico, New Mexico Museum of Natural History and Science |volume=Bulletin 2 |pages=179–197}}</ref><ref>{{Cite journal |last1=Harris |first1=A. H. |last2=Findley |first2=J. S. |date=1964-01-01 |title=Pleistocene-Recent fauna of the Isleta caves, Bernalillo County, New Mexico |journal=American Journal of Science |language=en |volume=262 |issue=1 |pages=114–120 |doi=10.2475/ajs.262.1.114 |bibcode=1964AmJS..262..114H |issn=0002-9599|doi-access=free }}</ref><ref>{{Cite conference |last1=Morgan |first1=Gary S. |last2=Lucas |first2=Spencer G. |last3=Love |first3=David |date=2009 |title=Cenozoic vertebrates from Socorro County, central New Mexico |editor=Virgil Lueth |editor2=Spencer G. Lucas |editor3=Richard M. Chamberlin |book-title=New Mexico Geological Society Fall Field Conference Guidebook: 60 Geology of the Chupadera Mesa |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/60/60_p0321_p0336.pdf |pages=321–336}}</ref><ref>{{Cite journal |last1=Morgan |first1=Gary S. |last2=Lucs |first2=Spencer G. |date=2005-01-01 |title=Pleistocene vertebrates from southeastern New Mexico |url=https://digitalcommons.usf.edu/kip_articles/4347 |journal=KIP Articles}}</ref> other important US specimens have also been found in Arizona,<ref name=":8" /> eastern California,<ref>{{Cite journal |last1=Springer |first1=Kathleen |last2=Scott |first2=Eric |last3=Murray |first3=Lyndon K. |last4=Sagebiel |first4=James |date=2009 |title=The Diamond Valley Lake local fauna: late Pleistocene vertebrates from inland southern California |editor=Albright, L. B. III |journal=Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne |url=https://www.academia.edu/218818}}</ref> Idaho,<ref name=":8" /> Nevada,<ref>{{Cite journal |last1=Emslie |first1=Steven D. |last2=Mead |first2=Jim I. |date=August 2020 |title=The Age and Vertebrate Paleontology of Labor-of-Love Cave, White Pine County, Nevada |url=https://bioone.org/journals/western-north-american-naturalist/volume-80/issue-3/064.080.0301/The-Age-and-Vertebrate-Paleontology-of-Labor-of-Love-Cave/10.3398/064.080.0301.full |journal=Western North American Naturalist |volume=80 |issue=3 |pages=277–291 |doi=10.3398/064.080.0301 |s2cid=225958789 |issn=1527-0904}}</ref> and eastern [[Fossil Lake (Oregon)|Oregon]].<ref>{{Cite web  |title=LATE PLEISTOCENE AIRPORT LANE FOSSIL SITE, LA GRANDE ... |url=https://www.yumpu.com/en/document/view/12116022/late-pleistocene-airport-lane-fossil-site-la-grande- |access-date=2022-07-17 |website=yumpu.com |language=en}}</ref><ref>{{Cite journal |last1=Van Tassell |first1=Jay |last2=Rinehart |first2=John |last3=Mahrt |first3=Laura |date=June 2014 |title=Late Pleistocene Airport Lane fossil site, La Grande, northeast Oregon |url=https://www.oregongeology.org/pubs/OG/OGv70n01_print.pdf |journal=Oregon Geology |volume=70 |issue=1 |pages=3–13 |via=Oregon Department of Geology and Mineral Studies}}</ref><ref>{{Cite web |title=The Spokesman-Review - Google News Archive Search |url=https://news.google.com/newspapers?nid=1314&dat=19280626&id=PGpWAAAAIBAJ&sjid=vvMDAAAAIBAJ&pg=5453,5034598 |access-date=2022-07-20 |website=news.google.com}}</ref>

The Intermontane Plateaus extended deep into Mexico, where tremarctine bears (''Arctodus simus &'' ''[[Tremarctos floridanus]]'') were dominant.<ref name=":92" /> ''Arctodus simus'' was limited to the [[Mexican Plateau|Mexican plateau]], which was generally occupied by tropical thorn scrub and scrub woodland.<ref name=":373">{{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><ref name=":472">{{Cite journal |last1=University of Geneva, Switzerland |last2=Ray |first2=N. |last3=Adams |first3=J.M. |date=2001 |title=A GIS-based Vegetation Map of the World at the Last Glacial Maximum (25,000-15,000 BP) |url=http://intarch.ac.uk/journal/issue11/rayadams_index.html |journal=Internet Archaeology |issue=11 |doi=10.11141/ia.11.2}}</ref> An ''Arctodus simus'' individual from [[Cedral, San Luis Potosí|Cedral]], San Luis Potosí, inhabited closed vegetation, based on the individual's [[Δ13C|''δ''<sup>13</sup>C]] signature. Consuming C<sub>3</sub> resources, its diet may have incorporated local C<sub>3</sub> specialists such as [[tapir]], [[Hemiauchenia|llamas]], [[Camelops|camels]], and [[Nothrotheriops|Shasta ground sloth]] along with browsed vegetation. The site, incorporating trees, herbs and cacti, hosted an open [[gallery forest]] near [[Savanna|grassland]] or [[Shrubland|scrub]] with a [[Humid subtropical climate|humid climate]]. This biodiverse [[Savanna|forest-savanna mosaic]] was part of the wider [[Mesic habitat|mesic]] savanna and [[Pinyon–juniper woodland|piñon–juniper woodland]] ecoregion which ''Arctodus'' inhabited in the [[Late Pleistocene]] [[Mexican Plateau|central Mexico]] and [[Southwestern United States|southwestern USA]].<ref name=":410" /><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> Similar highland remains have been recovered from [[Zacoalco de Torres|Jalisco]],<ref>{{Cite journal |last=Lucas |first=Spencer G. |date=January 2008 |title=Late Pleistocene Vertebrate Fossil Assemblages From Jalisco, Mexico |url=https://www.researchgate.net/publication/281862788 |journal=Neogene Mammals. New Mexico Museum of Natural History and Science |volume=Bulletin 44 |pages=51–64 |via=ResearchGate}}</ref> [[Lake Cuitzeo|Michoacán]],<ref name=":373" /> [[Hueyatlaco|Puebla]],<ref name=":8" /> [[Tequixquiac|State of Mexico]],<ref>{{Cite journal |last=Hibbard |first=Claude W. |date=18 February 1955 |title=Pleistocene Vertebrates from the Upper Becerra (Becerra Superior) Formation, Valley of Tequixquiac, Mexico, with Notes on Other Pleistocene Forms |journal=Contributions from the Museum of Paleontology |volume=XII |issue=5 |pages=47–96 |hdl=2027.42/48290 |url=http://deepblue.lib.umich.edu/handle/2027.42/48290 |language=en-US}}</ref><ref>{{cite journal |last1=Carranza-Castañeda |first1=Oscar |last2=Miller |first2=Wade E. |date=16 September 1987 |title=Rediscovered type specimens and other important published Pleistocene mammalian fossils from Central Mexico |journal=Journal of Vertebrate Paleontology |volume=7 |issue=3 |pages=335–341 |bibcode=1987JVPal...7..335C |doi=10.1080/02724634.1987.10011664}}</ref> and [[Chiquihuite cave|Zacatecas]].<ref name="Pedersen 2728–2736.e8" />

==== Interior Plains ====
The [[Interior Plains]] were composed of temperate steppe grassland,<ref name=":472" /> and among the specimens yielded from this region is one of the largest ''Arctodus simus'' currently on record, from the banks of the Kansas river.<ref>{{Cite journal |last1=Gobetz |first1=Katrina E. |last2=Martin |first2=Larry D. |date=2001 |title=An Exceptionally Large Short-faced Bear (Arctodus simus) from the Late Pleistocene(?) /Early Holocene of Kansas |url=https://liberalarts.tamu.edu/csfa/wp-content/uploads/sites/14/2023/07/CRP-18-2001.pdf |journal=Current Research in the Pleistocene |volume=18 |pages=97–99 |issn=8755-898X}}</ref> The late Irvingtonian [[Miles City, Montana|Doeden gravel pits]] in Montana preserves an open grassland habitat, with riparian woodlands, and likely some shrublands.<ref>{{Cite web |title=Abstract: PLEISTOCENE VERTEBRATES FROM THE DOEDEN LOCAL FAUNA (ILLINOIAN/SANGAMONIAN?), YELLOWSTONE RIVER VALLEY, EASTERN MONTANA (Rocky Mountain - 55th Annual Meeting (May 7-9, 2003)) |url=https://gsa.confex.com/gsa/2003RM/webprogram/Paper53111.html |access-date=2022-07-20 |website=gsa.confex.com}}</ref> ''Arctodus simus'' co-existed with ground sloths (''[[Megalonyx]]'', ''Paramylodon''), Pacific [[mastodon]], [[Camelops|camels]], and ''[[Bootherium]]''.<ref>{{Cite journal |last1=McDonald |first1=Andrew T. |last2=Atwater |first2=Amy L. |last3=Dooley Jr |first3=Alton C. |last4=Hohman |first4=Charlotte J.H. |date=2020-11-16 |title=The easternmost occurrence of Mammut pacificus (Proboscidea: Mammutidae), based on a partial skull from eastern Montana, USA  |journal=PeerJ |volume=8 |pages=e10030 |doi=10.7717/peerj.10030 |issn=2167-8359 |pmc=7676352 |pmid=33240588 |doi-access=free }}</ref><ref>{{Cite journal |last1=Hill |first1=Christopher L |last2=Wilson |first2=Michael C |date=2002 |title=Fossil Arctodus from the Doeden Local Fauna (Illinoian/Sangamonian?), Eastern Montana |url=https://www.researchgate.net/publication/270216214 |journal=Unknown |via=ResearchGate}}</ref><ref name=":4">{{Cite journal |last1=Hill |first1=Christopher L. |last2=Wilson |first2=Mike C. |date=2000 |title=The Doeden Local Fauna (Illinoian/Sangamonian?), Eastern Montana |url=https://www.researchgate.net/publication/270216333 |journal=Unknown |pages=140–142 |via=ResearchGate}}</ref> As bison were yet to migrate into North America, [[Columbian mammoth]]s and horses dominated these [[Illinoian (stage)|early Illinoian]] grasslands.<ref>{{Cite journal |last1=Froese |first1=Duane |last2=Stiller |first2=Mathias |last3=Heintzman |first3=Peter D. |last4=Reyes |first4=Alberto V. |last5=Zazula |first5=Grant D. |last6=Soares |first6=André E. R. |last7=Meyer |first7=Matthias |last8=Hall |first8=Elizabeth |last9=Jensen |first9=Britta J. L. |last10=Arnold |first10=Lee J. |last11=MacPhee |first11=Ross D. E. |date=2017-03-28 |title=Fossil and genomic evidence constrains the timing of bison arrival in North America |journal=Proceedings of the National Academy of Sciences |language=en |volume=114 |issue=13 |pages=3457–3462 |doi=10.1073/pnas.1620754114 |issn=0027-8424 |pmc=5380047 |pmid=28289222|bibcode=2017PNAS..114.3457F |doi-access=free }}</ref>[[File:Wildflowers on ranchland, State Highway 965, Llano County, Texas, USA (13 April 2012).jpg|thumb|221x221px|''Arctodus'' also roamed the [[Texas Blackland Prairies|southern mixed grasslands]] of Texas.|left]]In the [[Rancholabrean]] age, ''Arctodus simus'', grey wolves and coyotes were part of a predator guild throughout the great plains, and were joined by [[Columbian mammoth]]s, camels, ''Hemiauchenia'', and American pronghorns. While the northern plains aridified into cold steppe (e.g. [[The Mammoth Site|Mammoth site]], South Dakota),<ref name=":242">{{Cite journal |last=Louguet-Lefebvre |first=Sophie |date=2013-12-15 |title=The Columbian mammoths from the Upper Pleistocene of Hot Springs (South Dakota, United States) |url=https://journals.openedition.org/paleo/2861 |journal=PALEO. Revue d'archéologie préhistorique |language=en |issue=24 |pages=149–171 |doi=10.4000/paleo.2861 |issn=1145-3370|doi-access=free }}</ref> the southern plains were a parkland with riparian [[Celtis|hackberry]] forests, and large expanses of mixed grass prairie grasslands grading into [[wet meadow]]s, with limited seasonality. In the south ([[Lubbock Lake Landmark|Lubbock Lake]], Texas), this fauna was joined by ''[[Smilodon]]'', [[dire wolf|dire wolves]], grey fox and red fox, preying upon prairie dogs, horses (''Equus'' & ''[[Haringtonhippus]]''), peccaries, ''Odocoileus'', ''Capromeryx'', ''Bison antiquus'' and ''Holmesina''.<ref name=":242" /><ref name=":252">{{Cite journal |last=Johnson |first=Eileen |date=1986 |title=Late Pleistocene and Early Holocene Vertebrates and Paleoenvironments on the Southern High Plains, U.S.A. |url=https://www.erudit.org/en/journals/gpq/1900-v1-n1-gpq1924/032647ar.pdf |journal=Géographie physique et Quaternaire |volume=40 |issue=3 |pages=249–261 |doi=10.7202/032647ar}}</ref> Beyond Texas,<ref>{{Cite journal |last1=Smith |first1=Felisa A. |last2=Tomé |first2=Catalina P. |last3=Elliott Smith |first3=Emma A. |last4=Lyons |first4=S. Kathleen |last5=Newsome |first5=Seth D. |last6=Stafford |first6=Thomas W. |date=February 2016 |title=Unraveling the consequences of the terminal Pleistocene megafauna extinction on mammal community assembly |url=https://onlinelibrary.wiley.com/doi/10.1111/ecog.01779 |journal=Ecography |language=en |volume=39 |issue=2 |pages=223–239 |doi=10.1111/ecog.01779 |bibcode=2016Ecogr..39..223S |s2cid=4823663 |issn=0906-7590}}</ref> ''Arctodus'' has also been found in Iowa,<ref>{{Cite web |title=Giant Short-Faced Bear {{!}} University of Iowa Museum of Natural History - The University of Iowa |url=https://mnh.uiowa.edu/giant-short-faced-bear |access-date=2022-07-18 |website=mnh.uiowa.edu |language=en}}</ref> Kansas,<ref name=":8" /><ref>{{Cite journal |last=Taylor |first=D. W. |date=1960 |title=Late Cenozoic molluscan faunas from the High Plains |url=https://pubs.er.usgs.gov/publication/pp337 |journal=Professional Paper |doi=10.3133/pp337 |issn=2330-7102|doi-access=free }}</ref> Nebraska,<ref name=":8" /> and southern Canada (Alberta & Saskatchewan),<ref>{{Cite journal |last=Harington |first=C. R. |date=1973 |title=A Short-Faced Bear From Ice Age Deposits at Lebret, Saskatchewan |url=https://bluejayjournal.ca/index.php/bluejay/article/view/4039 |journal=Blue Jay |language=en |volume=31 |issue=1 |doi=10.29173/bluejay4039 |issn=2562-5667 |s2cid=222373512 |doi-access=free}}</ref><ref>{{Cite journal |last=Harington |first=C. |date=1990 |title=Vertebrates of the Last Interglaciation in Canada: A Review, with New Data |url=https://www.erudit.org/fr/revues/gpq/1997-v51-n2-gpq1935/032837ar/ |journal=Géographie physique et Quaternaire |language=en |volume=44 |issue=3 |pages=375–387 |doi=10.7202/032837ar |issn=0705-7199 |doi-access=free}}</ref><ref name=":622">{{Cite journal |last1=Burns |first1=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 |bibcode=1994CaJES..31..393B |doi=10.1139/e94-036 |issn=0008-4077}}</ref> which when unglaciated, would have formed a tundra ecosystem with an ice-free corridor to Beringia.<ref>{{Cite journal |last1=Young |first1=Robert R. |last2=Burns |first2=James A. |last3=Smith |first3=Derald G. |last4=Arnold |first4=L. David |last5=Rains |first5=R. Bruce |date=1994-08-01 |title=A single, late Wisconsin, Laurentide glaciation, Edmonton area and southwestern Alberta 2.3.CO;2 |journal=Geology |volume=22 |issue=8 |pages=683–686 |doi=10.1130/0091-7613(1994)022<0683:ASLWLG>2.3.CO;2 |issn=0091-7613}}</ref>

In the lowlands of the eastern Interior plains, the plains transitioned to closed habitat. At the terminal Pleistocene [[Sheriden Cave]], Ohio, a mosaic habitat consisting of marsh, open woodland, and patchy grassland was home to ''Arctodus simus'', ''[[Cervalces scotti]]'', caribou, peccaries ([[Platygonus compressus|''Platygonus'']], [[Long-nosed peccary|''Mylohyus'']]), [[Castoroides|giant beaver]], [[North American porcupine|porcupine]], and [[American marten|American pine marten]].<ref name=":282">{{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|volume=12 |issue=6 |pages=713–724|doi=10.1002/(SICI)1520-6548(199709)12:6<713::AID-GEA9>3.0.CO;2-1 }}</ref><ref name=":322">{{Cite journal |last1=Redmond |first1=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 |jstor=40035311 |s2cid=162034505 |issn=0002-7316}}</ref> Similar remains have been found in Indiana,<ref name=":39" /> and Kentucky.<ref>{{Cite book |last=Wilson |first=Ronald C. |date=1985 |editor=Percy H. Dougherty |title=Caves and Karst of Kentucky |url=https://kgs.uky.edu/kgsweb/olops/pub/kgs/KGS11SP12reduce.pdf |publisher=Kentucky Geological Survey, University of Kentucky Lexington |chapter=Vertebrate Remains in Kentucky Caves |volume=12 |series=Series XI |page=171 |issn=0075-5613}}</ref><ref>{{Cite journal |last=Colburn |first=Mona L. |date=July 2005 |title=Paleontological Inventory Project: Vertebrate Remains Found in Select Passages and Caves at Mammoth Cave National Park, Kentucky |url=http://npshistory.com/publications/maca/vertebrate-remains.pdf |journal=Illinois State Museum |pages=271, 281, 292}}</ref>

==== Interior Highlands ====
To the south, the [[Interior Highlands]] had a very high density of ''Arctodus simus'' specimens (second only to the black bear),<ref name=":92" /><ref name=":142" /> due to the high rate of preservation in the cave-rich region. Sympatry between the two species is most apparent in Missouri- ''Arctodus simus'' has been found in association with black bears at Riverbluff, Bat and Big Bear caves.<ref>{{Cite journal |last=Hawksley |first=Oscar |date=July 1965 |title=Short-Faced Bear (Arctodus) Fossils from Ozark Caves |url=https://caves.org/pub/journal/NSS%20Bulletin/vol%2027%20part%203.pdf |journal=Bulletin of the National Speleological Society |volume=27 |issue=3 |pages=77–92}}</ref> Big Bear Cave preserves fossilized hair associated with ''Arctodus''.<ref name=":2" /> During the Last Glacial Maximum, both bears were joined by dire wolves, coyotes, jaguars, [[snowshoe hare]], [[groundhog]]s and [[beaver]]s at Bat Cave, which also records thousands of ''Platygonus'' remains. These fauna inhabited well-watered forest-grassland [[ecotone]] with a strong taiga influence, although the region did occasionally cycle through drier, grassier periods. These open woodlands were dominated by [[pine]]s and [[spruce]], and to a lesser extent by [[oak]]s''.''<ref>{{Cite journal |last=Woodruff |first=Aaron L. |date=2016 |title=Description, Taphonomy, and Paleoecology of the Late Pleistocene Peccaries (Artiodactyla: Tayassuidae) from Bat Cave, Pulaski County, Missouri |url=https://dc.etsu.edu/cgi/viewcontent.cgi?article=4444&context=etd |journal=Department of Geosciences, East Tennessee State University |issue=Paper 3051 |via=East Tennessee State University Digital Commons @ East Tennessee State University}}</ref><ref>{{Cite journal |last1=Woodruff |first1=Aaron L. |last2=Schubert |first2=Blaine W. |date=2019-07-04 |title=Seasonal denning behavior and population dynamics of the late Pleistocene peccary Platygonus compressus (Artiodactyla: Tayassuidae) from Bat Cave, Missouri  |journal=PeerJ |volume=7 |pages=e7161 |doi=10.7717/peerj.7161 |issn=2167-8359 |pmc=6612422 |pmid=31308997 |doi-access=free }}</ref><ref>{{Cite journal |last1=Hawksley |first1=Oscar |last2=Reynolds |first2=Jack F. |last3=Foley |first3=Robert F. |date=July 1973 |title=Pleistocene Vertebrate Fauna of Bat Cave, Pulaski County, Missouri |url=https://caves.org/pub/journal/NSS%20Bulletin/Vol%2035%20num%203.pdf |journal=Bulletin of the National Speleological Society |volume=35 |issue=3 |pages=61–87}}</ref><ref>{{Cite journal |last1=Santucci |first1=Vincent L. |last2=Kenworthy |first2=Jason |last3=Kerbo |first3=Ron |date=2022-01-18 |title=An inventory of paleontological resources associated with national park service caves |url=https://digitalcommons.usf.edu/kip_articles/271 |journal=KIP Articles}}</ref><ref>{{Cite web |last1=Smith |first1=Matthew D |last2=Dorale |first2=Jeffrey A |last3=Johnson |first3=Aaron W |last4=Forir |first4=Matthew D |date=2013 |title=A speleothem record of paleoenvironmental change from Riverbluff Cave, Missouri, U.S.A |url=https://iro.uiowa.edu/esploro/outputs/abstract/A-speleothem-record-of-paleoenvironmental-change/9984240795902771 |access-date=2022-07-26 |website=iro.uiowa.edu}}</ref>

==== Eastern USA ====
[[File:Lake Rousseau.JPG|thumb|222x222px|[[Lake Rousseau]], Florida, is the south-easternmost locality which ''Arctodus simus'' is known to have inhabited.|left]]
Compared to other regions, ''Arctodus simus'' was relatively rare in eastern North America.<ref name=":02" /><ref name=":92" /><ref name=":142" /> To the north, the [[Appalachian Highlands]] were dominated by taiga.<ref name=":472" /> Post-LGM [[Saltville (archaeological site)|Saltville]], Virginia, was a mosaic of grassy/herb laden open areas intermixed with open canopy [[Taiga|boreal woodlands]] (oaks, pines, spruce, birch, firs) and marshes. Inhabiting in this [[C3 carbon fixation|C<sub>3</sub> resource]] dominated environment were ''Arctodus simus'', [[mastodon]], (southernmost) [[woolly mammoth]]s, ''Bootherium,'' horses, caribou, ''[[Megalonyx]]'', [[dire wolf|dire wolves]], beavers, ''[[Cervalces]]'', and a variety of warm-adapted reptiles, suggesting that a more mesic and less seasonal climate. Heavy bone damage on a mammoth carcass by both dire wolves and ''Arctodus'' suggests a potentially competitive scavenging relationship <ref>{{Cite thesis |degree=Master |last=Simpson |first=Emily |date=2019-05-01 |title=Paleoecology and Land-Use of Quaternary Megafauna from Saltville, Virginia |url=https://dc.etsu.edu/etd/3590 |publisher=East Tennessee State University}}</ref><ref name=":332">{{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 |bibcode=2009Borea..38..482S |s2cid=129612660}}</ref> Additional remains have been found in Virginia,<ref name=":12" /> and [[Frankstown Township, Blair County, Pennsylvania|Pennsylvania]].<ref name=":8" /><ref name=":29" />

To the south, the [[Atlantic Plain]]s covered a great expanse of lowland, from the open deciduous woodlands of the [[Atlantic coastal plain|Atlantic coast]], to the semi-arid woodland/scrub of Florida, to the spruce-fir conifer forests and open habitat of the [[Gulf Coastal Plain]]. Although scarce, this contrast of habitats highlights the adaptability of ''Arctodus simus''. At the [[Rainbow River]] and [[Lake Rousseau]] localities in Rancholabrean Florida, three ''Arctodus simus'' specimens have been recovered, alongside ''[[Smilodon]]'', [[dire wolf|dire wolves]], jaguars, ground sloths (''[[Megalonyx]]'', ''Paramylodon''), llamas (''Hemiauchenia'', ''[[Palaeolama]]''), [[Tapirus veroensis|Vero's tapir]], giant beaver, [[Neochoerus pinckneyi|capybara]], ''Holmesina'', horses, ''Bison antiquus'', [[mastodon]], [[Columbian mammoth]]s and ''Tremarctos floridanus'', in a climate similar to today's. Furthermore, the abundance of black bears, and particularly ''Tremarctos floridanus'' in Florida, has led to a theorized niche partitioning of ursids in Florida, with ''Tremarctos floridanus'' being herbivorous, and black bears and ''Arctodus simus'' being omnivorous, with ''Arctodus'' being possibly more inclined towards carnivory.<ref name=":02" /> Additional finds of south-eastern ''Arctodus simus'' are from Alabama,<ref>{{Cite journal |last1=Ebersole |first1=Jun A. |last2=Ebersole |first2=Sandy M. |date=December 2011 |title=Late Pleistocene Mammals of Alabama: A Comprehensive Faunal Review with 21 Previously Unreported Taxa |url=http://almnh.museums.ua.edu/wp-content/uploads/sites/2/2018/12/BALMNH_No_28_2011.pdf |journal=Alabama Museum of Natural History Bulletin |volume=28 |pages=24–25 |via=University of Alabama}}</ref> Arkansas,<ref>{{Cite journal |last1=Baghai-Riding |first1=Nina L. |last2=Husley |first2=Danielle B. |last3=Beck |first3=Christine |last4=Blackwell |first4=Eric |date=December 2017 |title=Late Pleistocene Megafauna from Mississippi Alluvium Plain Gravel Bars |url=https://paludicolavertpaleo.files.wordpress.com/2019/11/11-3-baghai-riding-2017.pdf |journal=Paludicola |volume=11 |issue=3 |pages=124–147 |via=Rochester Institute of Vertebrate Paleontology}}</ref> Mississippi,<ref>{{Cite journal |last=Ruddell |first=Michael W. |date=December 1999 |title=Quaternary Vertebrate Paleoecology of the Central Mississippi Alluvial Valley; Implications for the Initial Human Occupation |url=https://trace.tennessee.edu/cgi/viewcontent.cgi?article=3184&context=utk_graddiss |journal=Tennessee Research and Creative Exchange |via=University of Tennessee, Knoxville}}</ref><ref>{{Cite journal |last1=Kurtén |first1=Björn |last2=Kaye |first2=John M. |date=March 1982 |title=Late Quaternary Carnivora from the Black Belt, Mississippi |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3885.1982.tb00519.x |journal=Boreas |language=en |volume=11 |issue=1 |pages=47–52 |doi=10.1111/j.1502-3885.1982.tb00519.x|bibcode=1982Borea..11...47K }}</ref><ref>{{Cite journal |last=Kaye |first=John Morgan |date=1974 |title=Pleistocene Sediment and V ocene Sediment and Vertebrate Fossil Associations in the ossil Associations in the Mississippi Black Belt: a Genetic Approach |url=https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=3611&context=gradschool_disstheses |journal=LSU Historical Dissertations and Theses. |volume=2612 |via=Louisiana State University}}</ref> South Carolina,<ref>{{Cite web |last=Miller |first=Andrew |title=SC diver finds rare prehistoric bear tooth fossil in Cooper River |url=https://www.postandcourier.com/news/sc-diver-finds-rare-prehistoric-bear-tooth-fossil-in-cooper-river/article_c8cf9104-8d7a-11eb-bd4d-af15386d585a.html |access-date=2022-07-09 |website=Post and Courier |date=26 March 2021 |language=en}}</ref> and Texas.<ref name=":13" /><ref>{{Cite journal |last=Slaughter |first=Bob H. |date=1966 |title=The Moore Pit Local Fauna; Pleistocene of Texas |journal=Journal of Paleontology |volume=40 |issue=1 |pages=78–91 |jstor=1301775 |issn=0022-3360}}</ref>

==== Beringia ====
[[File:Wolf_with_Caribou_Hindquarter.jpg|thumb|230x230px|''Arctodus'' is suggested to have had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|Beringian wolves]], akin to modern [[Wolf|wolves]] and [[brown bear]]s.]]
Mostly isolated by the Cordilleran and Laurentide ice sheets, [[Beringia]] is considered ecologically separate to the rest of North America, being largely an extension of the Eurasian [[mammoth steppe]].<ref>{{Citation |last1=David Webb |first1=S. |title=Vertebrate paleontology |date=2003 |url=https://linkinghub.elsevier.com/retrieve/pii/S157108660301025X |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.|series=Developments in Quaternary Sciences }}</ref> However, the occasional opening of an ice-free corridor, and the migration barrier of the Beringian gap, meant that Eastern Beringia ([[Alaska]] and the [[Yukon]]) supported a unique assemblage of fauna, with many endemic North American fauna flourishing.<ref name=":57">{{Cite journal |last1=Churcher |first1=C. S. |last2=Morgan |first2=A. V. |last3=Carter |first3=L. D. |date=2011-02-08 |title=Arctodus simus from the Alaskan Arctic Slope |url=https://cdnsciencepub.com/doi/10.1139/e93-084 |journal=Canadian Journal of Earth Sciences |volume=30 |issue=5 |pages=1007–1013 |language=en |doi=10.1139/e93-084}}</ref> This mostly open and treeless steppe-tundra, dominated by grasses, sedges, ''Artemisia spp.'', and a range of other forbs had a cold, dry climate, which prevented glaciation. Currently, all specimens of ''A. simus'' in Beringia have been dated to a 27,000 year window (50,000 BP - 23,000 BP) from Eastern Beringia,<ref name=":19" /><ref name=":156" /><ref name=":8" /><ref name=":56">{{Cite book |last=Stark |first=Mike |url=https://www.jstor.org/stable/j.ctv2br108d |title=Chasing the Ghost Bear: On the Trail of America's Lost Super Beast |date=2022 |publisher=University of Nebraska Press |isbn=978-1-4962-2902-1}}</ref> while additional undated remains may be of [[Sangamonian]] age.<ref>{{Cite journal |last=Harington |first=C. R. |date=1980 |title=Radiocarbon Dates on Some Quaternary Mammals and Artifacts from Northern North America |journal=Arctic |volume=33 |issue=4 |pages=815–832 |doi=10.14430/arctic2598 |jstor=40509084 |issn=0004-0843|doi-access=free }}</ref><ref name=":36" /> Unlike contemporary Beringian carnivorans, ''A. simus'' apparently never inhabited western Beringia (and therefore Asia).<ref name=":36" /> The largest known skull of ''A. simus'' was recovered from the Yukon, and may represent the largest specimen known.<ref name=":110" /><ref>{{Cite web |title=The Ottawa naturalist: Vol. 25, no. 2 (May 1911) - Canadiana |url=https://www.canadiana.ca/view/oocihm.8_04906_273/9 |access-date=2023-01-10 |website=www.canadiana.ca}}</ref>

The [[Alaska North Slope|North Slope]] of Alaska <40,000 BP (Ikpikpuk and Titaluk rivers) preserves an upland and floodplain environment, with horses, bison then caribou being the most populous herbivores, and woolly mammoths, [[muskox]], elk and [[saiga antelope]] more scarce. [[Panthera spelaea|Cave lions]], bears (''Ursus arctos'' and ''Arctodus simus''), and [[Beringian wolf|Beringian wolves]] made up the megafaunal predator guild.<ref name="sciencedirect.com">{{Cite journal |last1=Mann |first1=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 |bibcode=2013QSRv...70...91M |issn=0277-3791}}</ref><ref>{{Cite journal |last1=Monteath |first1=Alistair J. |last2=Gaglioti |first2=Benjamin V. |last3=Edwards |first3=Mary E. |last4=Froese |first4=Duane |date=2021-12-28 |title=Late Pleistocene shrub expansion preceded megafauna turnover and extinctions in eastern Beringia |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=52 |pages=e2107977118 |doi=10.1073/pnas.2107977118 |issn=0027-8424 |pmc=8719869 |pmid=34930836|bibcode=2021PNAS..11807977M |doi-access=free }}</ref>  Isotope data implies that caribou and muskox were principal components of the carnivorous portion of ''Arctodus simus''<nowiki/>' Arctic diet, suggesting that the warmer, wetter vegetation on the margins of the dry mammoth steppe (similar to the moist acidic [[tundra]] vegetation which [[Tundra of North America|dominates today]]) was the preferred habitat of ''Arctodus'' in Beringia.<ref name=":312" /><ref name="sciencedirect.com" />

Additionally, upon the flooding of the [[Bering Strait]] and [[Paludification|expansion]] of moist tundra and [[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 wolves and ''Arctodus'' persisted. Simultaneously, most megafaunal herbivores in Beringia experienced population bottlenecks, whilst [[Woolly mammoth|mammoth]] populations steadily declined. This restriction of prey and habitat could explain the extinctions. However, genetically distinct cave lions and brown bears appear in [[MIS 2|MIS-2]] circa the extinction of ''Arctodus'' in a re-emerged Beringia ~23,000 BP, opening up the possibility that some level of competition was at play.<ref name=":19" /><ref name=":312" /><ref name=":422">{{Cite journal |last1=Murchie |first1=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 |journal=Nature Communications |language=en |volume=12 |issue=1 |page=7120 |bibcode=2021NatCo..12.7120M |doi=10.1038/s41467-021-27439-6 |issn=2041-1723 |pmc=8654998 |pmid=34880234}}</ref><ref name=":432">{{Cite journal |last1=Barnes |first1=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 |bibcode=2002Sci...295.2267B |doi=10.1126/science.1067814 |issn=0036-8075 |pmid=11910112 |s2cid=5883943}}</ref><ref>{{Cite journal |last1=Leonard |first1=Jennifer A. |last2=Vilà |first2=Carles |last3=Fox-Dobbs |first3=Kena |last4=Koch |first4=Paul L. |last5=Wayne |first5=Robert K. |last6=Van Valkenburgh |first6=Blaire |date=July 2007 |title=Megafaunal Extinctions and the Disappearance of a Specialized Wolf Ecomorph |journal=Current Biology |volume=17 |issue=13 |pages=1146–1150 |doi=10.1016/j.cub.2007.05.072 |pmid=17583509 |issn=0960-9822|doi-access=free |hdl=10261/61282 |hdl-access=free }}</ref> The idea that ''Arctodus'' had a [[Kleptoparasitism|kleptoparasitic]] relationship with [[Beringian wolf|wolves]] and ''[[Homotherium]]'' in Beringia has been explored,<ref name=":312" /> with the additional possibility that ''Arctodus'' successfully competed against brown bears and ''Homotherium'' for access to [[Reindeer|caribou]] pre-[[Last Glacial Maximum|LGM]].<ref name=":412">{{Cite journal |last1=Fox-Dobbs |first1=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 |bibcode=2008PPP...261...30F |issn=0031-0182}}</ref>

The local extinction of ''Arctodus'' in Beringia ~23,000 BP (possibly due to sharp climatic cooling associated with [[Heinrich event|Heinrich Event-2]]),<ref name=":19" /><ref name=":156" /> was much earlier than in other parts of its range. While recolonized by [[Panthera spelaea|cave lions]] and [[brown bear]]s from Eurasia, ''Arctodus'' did not repopulate Beringia once the ice-free corridor to the south re-opened later in the Pleistocene.<ref name=":19" /><ref name=":182">{{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 |url=http://eprints.gla.ac.uk/138297/1/138297.pdf |journal=Nature |volume=537 |issue=7618 |pages=45–49 |bibcode=2016Natur.537...45P |doi=10.1038/nature19085 |pmid=27509852 |s2cid=4450936}}</ref>

== Map of fossil localities ==
{{location map+|North America|relief=yes|width=600|float=center|caption=Interactive distribution map of ''Arctodus'' {{small|(hover over dots for locality information)}}<br /> 
Legend: [[File:Cyan pog.svg|8px]] ''A. pristinus'' ([[Blancan|Late Blancan]] / [[Irvingtonian]])

[[File:Blue pog.svg|8px]] Early/Middle Pleistocene (Irvingtonian) ''A.simus''

[[File:Red pog.svg|8px]] Late Pleistocene ([[Rancholabrean]]) ''A. simus''

[[File:Purple 8000ff pog.svg|8px]] Radiocarbon dated ''A.simus'' (14C Date (1σ), ≤50,000 BP)|places={{location map~ |North America| label = American Falls (Hop-Strawn Pit, Cedar Ridge, 26,500 ± 3500 BP)| position = none | lat= 42.8 | long= -112.9 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Birch Creek (34,974 ± 652 BP) | position = none | lat= 66.255187 | long= -145.835918 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Bonner Springs (Kansas River, 10,921 ± 50 BP) | position = none | lat=39.059722 | long=-94.883611 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Chiquihuite Cave (11,419 ± 34 BP) | position = none | lat= 24.609470 | long= -101.188001 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Cueva Quebrada (12,280 ± 170) | position = none | lat= 29.711764 | long= -101.387611 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Fairbanks (Cleary, Cleary Creek, Dawson Cut, Engineer Creek, Ester, Ester Creek, Eva Creek Mine, Gold Hill, Goldstream, No.2 G-Strip Area, Upper Cleary River Beds, 39,565 ± 1126 BP - 20,524 ± 180 BP?) | position = none | lat= 64.846267 | long= -147.734202 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Friesenhahn Cave (10,814 ± 55 BP) | position = none | lat=29.682853 | long=-98.477758 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Fulton County (11,040 ± 310 BP) | position = none | lat=41.0619441 |long=-86.206667|mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Gold Run Creek (26,040 ± 270 BP) | position = none | lat=63.698261 |long=-138.609632 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Huntington Dam (10,976 ± 40 BP) | position = none | lat=39.596595 |long=-111.273836 |mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Ikpikpuk River (27,160 ± 280 BP) | position = none | lat=69.683333 |long= -154.900000 |mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Island Ford Cave (34,080 ± 480 BP) | position = none | lat=37.786111 | long=-79.988889| mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = La Brea Tar Pits (35,370 - 26,427 cal. BP (≤50,000?)) | position = none | lat=34.0628 |long=-118.356|mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Meander Cave (37,500 cal. BP?) | position = none | lat= 66.729966 | long= -139.258976 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Natural Trap Cave (20,220 ± 150 BP) | position = none | lat=44.973333 | long= -108.193056 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Pellucidar Cave (11,615 ± 30 BP) | position = none | lat=50.400278 | long=-126.975833| mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Potter Creek Cave (& Samwell Cave, 12,650 ± 350 BP) | position = none | lat= 40.783624 | long= -122.279719 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Rainbow Beach (21,500 ± 700 BP)| position = none | lat= 42.881029 | long= -112.716195 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Salt Lake Valley (Silver Creek/Bonneville, 12,650 ± 70 BP) | position = none | lat=40.6839 | long=-111.978|mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Saltville Valley (14,853 ± 55 BP) | position = none | lat=36.873611 |long=-81.760833|mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = San Miguel Island (Daisy Cave, California Channel Islands, 14,130 ± 70 BP) | position = none | lat=34.033333 |long=-120.383333|mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Sheriden Cave (11,566 ± 40 BP) | position = none | lat=40.980733 | long=-83.444783| mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Sixtymile River (44,240 ± 930 BP) | position = none | lat= 63.554796 | long= -139.825129 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = The Mammoth Site (26,075 ± 975 BP) | position = none | lat=43.42471 | long= -103.48313 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Three-Forks Cave (Gittin' Down Mountain, 34,063 ± 460 BP) | position = none | lat=35.76509 |long=-94.74022|mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Titaluk River (42,600 ± 2,200 BP) | position = none | lat=69.427684 |long=-156.999745 |mark= Purple 8000ff pog.svg}}

{{location map~ |North America| label = Airport Lane | position = none | lat= 45.294329 | long= -118.021097 | mark= Red_pog.svg}}
{{location map~ |North America| label = Alameda Tube | position = none | lat= 37.792099 | long= -122.275258 | mark= Red_pog.svg}}
{{location map~ |North America| label = Albuquerque Gravel Pits | position = none | lat= 35.013227 | long= -106.722222 | mark= Red_pog.svg}}
{{location map~ |North America| label = Atepetzingo (Rancho de Tepetzingo) | position = none | lat= 18.685152 | long= -98.505050 | mark= Red_pog.svg}}
{{location map~ |North America| label = Beaver Crossing (unknown age) | position = none | lat= 40.774998 | long= -97.282600 | mark= Red_pog.svg}}
{{location map~ |North America| label = Beemer & West Point (Cuming County Wet Gravel Pits) | position = none | lat= 41.825600 | long= -96.716747 | mark= Red_pog.svg}}
{{location map~ |North America| label = Big Bear Cave, Bat Cave, Carroll Cave, West Cave | position = none | lat= 37.927957 | long= -92.168076 | mark= Red_pog.svg}}
{{location map~ |North America| label = Big Bear Site ("Arctodus site", Blackwater Draw) | position = none | lat= 33.466801 | long= -105.793276 | mark= Red_pog.svg}}
{{location map~ |North America| label = Bitter Springs Playa (Rogers Ridge, Fort Irwin) | position = none | lat= 35.227091 | long= -116.435312 | mark= Red_pog.svg}}
{{location map~ |North America| label = Blacktail Cave | position = none | lat= 47.106583 | long= -112.274182 | mark= Red_pog.svg}}
{{location map~ |North America| label = Box Butte Creek | position = none | lat= 42.307870 | long= -102.746110 | mark= Red_pog.svg}}
{{location map~ |North America| label = Burnet Cave (Rocky Arroyo) | position = none | lat= 32.3667 | long= -104.7833 | mark= Red_pog.svg}}
{{location map~ |North America| label = Cedar Creek (Black Belt, c.f. simus) | position = none | lat=33.341435 | long= -88.437362 | mark= Red_pog.svg}}
{{location map~ |North America| label = Cedral | position = none | lat=23.816667 |long=-100.716667|mark= Red_pog.svg}}

{{location map~ |North America| label = 'Chat' (Chatanika River) | position = none | lat= 65.106979 | long= -147.473061 | mark= Red_pog.svg}}
{{location map~ |North America| label = Chicken Creek (Lost Chicken Creek?) | position = none | lat= 64.063024 | long= -141.895792 | mark= Red_pog.svg}}

{{location map~ |North America| label = Clover Bar (Edmonton) | position = none | lat=53.596164 | long= -113.354075 | mark= Red_pog.svg}}
{{location map~ |North America| label = Conkling Cavern? | position = none | lat= 32.19 | long= -106.585278 | mark= Red_pog.svg}}
{{location map~ |North America| label = Cooper River| position = none | lat=33.078822 | long= -79.925568 | mark= Red_pog.svg}}
{{location map~ |North America| label = Copper Mine| position = none | lat=37.917864 | long=  -114.484980 | mark= Red_pog.svg}}
{{location map~ |North America| label = Cripple Creek | position = none | lat= 62.766667 | long= -137.383333 | mark= Red_pog.svg}}
{{location map~ |North America| label = Dalhart | position = none | lat= 35.886840 | long= -102.653832 | mark= Red_pog.svg}}
{{location map~ |North America| label = Diamond Valley | position = none | lat= 33.678333 | long= -117.041667 | mark= Red_pog.svg}}
{{location map~ |North America| label = Drews Gap (footprints, Lakeview) | position = none | lat= 42.19927 | long= -120.615498 | mark= Red_pog.svg}}
{{location map~ |North America| label = Duck Flat | position = none | lat= 41.016508 | long= -119.884385 | mark= Red_pog.svg}}
{{location map~ |North America| label = Fern Cave| position = none | lat=34.648933 | long= -86.297864 | mark= Red_pog.svg}}
{{location map~ |North America| label = Fort Qu' Appelle (Bliss Gravel Pit-Echo Lake Gravel) | position = none | lat= 50.8 | long= -103.9 | mark= Red_pog.svg}}
{{location map~ |North America| label = Fossil Lake | position = none | lat= 43.3258 | long= -120.4909 | mark= Red_pog.svg}}
{{location map~ |North America| label = Frankstown Cave | position = none | lat= 40.450969 | long= -78.337221 | mark= Red_pog.svg}}
{{location map~ |North America| label = Gatesville (Coryell County, Ursidae c.f. A. simus) | position = none | lat= 31.414128 | long= -97.739606 | mark= Red_pog.svg}}
{{location map~ |North America| label = Glass Cave | position = none | lat= 38.247817 | long= -84.946015 | mark= Red_pog.svg}}
{{location map~ |North America| label = Hall's Cave | position = none | lat= 30.135083 | long= -99.537889 | mark= Red_pog.svg}}
{{location map~ |North America| label = Isleta Caves | position = none | lat= 34.8833 | long= -106.883 | mark= Red_pog.svg}}
{{location map~ |North America| label = Jaguar Cave | position = none | lat= 44.285370 | long= -112.906826 | mark= Red_pog.svg}}
{{location map~ |North America| label = Jinglebob | position = none | lat= 37.2 | long= -100.3 | mark= Red_pog.svg}}
{{location map~ |North America| label = Keams Canyon | position = none | lat= 35.813586 | long= -110.204220 | mark= Red_pog.svg}}
{{location map~ |North America| label = Kotzebue | position = none | lat= 66.856553 | long= -162.620977 | mark= Red_pog.svg}}
{{location map~ |North America| label = La Cinta Portalitos | position = none | lat=20.085833 |long=-101.158611|mark= Red_pog.svg}}
{{location map~ |North America| label = Labor-of-Love Cave | position = none | lat= 39.3667 | long= -114.6 | mark= Red_pog.svg}}
{{location map~ |North America| label = Lake San Agustin (White Lake)| position = none | lat= 33.924444 | long= -108.227778 | mark= Red_pog.svg}}
{{location map~ |North America| label = Lebret | position = none | lat=50.757128| long= -103.702833 | mark= Red_pog.svg}}
{{location map~ |North America| label = Lilian Creek | position = none | lat= 65.516989 | long= -148.573169 | mark= Red_pog.svg}}
{{location map~ |North America| label = Little Box Elder Cave | position = none | lat= 42.7833 | long= -105.683 | mark= Red_pog.svg}}
{{location map~ |North America| label = Lubbock Lake| position = none | lat=33.621944 | long= -101.889722 | mark= Red_pog.svg}}
{{location map~ |North America| label = Manix Lake (Camp Cady) | position = none | lat= 34.941383 | long= -116.609557 | mark= Red_pog.svg}}
{{location map~ |North America| label = Maricopa Tar Seeps | position = none | lat= 35.061276 | long= -119.392818 | mark= Red_pog.svg}}
{{location map~ |North America| label = Moore Pit (Hill Shuler/ Trinity River) | position = none | lat= 32.711180 | long= -96.706766 | mark= Red_pog.svg}}
{{location map~ |North America| label = Old Crow Flats | position = none | lat=67.441 |long=-139.82|mark= Red_pog.svg}}
{{location map~ |North America| label = Oregon Caves? | position = none | lat= 42.098277 | long= -123.407216 | mark= Red_pog.svg}}
{{location map~ |North America| label = Oso Cave | position = none | lat= 32.120244 | long= -104.581977 | mark= Red_pog.svg}}
{{location map~ |North America| label = Pendejo Cave? | position = none | lat= 32.416667 | long= -105.916667 | mark= Red_pog.svg}}
{{location map~ |North America| label = Powder Mill Creek Cave, Round Spring Cave | position = none | lat= 37.193158 | long= -91.171013 | mark= Red_pog.svg}}
{{location map~ |North America| label = Proctor Cave | position = none | lat= 37.148637 | long= -86.066441 | mark= Red_pog.svg}}
{{location map~ |North America| label = Prospects Cave | position = none | lat= 44.717259 | long= -107.291610 | mark= Red_pog.svg}}
{{location map~ |North America| label = Red Willow local fauna (Upper Republican River) | position = none | lat= 40.242093 | long= -100.332057 | mark= Red_pog.svg}}
{{location map~ |North America| label = Red Willow local fauna (McCook, unknown age) | position = none | lat= 40.200133 | long= -100.705910 | mark= Red_pog.svg}}
{{location map~ |North America| label = Riverbluff Cave | position = none | lat= 37.106298 | long= -93.32927 | mark= Red_pog.svg}}
{{location map~ |North America| label = San Juan Island | position = none | lat= 48.528064 | long= -122.979888 | mark= Red_pog.svg}}
{{location map~ |North America| label = Schultz Cave | position = none | lat= 30.212894 | long= -99.839868 | mark= Red_pog.svg}}
{{location map~ |North America| label = Seale Pit (Hill-Shuler/Trinity River) | position = none | lat= 32.773207 | long= -97.010381 | mark= Red_pog.svg}}
{{location map~ |North America| label = Selawik | position = none | lat= 66.583862 | long= -159.981115 | mark= Red_pog.svg}}
{{location map~ |North America| label = Skeleton Cave | position = none | lat= 43.950267 | long= -121.1773 | mark= Red_pog.svg}}
{{location map~ |North America| label = Spalding Site | position = none | lat= 46.450558 | long= -116.818228 | mark= Red_pog.svg}}
{{location map~ |North America| label = Tequixquiac | position = none | lat= 19.898093 | long= -99.161302 | mark= Red_pog.svg}}
{{location map~ |North America| label = The Bar (Central Mississippi Alluvial Valley) | position = none | lat=33.712994 | long= -91.183510 | mark= Red_pog.svg}}
{{location map~ |North America| label = Troublesome Creek | position = none | lat= 41.419528 | long= -95.018005 | mark= Red_pog.svg}}
{{location map~ |North America| label = Tofty (Tofty Placer District)| position = none | lat= 65.084415 | long= -150.895315 | mark= Red_pog.svg}}
{{location map~ |North America| label = U-Bar Cave | position = none | lat= 31.5667 | long= -108.4 | mark= Red_pog.svg}}
{{location map~ |North America| label = Valsequillo | position = none | lat= 18.925262 | long= -98.146481 | mark= Red_pog.svg}}
{{location map~ |North America| label = Wasden Site (Owl Cave) | position = none | lat= 43.443773 | long= -112.217553 | mark= Red_pog.svg}}
{{location map~ |North America| label = Wright Materials North | position = none | lat= 27.952547 | long= -97.776587 | mark= Red_pog.svg}}
{{location map~ |North America| label = Zacoalco | position = none | lat=20.233333 |long=-103.583333|mark= Red_pog.svg}}

{{location map~ |North America| label = Arkalon | position = none | lat=37.143012 | long= -100.807423 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Cass County | position = none | lat= 41.057782 | long= -96.046120 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Doeden Gravel Pit (Yellowstone River) | position = none | lat= 46.4 | long= -105.8 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Fairmead Landfill| position = none | lat=37.061631 | long= -120.194195 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Gordon| position = none | lat=42.798152 | long= -102.180767 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Hay Springs| position = none | lat=42.7 | long= -102.5 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Irvington| position = none | lat=37.527222 | long= -121.946111 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Murrieta (Riverside)| position = none | lat=33.570661 | long= -117.200222 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Rock Creek| position = none | lat=34.54173 | long= -101.42989| mark= Blue_pog.svg}}
{{location map~ |North America| label = Rushville | position = none | lat=42.705436 | long= -102.481423| mark= Blue_pog.svg}}
{{location map~ |North America| label = Vallecito Creek (Anza-Borrego) | position = none | lat=33.024534 | long= -116.209792 | mark= Blue_pog.svg}}
{{location map~ |North America| label = Victorville (cf. simus) | position = none | lat=34.667995 | long= -117.328125 | mark= Blue_pog.svg}}

{{location map~ |North America| label = 111 Ranch (Arctodus sp.) | position = none | lat= 32.718633 | long= -109.475097 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Aguascalientes (Cedazo) | position = none | lat=21.976449 | long= -102.283105 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Apollo Beach, Leisey Shell Pit 1, Leisey Shell Pit 1A & Leisey Shell Pit 3 | position = none | lat=27.690000 | long= -82.500000 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Bass Point Waterway, Rigby Shell Pit, Venice Beach | position = none | lat=27.099834 | long= -82.460045 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Coleman 2A | position = none | lat=28.760000 | long= -82.050000 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Crystal River Power Plant (Inglis 1A & Inglis 1B) | position = none | lat=29.010000 | long= -82.690000 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Cumberland Bone Cave | position = none | lat=39.691389 | long= -78.788472 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Haile 16A | position = none | lat=29.690000 | long= -82.560000 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Kissimmee 6 | position = none | lat=27.385283 | long= -81.083256 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = La Union (Mesilla Basin Fauna B) | position = none | lat= 31.943252 | long= -106.667462 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Lost World Caverns (Grapevine Cave) | position = none | lat=37.8326 | long= -80.4469 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = McLeod Limerock Mine | position = none | lat=29.474891 | long= -82.589610 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Morgan River | position = none | lat=32.448443 | long= -80.584139 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Myrtle Beach | position = none | lat=33.752468 | long=  -78.799589 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Port Charlotte | position = none | lat=26.990278 | long= -82.105833 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Port Kennedy Cave | position = none | lat=40.10182 | long= -75.42462 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Santa Fe River 1 | position = none | lat=29.840000 | long= -82.700000 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Sebastian Canal 2 | position = none | lat=27.889646 | long= -80.734793 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Stout's Ranch (Saw Rock Canyon) | position = none | lat= 37.1 | long= -100.9 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Whitlock Oil Well (San Simon Creek, Arctodus sp.) | position = none | lat= 32.552721 | long= -109.335934 | mark= Cyan_pog.svg}}

{{location map~ |North America| label = Ashley River (Bee's Ferry, "Wando Formation"), Cooper River, Ladson Formation, Walrus Ditch Local Fauna  | position = none | lat=32.847008 | long= -80.050759 | mark= Cyan_pog.svg}}
{{location map~ |North America| label = Lake Rousseau & Rainbow River| position = none | lat=29.033333 | long= -82.508333 | mark= Red_pog.svg}}
{{location map~ |North America| label = McKittrick Tar Seeps (11,040 ± 310 BP) | position = none | lat=35.296314 |long=-119.626014 |mark= Purple 8000ff pog.svg}}

{{location map~ |North America| label = Perkins Cave (16,910 ± 50 BP) | position = none | lat=38.008889 |long=-92.746389 |mark= Purple 8000ff pog.svg}}

{{location map~ |North America| label = Cowichan Head (22,750 ± 140 BP) | position = none | lat= 48.555260 | long= -123.363879 | mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = La Sena (19,487 ± 95 BP) | position = none | lat=40.53325 |long=-100.384545| mark= Purple 8000ff pog.svg}}
{{location map~ |North America| label = Dawson (Canyon Creek, Dawson City, Eldorado Creek, Hester Creek, Lower Hunker Creek, Ophir Creek, Quartz Creek, 49,800 cal. BP - 22,417 ± 452 BP) | position = none | lat=63.97 |long=-139.1 |mark= DeepPink pog.svg}}

{{location map~ |North America| label = White Sands National Park (footprint, ~18,500 BP) | position = none | lat=32.770514 | long= -106.401820 | mark= Purple 8000ff pog.svg}}}}

== Relationships with other bears ==

=== ''Arctodus pristinus'' ===
In the Early Pleistocene, ''Arctodus pristinus'' was much more populous the south-east of North America, whereas the [[American black bear|black bear]] was more common in the north-east.<ref>{{Cite book |last1=Lucas |first1=Spencer G. |url=https://books.google.com/books?id=ZFfPDwAAQBAJ&dq=Cumberland+Bone+Cave+arctodus&pg=PA740 |title=Fossil Record 6 Volume 2 |last2=Sullivan |first2=Robert M. |publisher=New Mexico Museum of Natural History and Science |language=en}}</ref> The black bear has inhabited North America since at least the [[Mid-Pleistocene Transition|Middle Pleistocene]],<ref name=":14" /> while ''[[Tremarctos floridanus]]'', a tremarctine bear inhabiting western North America at the time, is very similar to ''A. pristinus'' in terms of size, skeletal anatomy, and dietary preferences.<ref name=":5" />

Despite this, generally speaking large tremarctine fossils from the Early and Middle Pleistocene of Florida are considered to be ''A. pristinus'', whereas those from the Late Pleistocene of Florida are considered to be ''T. floridanus''. Indeed, black bears and ''Tremarctos floridanus'' are believed to have only colonized Florida with the extinction of ''A. pristinus'' (both of which only appear in Florida in the [[Late Pleistocene]]), however, ''T. floridanus'' could yet still be found from older sites in Florida.<ref name=":5" /> ''T. floridanus'' was possibly being an ecological replacement of ''A. pristinus'', with ''T. floridanus'' finds being widespread in Rancholabrean Florida and the wider southeastern United States.<ref name=":5" /><ref name=":10" /><ref name=":92" />

The evolution of ''Arctodus simus'', competition with ''[[Tremarctos floridanus]]'' and [[American black bear|black bears]], 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=":02" /><ref name=":92" /> There are dubious records of ''A. pristinus'' in South Carolina and California from the [[Sangamonian|Late Pleistocene]],<ref name=":822" /><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 |bibcode=2007Radcb..49..117F |doi=10.1017/S0033822200041941 |s2cid=130708736 |doi-access=free}}</ref> however these are heavily disputed,<ref name=":45" /><ref name=":47" /> with modern research establishing ''A. pristinus'' existing between the Pliocene-Pleistocene boundary and the Middle Pleistocene.<ref name=":5" /><ref name=":02" /><ref name=":45" />

=== ''Arctodus simus'' ===
[[File:Arctodus Simus, Hot Springs, South Dakota.jpg|thumb|''Arctodus simus'' reconstruction at the [[The Mammoth Site|Hot Springs Mammoth Site]], South Dakota.]]
The most commonly accepted ecological parallel of ''Arctodus simus'' in scientific literature is the brown bear.<ref name="Figueiridio_et_al_20102" /><ref name=":302" /><ref name=":156" /> Both brown bears and ''Arctodus simus'' exhibit a high degree of dietary variability, and while [[Dietary biology of the brown bear|largely herbivorous]], meat can be an important dietary element to certain populations of both species.<ref name=":312" /> Additionally, the potential of habitual kleptoparasitism is often noted in ''Arctodus'', with brown bears being opportunistic, curious, and regularly stealing kills from smaller predators.<ref name=":272" /><ref name=":312" /> One past theory behind the extinction of ''Arctodus simus'' is that ''A. simus'' may have been out-competed by brown bears as the latter expanded southwards from eastern Beringia ~13,000 BP, and gradually established itself in North America.<ref name=":362" />

However this has been refuted as new dates establish an extended coexistence, with some isolated ''A. simus'' remains being re-evaluated as brown bears.<ref name=":19" /><ref name=":156" /> Brown bears (along with [[American lion|lions]], [[bison]] and [[red fox]]es) first emigrated to North America via [[Beringia]] during the [[Illinoian (stage)|Illinoian Glaciation]], with brown bears first arriving between ~177,000 BP and ~111,000 BP in East Beringia.<ref name=":19" /> Genetic divergences suggest brown bears first migrated south during [[Marine Isotope Stage 5|MIS-5]] (~92,000 - 83,000 BP) upon the opening of the ice-free corridor,<ref name=":19" /><ref name=":14" /> with the first fossils being near Edmonton (26,000 BP).<ref name=":156" /> On a continent-wide scale, although the brown bear and ''Arctodus simus'' were [[Sympatry|sympatric]] at times as brown bears spread through North America, ''Arctodus simus'' may typically have dominated competitive interactions, and displaced brown bears from specific localities.<ref name=":156" /> Additionally, ''Arctodus''<nowiki/>' prolonged co-existence with black bears may have put significant constraints on the black bear's evolution.<ref name="evolution" />

At the end of the Pleistocene, one reason brown bears 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 habitat.<ref name=":156" /> Brown bears and ''Arctodus'' have been discovered together in Alaska (then Beringia) between 50,000 BP and 34,000 BP,<ref name=":19" /> and in later Pleistocene deposits in [[Vancouver Island]], [[Maricopa, California|California]], Wyoming and Nevada.<ref name=":8" /><ref name=":156" />

==== ''<small>Beringia</small>'' ====
Isotope values (''[[Δ13C|δ]]''<sup>[[Δ13C|13]]</sup>[[Δ13C|C]] and [[Δ15N|''δ''<sup>15</sup>N]]) in numerous [[Beringia]]n ''Arctodus simus'' specimens suggests ''A. simus'' usually occupied a higher [[trophic level]] compared with invading brown bears. While some Beringian brown bears consumed salmon as well as vegetation, reduced signatures of terrestrial meat consumption were mostly noted. On the other hand, data from Beringian specimens of ''Arctodus'' clustered much more tightly, and suggested that only terrestrial sources of meat were important for Beringian ''Arctodus''.<ref name=":402" /> The forcing of a smaller bear into a more herbivorous diet has been compared to the modern relationship between brown bears and American black bears.<ref name=":272" /><ref name=":312" /> Where they overlap, black bears take the lower trophic niche, with lower population densities, much smaller territorial ranges, and seasonal migrations.<ref name=":14" /> That ''Arctodus simus'' (along with local climate change) 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=":422" /><ref name=":432" /> When ''Arctodus'' went extinct in Beringia ~23,000 BP, brown bears recolonized [[Beringia]], but had more carnivorous diets than their Beringian kin pre ~34,000 BP. This bolsters the idea that these bears competed for similar resources and niches.<ref name=":19" /><ref name=":156" /> Extinction and repopulation is further evidenced by the high genetic (mitochondrial) diversity of Beringian brown bears in contrast with Beringian ''Arctodus simus''. This contrast in genetic diversity has also been hypothesized to suggest that while female brown bears have a [[Philopatry|permanent home range]], female ''Arctodus simus'' may not have (at least not to the same extent).<ref name=":49" /><ref name=":19" />[[File:Brown bear (Ursus arctos arctos) running.jpg|thumb|The brown bear was a direct competitor of ''Arctodus simus''.]]

==== ''<small>Vancouver Island</small>'' ====
Brown bears, black bears and ''Arctodus simus'' all co-existed on Vancouver Island once the island de-glaciated ~14,500 BP.<ref name=":14" /><ref name=":156" /> According to an isotope analysis, all three bears relied on terrestrial resources, with black bears occupied a distinctly lower trophic position in relation to the brown bear, with ''Arctodus'' holding an intermediate position. This may be an underestimate, as the ''Arctodus'' specimens from Vancouver Island are believed to be female; as per brown & black bears, female ''A. simus'' may have had a significant decrease in protein consumption compared with male ''A. simus'' when co-existing with brown bears. Additionally, an analysis of ''Arctodus''<nowiki/>' data suggested that when consuming protein, [[Threonine|meat was preferred]].<ref name=":14" /> It is possible that the each species was [[Niche partition|specialized to different environmental settings]], which vary greatly across small geographical areas on the mountainous island, although both ''Arctodus simus'' and brown bears appeared to have preferred more open habitats.<ref name=":14" />

=== <small>Convergent evolution</small> ===
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 {{Convert|1200|kg|lb}} and {{Convert|412|kg|lb}},<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 |doi-access=free}}</ref><ref name="Figueiridio_et_al_20102" /> with the largest specimens of either species being said to be comparable to one another.<ref name=":32" /><ref name=":302" /> The panda-relative ''[[Agriotherium|Agriotherium africanum]]'' has also been suggested to share ecomorphological convergences with ''Arctodus simus.''<ref name=":110" /> Together with great size, the two species converged on several adaptations, including a skull with a short broad rostrums, premasseteric fossa on the mandible, possible [[Carnassial|carnassial shears]] (P4 and m1), and long limbs (relative to body length). These features were also shared by other extinct bears (''Agriotherium'', ''[[Huracan (genus)|Huracan]]'' & ''[[Arctotherium|Arctotherium bonariensis]]'').<ref name=":110" /> However, while ''Agriotherium'' & ''Huracan'' have definitive adaptions for meat-heavy diets stemming from a running, predatory lifestyle, ''Arctodus simus'' lacks similar adaptations beyond proportionally longer limbs.<ref name=":16" />

== Interactions with humans ==
[[File:Clovis Point.jpg|thumb|The [[Clovis culture|Clovis people]] are the first known culture to have interacted with ''Arctodus''.|left]]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 tool production, much in the same way as a [[Lehner Mammoth-Kill Site|mammoth carcass]] (~13,000 BP / 11,100 [[Carbon-14|<sup>14</sup>C]] BP ).<ref name=":112">{{Cite book |last1=Arroyo-Cabrales |first1=Joaquin |url=https://www.researchgate.net/publication/305681538 |title=North American ursid (mammalia: ursidae) defaunation from Pleistocene to recent |last2=Johnson |first2=Eileen |last3=Graham |first3=Russell W. |last4=Pérez-Crespo |first4=Victor |date=2016-07-24 |publisher=ICBS Proceedings (Cranium) |volume=33 |pages=51–56 |oclc=1227719621}}</ref><ref>{{Cite journal |last1=Holliday |first1=Vance T. |last2=Johnson |first2=Eileen |last3=Haas |first3=Herbert |last4=Stuckenrath |first4=Robert |date=1983 |title=Radiocarbon Ages from the Lubbock Lake Site, 1950-1980: Framework for Cultural and Ecological Change on the Southern High Plains |journal=Plains Anthropologist |volume=28 |issue=101 |pages=165–182 |doi=10.1080/2052546.1983.11909122 |jstor=25668371 |issn=0032-0447}}</ref> Additionally, other remains of the ''Arctodus simus'' have been found in association with [[Paleo-Indians|Paleo-Indian]] artifacts in [[Sheriden Cave]], Ohio,<ref name=":282" /><ref name=":322" /><ref name="Redmond2">{{cite web |author=Brian G. Redmond |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> and Huntington Dam, Utah,<ref name=":382" /> with an ''A. simus'' [[Metatarsal bones|footbone]] fragment from [[Nez Perce National Historical Park|Spalding]], Idaho also being charred.<ref>{{Cite journal |last1=Kenworthy |first1=Jason P. |last2=Santucci |first2=Vincent L. |last3=McNerney |first3=Michaleen |last4=Snell |first4=Kathryn |date=August 2005 |title=Paleontological Resource Inventory and Monitoring: Upper Columbian Basin Network |url=http://npshistory.com/publications/nepe/paleontological-res-im-2005.pdf |journal=National Park Service (U.S. Department of the Interior) |volume=TIC# D-259 |pages=51}}</ref><ref>{{Cite journal |last=Chadez |first=Jenifer |last2=Sappington |first2=Robert Lee |date=2017-12-01 |title=The Holocene exploitation of mammals in the Clearwater and lower Snake River regions of north-central Idaho |url=https://www.sciencedirect.com/science/article/pii/S2352409X16304138 |journal=Journal of Archaeological Science: Reports |volume=16 |pages=258–265 |doi=10.1016/j.jasrep.2017.09.030 |issn=2352-409X}}</ref> The direct relationship between humans and some associated ''Arctodus'' remains has been debated.<ref>{{Cite journal |last1=Grayson |first1=Donald K. |last2=Meltzer |first2=David J. |date=2002 |title=Clovis Hunting and Large Mammal Extinction: A Critical Review of the Evidence |url=http://link.springer.com/10.1023/A:1022912030020 |journal=Journal of World Prehistory |volume=16 |issue=4 |pages=313–359 |doi=10.1023/A:1022912030020|s2cid=162794300 }}</ref><ref>{{Cite journal |last1=Cannon |first1=Michael D. |last2=Meltzer |first2=David J. |date=2004-10-01 |title=Early Paleoindian foraging: examining the faunal evidence for large mammal specialization and regional variability in prey choice |url=https://www.sciencedirect.com/science/article/pii/S0277379104001052 |journal=Quaternary Science Reviews |volume=23 |issue=18 |pages=1955–1987 |doi=10.1016/j.quascirev.2004.03.011 |bibcode=2004QSRv...23.1955C |issn=0277-3791}}</ref><ref>{{Cite journal |last=Reid |first=Kenneth C. |date=2017-07-20 |title=Idaho beginnings: A review of the evidence |url=https://www.sciencedirect.com/science/article/pii/S1040618216314148 |journal=Quaternary International |series=After Anzick: Reconciling New Genomic Data and Models with the Archaeological Evidence for Peopling of the Americas |volume=444 |pages=72–82 |doi=10.1016/j.quaint.2017.03.040 |issn=1040-6182}}</ref> Human hunting and butchery of large megafauna, particularly mammoths and mastodon, would likely have put people in competition with ''Arctodus simus''. Defense against these large bears and the abandonment of carcasses are plausible outcomes,<ref name=":156" /> along with the possible caching and disposal of carcass remains underwater to mask its odor from ''Arctodus''.<ref>{{Cite journal |last=Kenady |first=Stephen M. |last2=Wilson |first2=Michael C. |last3=Schalk |first3=Randall F. |last4=Mierendorf |first4=Robert R. |date=March 2011 |title=Late Pleistocene butchered Bison antiquus from Ayer Pond, Orcas Island, Pacific Northwest: Age confirmation and taphonomy |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618210001369 |journal=Quaternary International |language=en |volume=233 |issue=2 |pages=130–141 |doi=10.1016/j.quaint.2010.04.013}}</ref>

=== Migration barrier hypothesis ===
In the late 1980s, [[Valerius Geist|Val Geist]] hypothesized that  "specialist, aggressive, competitive [[Rancholabrean]] fauna" such as ''Arctodus'' were a barrier for humans (along with other Siberian megafauna such as moose, grey wolves and brown bears) when migrating into North America (both Beringia and [[Laurentide Ice Sheet|below the ice sheets]]).<ref name="geist">{{citation |last=Geist |first=Valerius |title=The Walking larder: patterns of domestication, pastoralism, and predation |pages=282–294 |year=1989 |editor-last=Clutton-Brock |editor-first=Juliet |archive-url=https://web.archive.org/web/20081216192502/http://www.cnr.uidaho.edu/wlf520/pdf/geist.pdf |chapter=Did Large Predators keep Humans out of North America? |chapter-url=http://www.cnr.uidaho.edu/wlf520/pdf/geist.pdf |publisher=[[Unwin Hyman]] |isbn=0-0444-5013-3 |archive-date=16 December 2008}}</ref> Male ''A. simus'' were the largest and most powerful carnivorous land mammals in North America, with the potential specialization in obtaining and dominating distant and scarce resources. Humans in this hypothesis, though familiar with brown bears, would not have been able to avoid predation or effectively compete with ''Arctodus simus'' and other large Pleistocene North American carnivores, making human expansion difficult in Beringia and impossible south of the ice sheets.<ref name=":156" /><ref name=":272" /><ref name=":36" /> However, this theory has [[Fringe theory|never been accepted]] by anthropologists.<ref name=":36" /> Paul Matheus argues that there were negligible ecological differences across the mammoth steppe, and that humans successfully competed against and even hunted territorial [[cave bear]]s, [[cave hyena]]s, [[Panthera spelaea|cave lions]], leopards, tigers and wolves in Eurasia before reaching eastern Beringia, making the solitary ''Arctodus'' an unlikely impediment to expansion.<ref name=":36">{{Cite book |last=Paul |first=Matheus |url=https://www.fulcrum.org/concern/monographs/9z9031660 |title=People and Wildlife in Northern North America: Essays in honor of R. Dale Guthrie |date=2001 |publisher=BAR Publishing |isbn=978-1-4073-5292-3 |editor-last=Gerlach |editor-first=S. Craig |pages=79–101 |language=en |chapter=Pleistocene carnivores and humans in eastern Beringia: did short-faced bears really keep people out of North America? |doi=10.30861/9781841712369 |editor-last2=Murray |editor-first2=Maribeth S.}}</ref> Indeed, new dates establish an extended co-existence of humans and megafauna such as ''Arctodus'' across North America.<ref name=":26" /><ref name=":37">{{Cite journal |last1=Boëda |first1=Eric |last2=Gruhn |first2=Ruth |last3=Vialou |first3=Agueda Vilhena |last4=Aschero |first4=Carlos |last5=Vialou |first5=Denis |last6=Pino |first6=Mario |last7=Gluchy |first7=Maria |last8=Pérez |first8=Antonio |last9=Ramos |first9=Marcos Paulo |date=2021-01-02 |title=The Chiquihuite Cave, a Real Novelty? Observations about the Still-ignored South American Prehistory |url=https://www.tandfonline.com/doi/full/10.1080/20555563.2020.1851500 |journal=PaleoAmerica |language=en |volume=7 |issue=1 |pages=1–7 |doi=10.1080/20555563.2020.1851500 |s2cid=230533453 |issn=2055-5563}}</ref><ref name=":38" /><ref name=":40">{{Cite journal |last=Gruhn |first=Ruth |date=2023-07-03 |title=An Anthropological Conception of the Initial Peopling of the Americas |url=https://www.tandfonline.com/doi/full/10.1080/20555563.2023.2278948 |journal=PaleoAmerica |language=en |volume=9 |issue=3 |pages=167–173 |doi=10.1080/20555563.2023.2278948 |s2cid=265285459 |issn=2055-5563}}</ref>

==== Beringia ====
[[File:Ccsm4_beringia_lgm_tundratypes_by_temperature_1.png|thumb|313x313px|[[Beringia]] during the [[Last Glacial Maximum]].]]
Humans migrated to North America via the Siberian [[mammoth steppe]], arriving at [[Beringia|Eastern Beringia]] (Alaska and the Yukon). However, the migration was halted at the [[Wisconsin glaciation|North American Ice Sheet]], which separated Beringia and southern North America for most of the Late Pleistocene.<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 |issn=0011-3204 |s2cid=149080106}}</ref> Both humans and ''Arctodus'' are first dated to ~50,000 BP in Beringia, both from sites in the Yukon, and co-existed until ''Arctodus'' went extinct in Beringia ~23,000 BP during the [[Last Glacial Maximum]]. This co-existence continued through the regional extinction of other Beringian predators such as cave lions, brown bears and [[Homotherium|saber-tooth cats]].<ref name=":19" /> Important sites of pre-LGM human occupation in Beringia include [[Old Crow Flats]] & the [[Klondike, Yukon|Klondike]],<ref>{{Cite journal |last1=Harington |first1=C. R. |last2=Morlan |first2=Richard E. |date=2002 |title=Evidence for Human Modification of a Late Pleistocene Bison (Bison sp.) Bone from the Klondike District, Yukon Territory, Canada |journal=Arctic |volume=55 |issue=2 |pages=143–147 |doi=10.14430/arctic698 |jstor=40512447 |issn=0004-0843|doi-access=free }}</ref><ref>{{Cite journal |last1=Holen |first1=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 |journal=Arctic |volume=70 |issue=2 |pages=141–150 |doi=10.14430/arctic4645 |jstor=26379757 |issn=0004-0843|doi-access=free }}</ref> [[Kuparuk River|Kuparuk River Valley]],<ref>{{Cite journal |last1=Goebel |first1=Ted |last2=Hoffecker |first2=John F. |last3=Graf |first3=Kelly E. |last4=Vachula |first4=Richard S. |date=June 2022 |title=Archaeological reconnaissance at Lake E5 in the Brooks Range, Alaska and implications for the early human biomarker record of Beringia |journal=Quaternary Science Reviews |language=en |volume=286 |page=107553 |doi=10.1016/j.quascirev.2022.107553|bibcode=2022QSRv..28607553G |s2cid=248736952 |doi-access=free }}</ref> & the [[Bluefish Caves]].<ref>{{Cite journal |last1=Bourgeon |first1=Lauriane |last2=Burke |first2=Ariane |last3=Higham |first3=Thomas |date=2017-01-06 |title=Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada |journal=PLOS ONE |language=en |volume=12 |issue=1 |pages=e0169486 |doi=10.1371/journal.pone.0169486 |issn=1932-6203 |pmc=5218561 |pmid=28060931|bibcode=2017PLoSO..1269486B |doi-access=free }}</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 |page=102969 |doi=10.1016/j.jasrep.2021.102969 |bibcode=2021JArSR..37j2969B |s2cid=234816694 |issn=2352-409X}}</ref>

==== Contiguous North America ====
The human colonization of North America south of the ice sheets further disproves the idea that ''Arctodus'' was a migration barrier. The earliest universally accepted pre-Clovis site south of Beringia are the [[White Sands National Park#Native people|White Sands footprints]] in New Mexico, dated to ~22,000 cal. BP.<ref name=":26">{{Cite journal |last1=Pigati |first1=Jeffrey S. |last2=Springer |first2=Kathleen B. |last3=Honke |first3=Jeffrey S. |last4=Wahl |first4=David |last5=Champagne |first5=Marie R. |last6=Zimmerman |first6=Susan R. H. |last7=Gray |first7=Harrison J. |last8=Santucci |first8=Vincent L. |last9=Odess |first9=Daniel |last10=Bustos |first10=David |last11=Bennett |first11=Matthew R. |date=2023-10-06 |title=Independent age estimates resolve the controversy of ancient human footprints at White Sands |url=https://www.science.org/doi/10.1126/science.adh5007 |journal=Science |language=en |volume=382 |issue=6666 |pages=73–75 |doi=10.1126/science.adh5007 |pmid=37797035 |bibcode=2023Sci...382...73P |s2cid=263672291 |issn=0036-8075}}</ref> Other pre-[[Last Glacial Maximum|LGM]] sites across the Americas, such as [[Chiquihuite cave|Chiquihuite Cave]],<ref>{{Cite journal |last1=Ardelean |first1=Ciprian F. |last2=Becerra-Valdivia |first2=Lorena |last3=Pedersen |first3=Mikkel Winther |last4=Schwenninger |first4=Jean-Luc |last5=Oviatt |first5=Charles G. |last6=Macías-Quintero |first6=Juan I. |last7=Arroyo-Cabrales |first7=Joaquin |last8=Sikora |first8=Martin |last9=Ocampo-Díaz |first9=Yam Zul E. |last10=Rubio-Cisneros |first10=Igor I. |last11=Watling |first11=Jennifer G. |last12=de Medeiros |first12=Vanda B. |last13=De Oliveira |first13=Paulo E. |last14=Barba-Pingarón |first14=Luis |last15=Ortiz-Butrón |first15=Agustín |date=2020-08-06 |title=Evidence of human occupation in Mexico around the Last Glacial Maximum. |journal=Nature |volume=584 |issue=7819 |pages=87–92 |doi=10.1038/s41586-020-2509-0 |pmid=32699412 |bibcode=2020Natur.584...87A |s2cid=256819465 |url=https://www.repository.cam.ac.uk/handle/1810/312474 |issn=0028-0836}}</ref><ref name=":37" /> [[Hueyatlaco|Valsequillo]],<ref>{{Cite journal |last=Pichardo |first=M. |date=1997 |title=Valsequillo biostratigraphy: New evidence for Pre-Clovis date |journal=Anthropologischer Anzeiger |volume=55 |issue=3/4 |pages=233–246 |doi=10.1127/anthranz/55/1997/233 |jstor=29540729 |issn=0003-5548}}</ref> El Cedral,<ref>{{Cite journal |last1=Gonzalez |first1=Sofia |last2=Huddart |first2=David |date=2008 |title=The Late Pleistocene Human Occupation of Mexico |url=https://www.researchgate.net/publication/265490787 |journal=FUMDHAMentos VII |via=ResearchGate}}</ref> Santa Elina,<ref name=":38">{{Cite journal |last1=Pansani |first1=Thais R. |last2=Pobiner |first2=Briana |last3=Gueriau |first3=Pierre |last4=Thoury |first4=Mathieu |last5=Tafforeau |first5=Paul |last6=Baranger |first6=Emmanuel |last7=Vialou |first7=Águeda V. |last8=Vialou |first8=Denis |last9=McSparron |first9=Cormac |last10=de Castro |first10=Mariela C. |last11=Dantas |first11=Mário A. T. |last12=Bertrand |first12=Loïc |last13=Pacheco |first13=Mírian L. A. F. |date=2023-07-12 |title=Evidence of artefacts made of giant sloth bones in central Brazil around the last glacial maximum |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=290 |issue=2002 |doi=10.1098/rspb.2023.0316 |issn=0962-8452 |pmc=10336383 |pmid=37434527}}</ref> [[Gault (archaeological site)|Gault]],<ref name=":41">{{Cite journal |last=Gruhn |first=Ruth |date=2020-08-06 |title=Evidence grows that peopling of the Americas began more than 20,000 years ago |url=https://www.nature.com/articles/d41586-020-02137-3 |journal=Nature |language=en |volume=584 |issue=7819 |pages=47–48 |doi=10.1038/d41586-020-02137-3 |pmid=32699366 |bibcode=2020Natur.584...47G |s2cid=220717778 |issn=0028-0836}}</ref> and [[Hartley Mammoth Site]],<ref name=":42">{{Cite journal |last1=Rowe |first1=Timothy B. |last2=Stafford |first2=Thomas W. |last3=Fisher |first3=Daniel C. |last4=Enghild |first4=Jan J. |last5=Quigg |first5=J. Michael |last6=Ketcham |first6=Richard A. |last7=Sagebiel |first7=J. Chris |last8=Hanna |first8=Romy |last9=Colbert |first9=Matthew W. |date=2022 |title=Human Occupation of the North American Colorado Plateau ∼37,000 Years Ago |journal=Frontiers in Ecology and Evolution |volume=10 |doi=10.3389/fevo.2022.903795 |issn=2296-701X |doi-access=free }}</ref> affirm that humans proliferated alongside megafauna (such as ''Arctodus'') in southern North America for more than ten thousand years.<ref name=":37" /><ref name=":40" /><ref name=":41" /><ref name=":42" /><ref>{{Citation |last=Gruhn |first=Ruth |title=To the End of the World: Southern Patagonia in Models of the Initial Peopling of the Western Hemisphere |date=2022 |url=https://link.springer.com/10.1007/978-3-030-92503-1_16 |work=Archaeology of Piedra Museo Locality |series=The Latin American Studies Book Series |pages=449–456 |editor-last=Miotti |editor-first=Laura |access-date=2023-12-11 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-92503-1_16 |isbn=978-3-030-92502-4 |s2cid=246571694 |editor2-last=Salemme |editor2-first=Monica |editor3-last=Hermo |editor3-first=Darío}}</ref> Humans were definitively widespread across the Americas by at least 15,000 BP.<ref name=":156" /><ref name=":40" />

== Extinction ==
[[File:Arctodus simus skeletal.jpg|thumb|Skeletal reconstruction of ''Arctodus simus.'']]''Arctodus pristinus'' went extinct in the late Irvingtonian (300,000 years ago),<ref name=":02" /> being last recorded from the Coleman 2A site, Florida.<ref>{{Citation |last=Karrow |first=P.F. |title=Middle Pleistocene (early Rancholabrean) vertebrates and associated marine and non-marine invertebrates from Oldsmar, Pinellas County, Florida |date=1996-12-31 |work=Palaeoecology and Palaeoenvironments of Late Cenozoic Mammals |pages=97–133 |url=https://www.degruyter.com/document/doi/10.3138/9781487574154-009/html |access-date=2024-01-23 |publisher=University of Toronto Press |doi=10.3138/9781487574154-009 |isbn=978-1-4875-7415-4 |last2=Morgan |first2=G.S. |last3=Portell |first3=R. W. |last4=Simons |first4=E. |last5=Auffenberg |first5=K.}}</ref> With the extinction of ''Arctodus pristinus'', ''Arctodus simus'' became the final representative of the genus. ''Arctodus simus'' went extinct around 12,800 years ago, and is one of the most recently dated megafauna to go extinct in North America, being reliably dated to within the [[Late Pleistocene extinctions|Pleistocene-Holocene boundary]] (13,800 [[Before Present|BP]] - 11,400 BP).<ref name=":442">{{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 |s2cid=128868400}}</ref><ref name=":51">{{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 |issn=0027-8424 |pmc=2791611 |pmid=19934040 |bibcode=2009PNAS..10620641F |doi-access=free}}</ref><ref>{{Cite journal |last=Haynes |first=Gary |date=2013-02-08 |title=Extinctions in North America's Late Glacial landscapes |url=https://www.sciencedirect.com/science/article/pii/S104061821000296X |journal=Quaternary International |series=Peopling the last new worlds: the first colonisation of Sahul and the Americas |volume=285 |pages=89–98 |doi=10.1016/j.quaint.2010.07.026 |bibcode=2013QuInt.285...89H |issn=1040-6182}}</ref> Both local and regionalized dietary flexibility has been a factor suggested for the species' longevity.<ref name=":142" />

Various factors, including the depletion in number of large herbivores,<ref name=":34" /><ref name=":1622" /> the diminishing nutritional quality of plants during climate change, and competition with fellow omnivores (humans and brown bears) for food resources, have been suggested as the cause of ''Arctodus simus''<nowiki/>' extinction.<ref name=":112" /> However, multiple studies put doubt on brown bears being culpable in ''Arctodus simus''<nowiki/>' extinction, with the brown bear being more of an ecological replacement that was more adaptable to change.<ref name=":92" /><ref name=":156" /><ref name=":1622" /> Moreover, there is no systematic 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=":156" /> Additionally, dental wear evidence from [[La Brea Tar Pits|Rancho La Brea]] does not suggest that food shortages were to blame for the demise large bodied [[carnivora]]ns such as ''Arctodus simus''.<ref name="Donohue2" />

=== Climate change ===
Of the factors discussed, 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]]. [[Tsuga heterophylla|Closed forests]] continued to expand in the [[Greenlandian|early Holocene]]. Even though ''Arctodus simus'' was not restricted to open areas and could inhabit 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 extinction of ''Arctodus simus'', along with many other megafauna.<ref name=":156" />

=== Low genetic diversity ===
[[File:Arctodus simus (4252855106).jpg|thumb|201x201px|Low genetic diversity could have hastened ''Arctodus''<nowiki/>' extinction.]]
''Arctodus simus'' had a very low level of genetic diversity from most sampled specimens, albeit a sample with a Beringian and temporal bias (<44,000 BP). A loss and/or replacement of mitochondrial DNA lineages before the Last Glacial Maximum, and decrease in population size from a previously genetically diverse population, has been noted in a variety of Eurasian and American Late Pleistocene megafauna.<ref name=":49" /><ref>{{Cite journal |last1=Mitchell |first1=Kieren J. |last2=Bover |first2=Pere |last3=Salis |first3=Alexander T. |last4=Mudge |first4=Caitlin |last5=Heiniger |first5=Holly |last6=Thompson |first6=Mary |last7=Hockett |first7=Bryan |last8=Weyrich |first8=Laura S. |last9=Cooper |first9=Alan |last10=Meachen |first10=Julie A. |date=November 2021 |title=Evidence for Pleistocene gene flow through the ice-free corridor from extinct horses and camels from Natural Trap Cave, Wyoming |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618221005589 |journal=Quaternary International |volume=647-648 |language=en |pages=71–80 |doi=10.1016/j.quaint.2021.11.017|s2cid=244706923 }}</ref> That the individual from Sheriden Cave, Ohio was very closely related to Beringian specimens may further support this idea, as these populations had possibly been isolated from before the Last Glacial Maximum (tens of thousands of years).<ref name=":49">{{Cite thesis |last=Bray |first=Sarah C. E. |date=September 2010 |title=Mitochondrial DNA Analysis of the Evolution and Genetic Diversity of Ancient and Extinct Bears |url=https://digital.library.adelaide.edu.au/dspace/bitstream/2440/66285/8/02whole.pdf |publisher=School of Environmental and Earth Sciences, University of Adelaide |pages=214 (230)}}</ref>

A lack of genetic diversity has been attributed to a reduced ability to adapt to environmental conditions. Small population sizes may be characteristic of tremarctine bears- the spectacled bear, while having low levels of genetic diversity, has no signs of a recent genetic bottleneck. However, brown bears had diverse, [[Sympatry|sympatric]] source populations in Eurasia, allowing for repopulations/reinvasions into the Americas. If ''Arctodus simus'' experienced genetic bottlenecks or local extinctions prior to the Last Glacial Maximum, ''Arctodus'' would have been unable to supplement their reduced genetic diversity with new migrants like the brown bear could, making them vulnerable to extinction.<ref name=":49" />

=== Last dates ===
The youngest date for ''Arctodus simus'' is circa 12,700 BP from [[San Antonio|Friesenhahn Cave]], Texas, calibrated from 10,814 ± 55 [[radiocarbon year]]s ([[Carbon-14|<sup>14</sup>C]] 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 and 11,021 <sup>14</sup>C 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 <sup>14</sup>C BP) and is therefore considered reliable.<ref name=":12" /><ref name=":442" />

== History of research ==

=== "Super predator" hypothesis ===
[[File:DSC09100 - Extinct Bear (37221999825).jpg|thumb|Skeletal reconstruction of ''Arctodus simus'' at the [[Royal Ontario Museum]], Toronto.]]
One past proposal envisaged ''A.&nbsp;simus'' as a brutish predator that overwhelmed very large but slow megafauna with its great physical strength.<ref name=":212" /> However, despite being very large, its limbs were too [[gracile]] for such an attack strategy,<ref name=":212" /><ref name=":222" /><ref name=":36" /> significantly more gracile so than ''[[Arctotherium|Arctotherium angustidens]]'' at that.<ref name=":20" />

Due to their long legs, an alternative hypothesis suggested by [[Björn Kurtén]] is that it may have hunted by running down Pleistocene herbivores such as [[wild horse]]s and [[saiga antelope]]s, an idea that at one time earned it the name "running bear".<ref name=":1622" /><ref name="Figueiridio_et_al_20102" /><ref name=":0" /> However, during pursuit of speedy game animals, the bear's sheer physical mass, inflexible [[Intertransversarii|spine]] 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. Correspondingly, although a  {{Convert|700|kg|lb|abbr=on}} ''Arctodus'' may have been able to reach a maximum speed of {{Convert|51|km/h|mph}}, all modern bears have maximum speeds significantly lower than mass-based calculations for speed. As a result, paleontologist Paul Matheus suggests that ''Arctodus''<nowiki/>' top speed was {{Convert|40-45|km/h|mph|abbr=on}}. ''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="Simus2" /><ref name=":110" /><ref name=":212" /> Proportionally taller legs, a short trunk, proximally elongated limbs, a stride which had little to no unsupported intervals, small and laterally-orientated eyes, and proportionally short canines ill-suited for spinal and tracheal attacks further complicated ambush hunting as a lifestyle for ''Arctodus''.<ref name=":132" /><ref name=":110" /><ref name=":16" />

Furthermore, the lack of definitive 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_20102" /><ref name="Meloro 133–146" /><ref name=":110" /><ref name=":22" /> The anatomical requirements for a large, cursorial, hyper-carnivorous bear are present in ''[[Huracan (genus)|Huracan]]'' and ''Agriotherium'', but not ''Arctodus''.<ref name=":16" /><ref>{{Cite journal |last1=Stynder |first1=Deano D. |last2=Kupczik |first2=Kornelius |date=September 2012 |title=Tooth Root Morphology in the Early Pliocene African Bear Agriotherium africanum (Mammalia, Carnivora, Ursidae) and its Implications for Feeding Ecology |url=http://link.springer.com/10.1007/s10914-012-9218-x |journal=Journal of Mammalian Evolution |language=en |volume=20 |issue=3 |pages=227–237 |doi=10.1007/s10914-012-9218-x |issn=1064-7554 |s2cid=254692536}}</ref> Adaptations for predatory behavior are highly divergent in ursids versus other carnivorans, with features such as a short rostrum and long carnassials not being indicative of a predatory lifestyle in ''Arctodus''.<ref name=":22" /> Although the only living [[Hypercarnivore|hyper-carnivorous]] [[Bear|ursid]], the polar bear, also lacks [[Carnassial|carnassial shears]], the species' specialization on small prey and reliance on [[blubber]] (rather than coarser flesh) invalidates a comparison with ''Arctodus''.<ref name=":132" /><ref name=":110" /><ref name=":22" /> Therefore, carnivory was limited to the regular scavenging of carcasses and opportunistic hunting, as is the case with the modern brown bear.<ref name=":1622" /><ref name="Figueiridio_et_al_20102" /><ref name=":110" />

=== Specialist kleptoparasite vs Omnivore ===
[[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|[[Mastodon]] arm bone from the [[Snowmastodon site|Snowmastodon]] site with predator damage at the [[Denver Museum of Nature & Science]] in [[Denver]], Colorado.]]
The idea that ''Arctodus'' was an obligate [[Kleptoparasitism|kleptoparasite]] was most notably proposed by Paul Matheus.<ref name="Simus2" /> Under this model, ''A.&nbsp;simus'' was ill-equipped to be an active predator, 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=":110" /> 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=":212" /> Matheus calculated that with a [[Hypercarnivore|hyper-carnivorous]] diet, a {{Convert|700|kg|lb|abbr=on}} Beringian ''Arctodus'' would need to consume ~{{Convert|5853|kg|lb}} of meat per year- the equivalent of 12 [[bison]], 44.6 [[Wild horse|horses]], or 2 [[woolly mammoth]]s (adjusted for the non-edible portions of the body). Therefore, ''Arctodus'' would have had to obtain {{Convert|100|kg|lb|abbr=on}} of flesh/edible [[carrion]] every 6.25 days ({{Convert|16|kg|lb|1|abbr=on}} per day).<ref name="Simus2" /><ref name=":272" /><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'') |url=https://www.academia.edu/751564 |journal=C R Acad Sci |volume=320 |pages=779–784}}</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=":110" /> Additionally, strengthened tooth enamel in ''Arctodus'' may have evolved to crack bone.<ref name=":21" /> 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]]s such as [[bison]], whose mortality peaks in late winter to early spring).<ref name=":272" /> Finally, that ''Arctodus'' and the [[cave hyena]] did not spread into [[Siberia]] and [[North America]] respectively suggests some form of [[Competitive exclusion principle|competitive exclusion]] was at play.<ref name=":292" />

==== Rebuttal ====
[[File:Shortfacedbear-1070375.jpg|thumb|226x226px|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''.]]

The kleptoparasite hypothesis has been repeatedly challenged. 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_20102" /> Specialized 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 in 2013 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 ranging from omnivory to almost pure herbivory.<ref name=":132" /><ref name="Donohue2" />

Additionally, 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 hard 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 various specimens of ''A. simus,'' other than the strong wear facets of old individuals.<ref name="Figueiridio_et_al_20102" /> Instead, recovered dental damage (incisor wear, dental calculus & cavities) is herbivorous in origin.<ref name=":2" /><ref name=":142" /><ref name=":156" /> Moreover, researchers in 2015 reviewing links between canine breakage, microwear texture patterns and carnivorans from La Brea found that ''A. simus'' consumed foods softer yet tougher than black bears and polar bears, avoided hard/brittle foods such as bone, and reaffirmed affinities between ''A. simus'' and modern, largely herbivorous spectacled bears.<ref name=":172" /> In addition to hyenas, many other fauna did not cross the Rancholabrean [[Beringia|Beringian gap]], such as the [[American badger]], ''Bootherium'' and the [[Woolly rhinoceros|woolly rhino]]).<ref>{{Cite journal |last=Stuart |first=Anthony J. |last2=Lister |first2=Adrian M. |date=2012-09-19 |title=Extinction chronology of the woolly rhinoceros Coelodonta antiquitatis in the context of late Quaternary megafaunal extinctions in northern Eurasia |url=https://www.sciencedirect.com/science/article/pii/S0277379112002326 |journal=Quaternary Science Reviews |volume=51 |pages=1–17 |doi=10.1016/j.quascirev.2012.06.007 |issn=0277-3791}}</ref><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 |last1=Blinnikov |first1=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 |bibcode=2011QSRv...30.2906B |doi=10.1016/j.quascirev.2011.07.002 |issn=0277-3791}}</ref>

Furthermore, the relative lack of ''Arctodus'' remains at [[predator trap]]s such as the La Brea Tar Pits, suggests that ''Arctodus'' did not regularly compete for carcasses.<ref name=":142" /> Although La Brea has produced more ''Arctodus simus'' specimens than any other site, ''Arctodus'' represents only 1% of all carnivorans in the pits.<ref name=":172" /> While more abundant than [[brown bear]]s and [[American black bear|black bears]], ''Arctodus'' was calculated to its baseline continental abundance, contrasting with the overabundance of other large carnivorans.<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 |bibcode=2012PPP...329..118M |doi=10.1016/j.palaeo.2012.02.022 |issn=0031-0182}}</ref> A similar rate (~0.9%) of relative abundance was calculated for ''Arctodus'' compared to other [[megafauna]] at the [[Natural Trap Cave]] in [[Wyoming]] by 1993.<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> Additionally, 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=":312" /> Further evidence comes from the evolution of brain size relative to body size- bears with high caloric diets and which do not exhibit dormancy showed a weak but significant correlation with bigger relative brain size. ''Arctodus simus'' plotted in between the likely hypercarnivorous ''[[Cephalogale]],'' and the almost exclusively herbivorous Eurasian cave bear and ''[[Indarctos]],'' suggesting omnivory.<ref>{{Cite journal |last=Veitschegger |first=Kristof |date=2017-06-05 |title=The effect of body size evolution and ecology on encephalization in cave bears and extant relatives |journal=BMC Evolutionary Biology |volume=17 |issue=1 |page=124 |bibcode=2017BMCEE..17..124V |doi=10.1186/s12862-017-0976-1 |issn=1471-2148 |pmc=5460516 |pmid=28583080 |doi-access=free}}</ref>

==See also==
* ''[[Arctotherium]]''
* ''[[Agriotherium]]''
* [[Cave bear|Eurasian cave bear]]
* [[Quaternary extinction|Quaternary Extinction Event]]
* ''[[Wild New World]]''

==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]]
[[Category:Extinct animals of Canada]]