{{Short description|Extinct genus of bears}} {{Automatic taxobox | fossil_range = {{Fossil range|2.58|0.012}}<small> Pleistocene</small> | image = Arctodus simus Page.jpg | image_caption = ''A. simus'' from the La Brea Tar Pits | taxon = Arctodus | authority = Leidy, 1854 | type_species = {{extinct}}'''''Arctodus pristinus''''' | type_species_authority = Leidy, 1854 | subdivision_ranks = Other species | subdivision = *{{extinct}}''A. simus'' {{small|(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|Hay 1902}} |''Arctotherium pristinum'' {{small|Cope 1895}} |''Ursus haplodon'' {{small|Cope 1896}} |''Tremarctos haplodon'' {{small|Trouessart 1897}} }} {{collapsible list|bullets=true|title={{small|synonyms of ''A. simus''}} |''Arctodus nebrascensis'' {{small|Berger 1930}} |''Arctotherium californicum'' {{small|Merriam 1911}} |''Arctotherium simum'' {{small|Cope 1879}} |''Arctotherium yukonense'' {{small|Lambe 1911}} |''Dinarctotherium merriami'' {{small|Barbour 1916}} |''Tremarctotherium simum'' {{small|Gidley 1928}} }} }}'''''Arctodus''''' is an extinct genus of short-faced bears that inhabited North America during the Pleistocene (about 2.58 Mya until 12,800 years ago). The two recognized species are 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 best-known members of North America's extinct Ice Age 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 carnivorans that has ever existed. ''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|abbr=on}}, and males around {{convert|800|kg|abbr=on}}. The largest males stood at {{convert|1.67|m|1|abbr=on}} at the shoulder, and up to {{convert|3.4|m||abbr=on}} tall on their rear legs. Studies suggest that ''A. simus'' browsed on C<sub>3</sub> vegetation and consumed browsing herbivores such as deer, camelids, and tapir. The species preferred temperate open woodlands, but was adaptable, 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, but was restricted to the Pleistocene. ''A. pristinus'' went extinct around 300,000 years ago, with ''A. simus'' disappearing about 12,800 years ago in the Late Pleistocene extinctions. The cause behind these extinctions is unclear, but in the case of ''A. pristinus'', was likely due to climate change and competition with other ursids, such as the black bear and ''Tremarctos floridanus''. ''A. simus'' likely went extinct due to ecological collapse disrupting the vegetation and prey on which it relied.
==Taxonomy== [[File:Arctodus pristinus mandible ANSP 98.jpg|right|thumb|Partial mandible of ''A. pristinus'' uncovered from Port Kennedy Cave]] ''Arctodus'' was first described by Joseph Leidy in 1854, with finds of ''A. pristinus'' from the Ashley Phosphate Beds, South Carolina.<ref name="Florida Museum-2017">{{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="Emslie-1995" /><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 ''A. simus'' were found in the Potter Creek Cave, Shasta County, California, by J. A. Richardson in 1878, and were initially described as ''Arctotherium simum'' by Edward Drinker Cope in 1879.<ref name="Cope E. D.-1879">{{Cite journal |last=Cope E. D. |year=1879 |title=The cave bear of California |journal=American Naturalist |volume=13 |page=791}}</ref><ref name="Feranec-2009">{{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="Merriam-1925">{{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="Richards-1996">{{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.|url-access=subscription }}</ref> The (lost) holotype and neotype of ''A. pristinus'' are both from South Carolina.<ref name="Sanders-2002" />
In the 19th and early 20th centuries, specimens of ''Arctodus'' were occasionally referred to ''Arctotherium'', and vice versa.<ref name="Merriam-1925" /><ref name=":8">{{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><ref name=":5">{{Cite journal |last1=Gidley |first1=James W. |last2=Gazin |first2=Charles Lewis |date=1938 |title=The Pleistocene vertebrate fauna from Cumberland Cave, Maryland |url=http://hdl.handle.net/10088/10106 |journal=Smithsonian Institution United States National Museum |language=en |volume=Bulletin 171 |hdl=10088/10106 |issn=0362-9236 |via=Smithsonian Libraries and Archives}}</ref><ref name=":20" /> Today, however, the genera are not considered to have overlapped, with the closest point of contact being México, with the giant ''Arctodus simus'' in Valsequillo, Puebla,<ref name="Richards-1996" /><ref name="Ferrusquía-Villafranca-2010">{{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|url-access=subscription }}</ref><ref name=":9">{{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|url-access=subscription }}</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|article-number=20190148|doi=10.1098/rsbl.2019.0148 |pmc=6548739|pmid=31039726}}</ref> Other early researchers believed ''Arctodus'' to be a sister lineage of the 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="Cope E. D.-1879" /><ref name=":10">{{Cite web |title=Big Pine Citizen 2 March 1918 — California Digital Newspaper Collection |url=https://cdnc.ucr.edu/?a=d&d=BPC19180302.2.28 |access-date=2024-07-18 |website=cdnc.ucr.edu}}</ref><ref name=":5" /><ref name=":20" /> ''Arctodus'' should not be mistaken for the similarly large Eurasian cave bear (''Ursus spelaeus''). As an ursine, the Eurasian cave bear last shared a common ancestor with the tremarctine ''Arctodus'' ''circa'' 13.4 Mya.<ref name="Pedersen 2728–2736.e8" /><ref name=":13">{{Cite journal |last=Saremi |first=Nedda F. |date=September 2020 |title=A Genomic Approach to Studying the Evolutionary Consequences of Population Declines, Chapter 2: Tremarctine bears of present and past|url=https://escholarship.org/content/qt8f63q6wg/qt8f63q6wg_noSplash_1cb133996a69d42cb301dce3d6461d91.pdf?t=qiwqjp |journal=Biomolecular Engineering and Bioinformatics, University of Santa Cruz (PHD Thesis) |pages=86–142}}</ref>
Fossils of ''Arctodus pristinus'' can be confused with the similarly sized, partially contemporaneous short-faced bear, ''Tremarctos floridanus''.<ref name="Florida Museum-2017" /> ''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="Emslie-1995" /> 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 ''A. simus'' specimens.<ref name="Richards-1996" /> Beyond standard differences between tremarctine and ursine bears, ''A. simus'' has a more anterior protocone and extended enamel ridge forming a shearing blade on the maxillary P4. The molars are also shorter and broader in ''Arctodus'' than brown bears.<ref name="Steffen-2018">{{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 75px |2={{Clade |1=Ursinae 75px |2={{Clade |label1=Tremarctinae (short-faced bears) |1={{Clade |1={{dagger}}''Plionarctos'' |2={{Clade |1={{dagger}}'''''Arctodus''''' |2={{Clade |1=''Tremarctos'' 75px |2={{dagger}}''Arctotherium'' }} }} }} }} }} }} }} }}|title=Tremarctinae within Ursidae|align=left}} ''Arctodus'' belongs to the subfamily Tremarctinae, which appeared in North America during the late Miocene epoch in the form of ''Plionarctos''. The medium-sized ''Arctodus pristinus,'' ''Tremarctos floridanus'', and ''Arctotherium'' species evolved from ''Plionarctos'' in the Blancan age of North America.<ref name="Emslie-1995">{{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 |issue=15 |pages=501–514 |doi=10.58782/flmnh.hduf9651 |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-15.pdf |s2cid=168164209 }}</ref><ref>{{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 |bibcode=2008NJGPA.250....1S |url=http://sedici.unlp.edu.ar/handle/10915/5361 }}</ref><ref name="Schubert-2010a">{{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 between 5.5 million and 4.8 million years ago,<ref name="Pedersen 2728–2736.e8" /><ref name=":13" /><ref name="Mitchell-2016" /> around the Miocene-Pliocene boundary, when tremarctine bears, along with other ursids, experienced an explosive radiation in diversity, as C<sub>4</sub> vegetation (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'' first appears in the early Late Blancan (Early Pleistocene), with the earliest finds being ''A. pristinus'' from the Kissimmee River 6 and Santa Fe River 1 sites in Florida,<ref name="Florida Museum-2017" /><ref name="Emslie-1995" /><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 Natural History |volume=45 |issue=4 |pages=271–311|doi=10.58782/flmnh.pkqn7297 }}</ref> dated from 2.6-2.3 Mya,<ref>{{Cite journal |last=Hulbert |first=Richard |date=2010-09-20 |title=A new early Pleistocene tapir (Mammalia: Perissodactyla) from Florida, with a review of Blancan tapirs from the state |url=https://flmnhbulletin.com/index.php/flmnh/article/view/flmnh-vol49-no3 |journal=Bulletin of the Florida Museum of Natural History |language=en |volume=49 |issue=3 |pages=67–126 |doi=10.58782/flmnh.ezjr9001 |issn=2373-9991}}</ref> and ''Arctodus sp.'' from 111 Ranch (~2.6 Mya) and San Simon (about 2.2 Mya) in Arizona,<ref name=":4" /><ref name=":6">{{Cite journal |last=Thrasher |first=Larry |date=July 2022 |title=Fossils and Age Relationships of the Late Pliocene and Early Pleistocene (Blancan) 111 Ranch Beds and Bear Springs Wash Beds, Graham County, Arizona |url=https://www.researchgate.net/publication/362191500 |journal=Late Cenozoic Vertebrate Paleontology: Tribute to Arthur H. Harris. New Mexico Museum of Natural History and Science Bulletin |volume=88 |via=ResearchGate}}</ref><ref>{{Cite journal |last1=Morgan |first1=Gary S. |last2=White Jr. |first2=Richard S. |date=2005 |title=Miocene and Pliocene vertebrates from Arizona |url=https://www.researchgate.net/publication/40661398 |journal=Vertebrate Paleontology in Arizona. New Mexico Museum of Natural History and Science Bulletin |volume=29 |via=ResearchGate}}</ref> and La Union in New Mexico (Mesilla Fauna B, 2.2-1.8 Mya).<ref>{{Cite conference|last1=Morgan |first1=Gary S. |last2=Lucaas |first2=Spencer G. |date=October 12–14, 2001 |title=Plioi-Pleistocene Stratigraphy and Geomorphology of the Central Part of the Albuquerque Basin |url=https://geoinfo.nmt.edu/publications/openfile/downloads/400-499/454/papers/OFR454D_PDF/H_OFR454D_Morgan_PlioceneBiostratigraphy_reprint.pdf |journal=Friends of the Pleistocene, Rocky Mountain-Cell, 45th Field Conference |chapter=Summary of Blancan and Irvingtonian (Pliocene and Early Pleistocene) Mammalian Biochronology of New Mexico (NMBGMR OFR454D) |pages=D1-D4 (B29-B30) |access-date=June 17, 2025}}</ref> This appearance coincides with the start of the Quaternary glaciation, and the second phase of the great American biotic interchange, with the first records of the main South American faunal wave into the United States.<ref name=":6" /> ''A. pristinus'' was mostly restricted to the more densely forested thermal enclave in 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="Russell-2009">{{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 Southeastern United States |journal=Biological Reviews |volume=84 |issue=2 |pages=173–202 |doi=10.1111/j.1469-185X.2008.00069.x |pmid=19391200 |bibcode=2009BioRv..84..173R |s2cid=9609391 }}</ref> with the greatest concentration of fossils being in Florida.<ref name="Emslie-1995" />
During the early Irvingtonian faunal stage, a western population of ''A. pristinus'' evolved into the enormous ''A. simus'',<ref name="Richards-1996" /><ref name="Bell-2004">{{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> although an anomalous Blancan record of ''A. simus'' exists from the Palm Spring Formation (Anza-Borrego, California, ~2Ma).<ref name=":23">{{Cite journal |last=Murray |first=Lyndon Keith |date=December 2008 |title=Effects of taxonomic and locality inaccuracies on biostratigraphy and biochronology of the Hueso and Tapiado formations in the Vallecito Creek-Fish Creek section, Anza-Borrego Desert, California (Masters thesis) |url=http://hdl.handle.net/2152/15340 |journal=University of Texas at Austin Libraries}}</ref> Correspondingly, ''A. simus'' is most plentiful from western North America,<ref name="Emslie-1985" /><ref name="Martin-1978">{{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="Trayler-2015">{{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|url-access=subscription }}</ref><ref name="Pérez-Crespo-2018">{{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="Harris-1985" /><ref name="Esker-2010" /><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|url-access=subscription }}</ref><ref name=":13" /> Their ranges may have met in the Middle Pleistocene of Kansas,<ref name="Richards-1996" /> with ''A. simus'' migrating east in the Late Pleistocene (around the extinction of ''A. pristinus'').<ref name="Schubert-2010a" /><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 half a million years during the Middle Pleistocene (''A. pristinus'' went extinct about 300,000 BP), no direct evidence of overlap or competition has been found in the fossil record as of yet, as both species established largely separate ranges.<ref name="Schubert-2010a" />
Irvingtonian age (1,900,000-250,000 BP) specimens of ''A. simus'' are particularly sparse. Finds are mostly from California, with additional remains from Kansas, Nebraska, Montana and Texas,<ref name="Scott-1993">{{Cite journal |last1=Scott |first1=Eric |last2=Cox |first2=Shelley M. |date=May 24, 1993 |title=''Arctodus simus'' (Cope, 1879) from Riverside County, California |url=https://ucmp.berkeley.edu/science/paleobios/backissues/v15no2_scott&cox.pdf |journal=PaleoBios |volume=15 |issue=2 |pages=27–36}}</ref><ref name="Hill-2000" /><ref name="Kurtén-1967">{{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> and potentially Irvingtonian trace fossils from Missouri,<ref name="Lucas-2007" /><ref name=":19" /><ref name=":22" /><ref name=":25" /> and Oregon.<ref name=":26" /> However, ''A. simus'' became a pancontinental species in the Rancholabrean faunal stage (Late Pleistocene), sharing that distinction with the American black bear.<ref name="Bell-2004" /><ref name="Esker-2010">{{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 ''A. simus''{{'}} large temporal and geographic range, fossil remains are comparatively rare (109 finds as of 2010, in otherwise well-sampled localities).<ref name="Schubert-2010a" /><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|bibcode=2021CBio...31E2728P |s2cid=233303447 |hdl=10037/22808|hdl-access=free|pmc=7617452}}</ref>
The mitochondrial genome of ''Tremarctos ornatus'' (the modern spectacled bear) is more closely ''Arctotherium'' than ''Arctodus''.<ref name="Mitchell20162">{{cite journal |last1=Mitchell |first1=K. J. |last2=Bray |first2=S. C. |last3=Bover |first3=P. |last4=Soibelzon |first4=L. |last5=Schubert |first5=B. W. |last6=Prevosti |first6=F. |last7=Prieto |first7=A. |last8=Martin |first8=F. |last9=Austin & Alan Cooper |first9=J. J. |year=2016 |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 |doi=10.1098/rsbl.2016.0062 |pmc=4881349 |pmid=27095265 |article-number=20160062}}</ref> However, a preliminary investigation of the nuclear DNA of short faced bears suggests either an extensive history of hybridization between ''Arctodus'' and ''Tremarctos'' in North America, or hybridization between ''Tremarctos'' and ''Arctotherium'' (likely ''A. wingei'') in either Central America or South America.<ref name=":27">{{Cite bioRxiv |biorxiv=10.1101/2021.02.05.429853v2 |first1=Alexander T. |last1=Salis |first2=Graham |last2=Gower |title=Ancient genomes reveal hybridisation between extinct short-faced bears and the extant spectacled bear (''Tremarctos ornatus'') |date=2021-03-10 |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.}} {{S2CID|231885176}}</ref> Regardless, no evidence of hybridization between ''Arctodus'' and ursine bears was found despite an overlap with black bears and brown bears in Pleistocene North America.<ref name=":13" /><ref name=":27" />
==Description== === Size === thumb|left|Restoration of ''A. simus''
==== ''Arctodus pristinus'' ==== Around the size of grizzly bears, ''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="Florida Museum-2017" /> Floridan ''A. pristinus'' individuals were calculated to an average around {{convert|140|kg|abbr=on}}.<ref name="Van Valkenburgh-2016">{{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><ref name="Fowler-2021">{{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 |bibcode=2021MamRv..51..465F |s2cid=233847639}}</ref> The dimensions of some individuals from Port Kennedy Bone Cave and Aguascalientes, though, suggest that northern and western ''A. pristinus'' populations may have been larger than Floridan ''A. pristinus'',<ref name="Richards-1996" /> being up to {{Convert|400|kg|lb|abbr=on}}.<ref name="Soibelzon-2011">{{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 |hdl=11336/104215 |jstor=23019499 |s2cid=129585554 |hdl-access=free}}</ref>
==== ''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=https://www.adfg.alaska.gov/index.cfm?adfg=wildlifenews.view_article&articles_id=232 |access-date=2008-01-12 |publisher=Alaska Fish and Wildlife News}}</ref><ref name="Fisher-2018">{{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|1|abbr=on}}.<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="Richards-1995">{{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="Fisher-2018" /><ref name="Mattson-1998">{{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><ref name="Matheus-2003" /> The average weight of ''A. simus'' was about {{Convert|625|kg|lb|abbr=on}}, with the maximum recorded at {{Convert|957|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 |bibcode=2010JVPal..30..262F |doi=10.1080/02724630903416027 |hdl=10630/33066 |s2cid=85649497 |hdl-access=free}}</ref><ref name="Van Valkenburgh-2016" />
==== Sexual dimorphism ==== [[File:Short Faced Bear FMNH.jpg|thumb|''A. simus'' skeletal at the Field Museum of Natural History, Chicago]] ''Arctodus'' has been described as very sexually dimorphic; ''A. simus'' males were sometimes twice as large as females.<ref name="Schubert-2010b">{{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 |bibcode=2010QuInt.217..188S |doi=10.1016/j.quaint.2009.11.010}}</ref> Akin to its relative, the spectacled bear (with male spectacled bears being 30-40% larger than females), the larger, massive ''Arctodus'' individuals are considered male, particularly older males, with the smaller, more lightly built individuals being females.<ref name="Schubert-2010a" /><ref name="Schubert-2010b" /><ref name="Scott-1993" /> As with ''T. ornatus'', specimens with a large sagittal crest were likely male, whereas females had a reduced or no sagittal crests.<ref name="Emslie-1995" /> A 2025 mitochondrial DNA study affirmed sexual dimorphism in ''A. simus'', with sexually dimorphic size classes and a uniform population being described from at least 31 individuals recovered from 28 sites across the United States and Canada.<ref name=":11">{{Cite journal |last1=Salis |first1=A. T. |last2=Schubert |first2=B. W. |last3=Bray |first3=S. C. E. |last4=Heiniger |first4=H. |last5=Meachen |first5=J. |last6=Cooper |first6=A. |last7=Mitchell |first7=K. J. |year=2025 |title=Genetic diversity, phylogeography, and sexual dimorphism in the extinct giant short-faced bear (''Arctodus simus'') |journal=Zoological Journal of the Linnean Society |volume=203 |issue=2 |at=zlaf001 |doi=10.1093/zoolinnean/zlaf001 }}</ref>
===== <small>Studies</small> ===== In a 2010 study, the mass of six ''A. simus'' specimens was estimated; half of the specimens weighed between {{convert|740|and|957|kg|lb|abbr=on}}, with a mean weight around 850 kg, suggesting larger (male) specimens were probably more common than previously thought. The other (female) specimens were calculated to be less than {{Convert|500|kg|lb|abbr=on}}. The weight range calculated from all examined specimens was between 957 kg and {{Convert|317|kg|lb|abbr=on}}.<ref name="Figueiridio_et_al_20102" /> A 1999 study by Per Christiansen calculated a mean weight of {{Convert|770|kg|lb}} from seven male ''A. simus'' limb bones, suggesting large males weighed between {{Convert|700|and|800|kg|lb|abbr=on}}.<ref name="Christiansen-1999">{{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> Hypothetically, the largest ''A. simus'' males may have approached {{Convert|1000|kg|lb|abbr=on}},<ref name="Christiansen-1999" /><ref name="Voorhies-1986" /> or even {{convert|1200|kg|lb|abbr=on}}.<ref name="Soibelzon-2011" /> However, a 2006 study argued that the maximum size of ''Arctodus'' was roughly {{Convert|555|kg|lb|abbr=on}}, based on the largest known skull.<ref name="Sorkin-2006">{{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 |bibcode=2006HBio...18....1S |doi=10.1080/08912960500476366 |s2cid=85301983}}</ref>
=== 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. ''A. pristinus'' is distinguished from ''A. simus'' by smaller, narrower, and less crowded teeth. The morphologies of both species are otherwise very similar. As a result, differentiating ''A. simus'' from ''A. pristinus'' can be difficult, as male individuals of ''A. pristinus'' can overlap in size with females of ''A. simus''.<ref name="Schubert-2010a" /><ref name="Schubert-2003">{{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="Schubert-2009" /> ''Arctodus simus'' superficially resembled living hyaenids in skull shape and relative lengths of the trunk, back and limbs.<ref name="Sorkin-2006" /> The most nearly complete skeleton of ''A. simus'' found in the United States was unearthed in Fulton County, Indiana; the original bones are in the Field Museum of Natural History, Chicago.<ref name="Richards-1995" /><ref name="Stark-2022" /> Historically, individual specimens of ''A. simus'' from Missouri and Texas have been suggested to represent new species, due to limb and cranial characteristics respectively.<ref name=":20">{{Cite book |last=Mehl |first=M. G. |url=https://share.mo.gov/nr/mgs/MGSData/Books/Educational/Missouri's%20Ice%20Age%20Mammals/ED-001.pdf |title=Missouri's Ice Age Mammals |date=December 1962 |publisher=State of Missouri: Department of Business and Administration |pages=67–68}}</ref><ref name="Seifert, M.-1962" />
==== Skull ==== [[File:Arctodus simus skull (TMP 1988.061.0001), Royal Tyrrell Museum, Drumheller, Alberta, 2025-07-13.jpg|thumb|''A. simus'' skull, Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta]]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, potentially giving ''Arctodus'' a more felid-like appearance.<ref name="Kurtén-1967" /><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 |bibcode=2011PBioS.278.1831G }}</ref> Matheus suggested that a broad snout could have housed a highly developed olfactory apparatus, or accommodated a larger throat passage to bolt down large food items, akin to spotted hyenas.<ref name="Matheus-1995">{{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|url-access=subscription }}</ref> This apparent shortness, though, is an illusion caused by the deep snouts and short nasal bones of tremarctine bears compared with 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 omniherbivorous spectacled bear.<ref name="Emslie-1985">{{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="FIGUEIRIDO-2009">{{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 Hill-Shuler locality, Texas, were noted as being distinctly "short-faced" in comparison with other ''A. simus'' individuals.<ref name="Gillette-1992">{{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="Seifert, M.-1962">{{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 orbits of ''Arctodus'' are proportionally small compared to the size of the skull, and somewhat laterally orientated (a characteristic of tremarctine bears), more so than actively predatory carnivorans or even the brown bear, suggesting that stereoscopic vision was not a priority.<ref name="Sorkin-2006" /><ref name="FIGUEIRIDO-2009" /><ref name="Baryshnikov-1994">{{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 sphenoidal openings crowd together more in ''A. simus'' than in ''Ursus''.<ref name="Steffen-2018" /> Although samples are limited, the middle ear 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 |bibcode=2022JMorp.283.1337D }}</ref> The canalis semicircularis lateral suggests that ''A. pristinus'' had a head posture of 48°, which being more oblique than several ''Arctotherium'' and ''Tremarctos'' species, could also infer a greater capacity for long-distance vision.<ref name=":02">{{Cite journal |last1=Arnaudo |first1=Maria Eugenia |last2=Bona |first2=Paula |last3=Soibelzon |first3=Leopoldo Hector |last4=Schubert |first4=Blaine W. |date=December 2016 |title=Anatomical study of the auditory region of Arctotherium tarijense (Ursidae, Tremarctinae), an extinct short-faced bear from the Pleistocene of South America |journal=Journal of Anatomy |volume=229 |issue=6 |pages=825–837 |doi=10.1111/joa.12525 |issn=0021-8782 |pmc=5108154 |pmid=27460048}}</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="Emslie-1985" /><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 |article-number=e77531 |bibcode=2013PLoSO...877531D |doi=10.1371/journal.pone.0077531 |pmc=3813673 |pmid=24204860 |doi-access=free}}</ref><ref name="Meloro-2011">{{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|url-access=subscription }}</ref> Although the low mandibular condyle relative to the tooth row (and therefore potential wide gape) of ''Arctodus simus'' has been inferred as an adaptation for carnivory,<ref name="Kurtén-1967" /><ref name="Voorhies-1986">{{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 |url=https://liberalarts.tamu.edu/csfa/wp-content/uploads/sites/14/2023/07/CRP-3-1986.pdf |journal=Current Research in the Pleistocene |volume=3 |pages=49–51}}</ref><ref name="Steffen-2018" /> it is also present in the omniherbivorous spectacled bear.<ref name="Figueiridio_et_al_20102" /> Both ''A. pristinus'' and ''T. floridanus'' have condyles raised well above the plane of the teeth, although some ''A. pristinus'' specimens from Florida seem to also possess a low mandibular condyle.<ref name="Sanders-2002">{{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 calvarium and straight cheek bones of ''A. simus'' have been similarly disputed.<ref name="Figueiridio_et_al_20102" /> Michael Voorhies and Richard Corner argue that the jaws of ''A. simus'' are suited to deliver a strong bite at the canines, and calculated the force of the temporalis muscle of ''A. simus'' as being stronger than modern ''Ursus'' and canids, but equivalent to modern lions and ''Panthera atrox''.<ref name="Voorhies-1986" />
A 2009 analysis of the mandibular morphology of tremarctine bears found notable differences between ''A. pristinus'' and ''A. simus'', with ''A. simus'' specimens possessing a concave jaw, large masseter and temporalis muscles, deeper horizontal ramus, and a reduced slicing dentition length when compared to ''A. pristinus''. Instead, ''A. simus'' was most similar to ''Arctotherium angustidens'', but both species of ''Arctodus'' and ''Arctotherium angustidens'' were still comfortably in the "omnivorous" bear craniomorphotype.<ref name="FIGUEIRIDO-2009" />
===== <small>Dentition</small> ===== [[File:Arctodus simus molar.png|left|thumb|165x165px|Right lower second molar (M2) of ''A. simus'', from Rancho La Brea, California]] The premolars and first molars of ''A. pristinus'' are relatively smaller and more widely spaced than those of ''A. simus''.<ref name="Florida Museum-2017" /><ref name="Schubert-2010a" /> As with other tremarctines, the features of the dentition can be quite variable, particularly the M2 molar.<ref name="Emslie-1995" /> Dentition can be a poor indicator of size in ''A. simus'', as some medium-sized individuals have teeth that surpass the size of those with the largest skeletons. Additionally, while ''A. simus'' evolved from the smaller ''A. pristinus'', their teeth remained generally the same size.<ref name="Richards-1996" />
An analysis of the Hunter-Schreger bands 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, agriotheriin bears, and ''Hemicyon''.<ref name="Stefen-2001">{{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 canines, and the high-crowned lower first molar creating a possible carnassial shear with the upper fourth premolar.<ref name="Kurtén-1967" /> Additionally, old individuals of ''A. simus'' exhibit heavy wear of the first molar and upper fourth premolar.<ref name="Sorkin-2006" /> However, the wearing of the molars to a relatively flat and blunt loph (suitable as a crushing platform as per modern omnivorous bears), small shear facet, and the flattened cusps across age ranges (unlike carnivores, which instead have carnassial shears) disagree with this hypothesis.<ref name="Emslie-1985" /><ref name="Figueirido-2008">{{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|url-access=subscription }}</ref><ref name="Steffen-2018" /> The purpose of the low relative grinding area of the molars has been questioned.<ref name="Sorkin-2006" />
==== Postcranial ==== ===== <small>Limbs</small> ===== 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'' were not 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 to the necessary ratio between body length and body mass of the huge bear.<ref name="Figueiridio_et_al_20102" /><ref name="Matheus-1997" /> Other researchers, however, argue that the limb bones of ''A. 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 big cats. Rather than for running, these elongated limb bones may have evolved for increased locomotor efficiency during prolonged travel.<ref name="Matheus-2003">{{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><ref name="Jiangzuo-2023">{{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> This stiff-legged, swinging gait could have been similar to that of a polar bear.<ref name="Churcher-2011" /> The forelimb morphology of ''A. simus'' has been argued to represent the early stages of cursorial evolution,<ref name="Lynch-2012">{{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> however the lack of distally elongated limbs and elbow morphology discredits this.<ref name=":0">{{Cite journal |last1=Samuels |first1=Joshua X. |last2=Meachen |first2=Julie A. |last3=Sakai |first3=Stacey A. |date=13 September 2012 |title=Postcranial morphology and the locomotor habits of living and extinct carnivorans |url=https://onlinelibrary.wiley.com/doi/10.1002/jmor.20077 |journal=Journal of Morphology |language=en |volume=274 |issue=2 |pages=121–146 |doi=10.1002/jmor.20077 |issn=0362-2525 |pmid=22972188 |url-access=subscription}}</ref><ref name="Jiangzuo-2023" /> Additional theories 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="Emslie-1985" /><ref name="Mattson-1998" />
Most researchers believe that ''A. simus'' had well developed medial humeral epicondyles, facilitating powerful forelimbs,<ref name="Jiangzuo-2023" /><ref name=":0" /> although this has been disputed.<ref name="Sorkin-2006" /> The relatively broad humeral and femoral epicondyles (being characteristic of polar bears and diggers) supports the idea of powerful forearms capable of subduing large prey, while also suggesting ''A. simus'' could have foraged for roots, tubers, and ground squirrels.<ref name=":0" /> ''A. simus'' has also been argued to possess higher degree of forelimb dexterity,<ref name="Emslie-1985" /><ref name="Meloro 133–146" /> due shape of the elbow joint,<ref name="Meloro 133–146" /> along with a well-developed medial epicondyle (forming an angle with the condyle), and a shallower olecranon fossa supporting a wide range of ulna rotation.<ref name="Jiangzuo-2023" /> While terrestrial, this ancestral trait for arboreality was retained in ''Arctodus'' (along with ''Arctotherium'' and the giant panda) to either assist in foraging for vegetation,<ref name="Emslie-1985" /><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> subdue prey,<ref name="Jiangzuo-2023" /> or scavenge carcasses.<ref name="Mitchell-2016">{{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 |article-number=20160062 |doi=10.1098/rsbl.2016.0062 |pmc=4881349 |pmid=27095265}}</ref>
===== <small>Paws</small> ===== The paws (metapodials and phalanges) of ''Arctodus'' were characteristically long, slender, and more elongated along the third and fourth digits compared to 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 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="Matheus-1997">{{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="Mattson-1998" />{{multiple image | align = right | direction = vertical | total_width = 185 | image1 = Arctodus White Sands Pawprint.png | alt1 = | alt2 = | footer = The footprint of ''A. simus'' (White Sands, New Mexico) }}
This is potentially contradicted, though, by possible ''A. simus'' trackways from near Lakeview, Oregon, with strong toe splaying, three centrally aligned and 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 hindfoot overstep the forefoot when walking, like modern bears.<ref name=":26">{{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.oregon.gov/dogami/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 name=":3">{{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 ''A. simus'' at Riverbluff Cave (as they were 4 m above the floor of the cave) were nearly 20 cm in width.<ref name="Lucas-2007">{{Cite journal |last1=Forir |first1=Matthew |last2=Ciampaglio |first2=Chuck |last3=Ryan |first3=Nicole |date=2007 |editor-last=Lucas |editor-first=Spencer G. |editor2-last=Spielmann |editor2-first=Justin A. |editor3-last=Lockley |editor3-first=Martin G. |title=Preliminary Investigation of the Trackways and Claw-Marks Within the Riverbluff Cave System, Springfield, Missouri |url=https://books.google.com/books?id=bGbmCQAAQBAJ&dq=riverbluff+cave+arctodus&pg=PA3 |journal=New Mexico Museum of Natural History and Science |language=en |volume=Cenozoic Vertebrate Tracks and Traces |issue=Bulletin 42}}</ref><ref name=":19">{{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><ref>{{Cite journal |last1=Hunt |first1=Adrian P. |last2=Lucas |first2=Spencer G. |date=2007 |editor-last=Lucas |editor2-last=Spielmann |editor3-last=Lockley |title=Cenozoic vertebrate trace fossils of North America: Ichnofaunas, ichnofacies and biochronology |url=https://www.researchgate.net/publication/281823202 |journal=New Mexico Museum of Natural History |volume=Bulletin 42 |page=25}}</ref>
The presence of a partial false thumb in ''A. simus'' is a characteristic shared with ''T. floridanus'' and the spectacled bear, and is possibly an ancestral trait. Absent in the Ursinae, the false thumb of the spectacled bear has been suggested to assist in herbivorous food manipulation (such as bromeliads, leaves, berries, tree bark and fruits, cactus fruits and pulp, palm hearts and fronds) or arboreality.<ref name="Salesa-2006">{{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="Emslie-1985" />
==== Paleopathology ==== Beyond carbohydrate-associated dental pathologies present in the genus,<ref name="Schubert-2003" /><ref name="Figueirido-2017">{{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="Steffen-2018" /> extensive pathologies have been preserved on the most nearly complete skeleton of ''Arctodus''. The leading hypothesis suggests the Fulton County ''Arctodus'' specimen suffered from a syphilis-like (treponemal) disease, or yaws, based on the various lesions present.<ref name="Richards-1995" /><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="Sorkin-2006" /> with abscesses noted between the molars and on both ulnae. Hypotheses include syphilis, osteoarthritis, a fungal infection in addition to long-term syphilis, or an infected wound.<ref name="Richards-1995" /><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, Alaska, also exhibit either pathological growths or periodontal disease,<ref name="Richards-1996" /> along with a healed toe bone from Big Bear Cave, Missouri.<ref name="Stark-2022" />
== Paleobiology ==
=== Locomotion === Paul Matheus proposed that ''A. simus'' may have moved in a highly efficient, moderate-speed 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 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="Matheus-2003" /> His calculations suggested that ''Arctodus'' likely had a top speed of {{Convert|40-45|km/h|mph|abbr=on}}, and based on hyaenid proportions, would shift from single-foot 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 at {{Convert|10|km/h|mph|abbr=on}}.<ref name="Matheus-2003" /> This mobility would have facilitated travelling across a large home range, which <!-- David J. Mattson suggests --> may have topped {{Convert|1000|sqmi|km2|abbr=on}}.<ref name="Stark-2022" /> Swimming has also been presented as a hypothesis for the colonization of Vancouver Island by ''Arctodus simus''.<ref name="Steffen-2010" /><ref name="Stark-2022" />
=== Maturity === Examinations on a mostly full-sized (likely 4 to 6-year-old female) individual of ''A. simus'' from an Ozark cave suggest that ''Arctodus'', like other ursids, reached sexual maturity well before full maturity. Fused sutures, epiphyses, and epiphyseal plates, well developed premassateric fossa, along with tooth eruption and tooth wear, have been used to determine adulthood in ''Arctodus.''<ref name="Emslie-1995" /><ref name="Schubert-2003" /><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: 8px ''A. simus'' described by Salis et al. (2025)
8px Chiquihuite Cave ''A. simus'' 8px Unassigned ''A. simus''|places={{location map~ |North America| label = Chiquihuite Cave (11,419 ± 34 BP) | position = none | lat= 24.609470 | long= -101.188001 | mark= Orange 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= Steel pog.svg}}
{{location map~ |North America| label = Sheriden Cave (11,566 ± 40 BP) | position = none | lat=40.980733 | long=-83.444783| mark= DeepPink pog.svg}} {{location map~ |North America| label = Saltville Valley (14,853 ± 55 BP) | position = none | lat=36.873611 |long=-81.760833|mark= DeepPink pog.svg}} {{location map~ |North America| label = Natural Trap Cave (20,220 ± 150 BP) | position = none | lat=44.973333 | long= -108.193056 | mark= DeepPink pog.svg}} {{location map~ |North America| label = Oso Cave | position = none | lat= 32.120244 | long= -104.581977 | mark= DeepPink pog.svg}} {{location map~ |North America| label = Bonner Springs (Kaw / Kansas River, 10,921 ± 50 BP) | position = none | lat=39.059722 | long=-94.883611 | mark= DeepPink pog.svg}}
{{location map~ |North America| label = Clover Bar (Edmonton)| position = none | lat=53.596164 | long= -113.354075 | mark= DeepPink pog.svg}} {{location map~ |North America| label = Gold Run Creek (26,040 ± 270 BP) | position = none | lat=63.698261 |long=-138.609632 | mark= DeepPink pog.svg}} {{location map~ |North America| label = Cripple Creek | position = none | lat=62.766667 |long=-137.383333 |mark= DeepPink pog.svg}}
{{location map~ |North America| label = Sixtymile River | position = none | lat= 63.554796 | long= -139.825129 | mark= DeepPink pog.svg}}
{{location map~ |North America| label = Dawson (Dawson City, Eldorado Creek, Gold Run, Hester Creek, Lower Hunker Creek, Ophir Creek, Quartz Creek) | position = none | lat=63.97 |long=-139.1 |mark= DeepPink pog.svg}}
{{location map~ |North America| label = Fairbanks (Ester Creek, Eva Creek Mine, Goldstream) | position = none | lat= 64.846267 | long= -147.734202 | mark= DeepPink pog.svg}}
{{location map~ |North America| label = Old Crow Flats | position = none | lat=67.441 |long=-139.82|mark= DeepPink pog.svg}}}}Several mitochondrial DNA studies suggest ''Arctodus simus'' had a notably low level of genetic diversity, comparable with solitary & wide-ranging carnivorans such lynx and puma, or species with recent bottlenecks.<ref name=":11" /><ref name="Bray-2010" /> A landmark 2025 study demonstrated that ''A. simus'' lived in a single interconnected population and was wide-ranging, which may be linked with its morphological adaptations towards long-distance travel. ''A. simus'' lacked mitochondrial endemism, and like other fauna endemic to the pre-Pleistocene Americas, ''A. simus'' maintained genetic connectivity between its eastern Beringian population and populations south of the ice sheets until the isolation of Beringia during the Last Glacial Maximum, with four distinct lineages across five haplotypes intermingled with eastern Beringian specimens. The last common ancestor between Beringian and southern populations was 31,500 BP.<ref name=":11" /> While suggested by Kurtén in the past, there is no evidence for subspecies in ''A. simus'', such as distinctive genetic diversity or phylogeographic structure. The last common ancestor between all specimens from the 2025 study was the Middle Pleistocene (209,100 BP); however, all specimens which postdate 100,000 BP have a last common ancestor was in the Late Pleistocene (73,600 BP).<ref name=":11" /> However, this does not entirely preclude genetic diversity in ''Arctodus simus'', with genetic samples from Chiquihuite Cave, Zacatecas possibly indicating a deep divergence with other specimens of ''A. simus''.<ref name="Pedersen 2728–2736.e8" /> A sample from the Channel islands has been studied but its relatedness is unknown.<ref name="Mychajliw-20202">{{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>
A 2020 analysis of the genetic history of three ''A. simus'' individuals from the Yukon suggests an extended history of small effective population size. A steady decline of the breeding population around 1 Mya (from about 16,500 individuals to 4,000 individuals) was halted by a slight increase in numbers 60,000 BP (7,500 individuals). This was followed by a decrease around 48,000 BP (correlated with expanding Yukon forests ''circa'' the MIS 3 interstadial), which continued until the local extinction of Beringian ''A. simus'' by near 23,000 BP during the last glacial maximum.<ref name=":13" />
== Hibernation == [[File:Fall_in_the_Ozarks.jpg|thumb|231x231px|''A. simus'' specimens have been particularly plentiful from caves in the montane woodlands of the US Interior Highlands, such as the Ozarks.|left]] ''Arctodus pristinus'' specimens have been found in caves such as Port Kennedy (Pennsylvania, where fossils from as many as 36 individuals have been found), Cumberland Cave (Maryland) and Hamilton Cave (West Virginia), often in association with the black bear. This suggests a close association with the biome.<ref name="Emslie-1995" /><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><ref name=":7" />
According to a 2003 study, in karst regions, fossils of ''A. simus'' have been recovered almost exclusively from cave sites.<ref name="Schubert-2003" /> In the contiguous United States, that about 38% of all sites are from caves (possibly 50% in western USA)<ref name="Lucas">{{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> suggests a close association between this species and cave environments. Metabolic denning (hibernation/torpor) is unclear in ''Arctodus''. Like polar bears, males and unmated females of ''A. simus'' may have forgone denning, leaving maternal denning by females as the preferred explanation behind the recovery of the small, yet relatively complete individuals recovered from caves.<ref name="Schubert-2003" /><ref name="Fowler-2021" /><ref name=":11" /> No physical remains of adults with associated offspring are currently known,<ref name="Schubert-2010b" /> however trace fossils of co-denning have been reported from Riverbluff Cave.<ref>{{Cite AV media |url=https://www.youtube.com/watch?v=haaxRbBMQis |title=Learn More About Riverbluff Cave, The Oldest Ice Age Fossil Cave In North America Near Springfield |date=2022-05-27 |last=Kansas City Star |access-date=2025-11-26 |via=YouTube}}</ref> Regardless, ''Arctotherium angustidens'', a fellow giant short-faced bear, has been recovered with offspring from a cave in Argentina.<ref>{{Cite journal |last1=Soibelzon |first1=Leopoldo H. |last2=Pomi |first2=Lucas H. |last3=Tonni |first3=Eduardo P. |last4=Rodriguez |first4=Sergio |last5=Dondas |first5=Alejandro |date=2009-09-01 |title=First report of a South American short-faced bears' den (Arctotherium angustidens): palaeobiological and palaeoecological implications |url=http://sedici.unlp.edu.ar/handle/10915/5364 |journal=Alcheringa: An Australasian Journal of Palaeontology |volume=33 |issue=3 |pages=211–222 |bibcode=2009Alch...33..211S |doi=10.1080/03115510902844418 |issn=0311-5518 |s2cid=55636895 |url-access=subscription}}</ref>
At Riverbluff Cave, the most abundant claw marks are from ''A. simus''. They are most abundant at the bear beds and their associated passageways, indicating a close relationship with denning.<ref name="Lucas-2007" /> Numerous "bear" beds often preserve ''A. simus'' and both Pleistocene and modern American black bears in association (''U.a. amplidens'' and ''U. a. americanus'')- such deposits have been found in Missouri,<ref name="Schubert-2003" /><ref name=":17" /> Oklahoma,<ref name=":1">{{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 name=":2">{{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> and Potter Creek Cave, California.<ref name="Feranec-2009" /> These mixed deposits are assumed to have accumulated over time, as individual bears (including ''Arctodus'') died during winter sleep.<ref name=":17" /> Furthermore, environmental DNA suggests that ''Arctodus'' and black bears shared a cave in Chiquihuite Cave, Zacatecas.<ref name="Pedersen 2728–2736.e8" /> At Labor-of-Love Cave (Nevada) both American black bears and brown bears have been found in association with ''A. simus''. A 1985 study noted that sympatry between ''Arctodus'' and brown bears preserved in caves is rare, with only Little Box Elder Cave (Wyoming) and Fairbanks II (Alaska) hosting similar remains.<ref name="Emslie-1985" /><ref name="Kurten-1974">{{Cite journal |last1=Kurtén |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>
== Diet == Scholars today mostly conclude that ''A. 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="FIGUEIRIDO-2009" /><ref name="Steffen-2018" /><ref name="Mychajliw-20202"/><ref name="Van Valkenburgh-2016" /> If ''A. simus'' wasn't largely herbivorous,<ref name="Emslie-1995" /><ref name="Emslie-1985" /> 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="Sorkin-2006" /><ref name="Steffen-2018" /><ref name="Domínguez-Rodrigo-2022">{{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 |page=6045 |bibcode=2022NatSR..12.6045D |doi=10.1038/s41598-022-09480-7 |issn=2045-2322 |pmc=9061710 |pmid=35501323 |doi-access=free}}</ref>
=== Herbivory === [[File:Juniperus_communis_fruits_-_Keila.jpg|thumb|231x231px|''Arctodus'' faeces found at South Dakota and the Yukon contain ''Juniperus'' seeds. Seed cones and 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="Figueirido-2008" /><ref name="Jones-2016">{{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 |bibcode=2016AcPaP..61..735J }}</ref> Morphologically, ''A. simus'' exhibits masticular and dental characteristics that confirm that short-faced bears such as the spectacled bear and ''Arctodus'' were adapted to and actively consumed vegetation.<ref name="Emslie-1985" /><ref name="FIGUEIRIDO-2009" /><ref name="Donohue2" /><ref name="Figueirido-2008" /><ref name="Meloro-2011" /> This is affirmed by a lack of dental damage associated with carnivory amongst specimens of ''Arctodus''.<ref name="DeSantis-2015">{{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 that have been found, such as incisor wear and supragingival dental calculi in a young individual from Missouri,<ref name="Schubert-2003" /> and cavities associated with carbohydrate consumption in individuals from the La Brea Tar Pits and Pellucidar Cave (Vancouver Island), further suggest an omnivorous diet for ''A. simus''.<ref name="Figueirido-2017" /><ref name="DeSantis-2015" /><ref name="Steffen-2018" /> Additional morphological adaptations include dexterous forelimbs and a partial false thumb, which would have assisted in foraging for vegetation,<ref name="Meloro 133–146" /><ref name="Salesa-2006" /> along with the body size of large ''A. simus'' (about 1000 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="Emslie-1985" /><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 |article-number=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|url-access=subscription }}</ref>
While features of ''A. simus''<nowiki/>' morphology suggest herbivory, their close phylogenetic relationship to the omniherbivorous 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'', while evidence of digging adaptations in ''Arctodus''<nowiki/>' forelimbs and claws (e.g. for rooting) is mixed.<ref name="Mattson-1998" /><ref name="Sorkin-2006" /><ref name=":0" /> Regardless, gross tooth wear suggests consumption of plant matter in the diet of ''A. simus''.<ref name="Donohue2" /><ref name="Emslie-1985" /> The diet of individuals from La Brea was most similar to the spectacled bear, which consumes tough leafy matter, seeded and pitted fruits, and occasional animal flesh. ''Arctodus''<nowiki/>' tooth wear remained consistent throughout the Pleistocene in La Brea. This indicated a less generalized diet than modern omniherbivorous 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 ''Ursus speleaus'' suggest dietary differences between the species, with cave bears consuming tougher vegetation than ''A. simus''.<ref name="Jones-2016" /> Although some researchers argue that herbivory should be more obvious from the isotope data gathered from northern ''A''. ''simus'',<ref name="Schubert-2009" /> several ''A''. ''simus'' coprolites from The Mammoth Site in South Dakota and Meander Cave at Ni'iinlii'njik Territorial Park, Yukon contain ''Juniperus'' seeds (toxic to black and brown bears).<ref name="Baryshnikov-1994" /><ref name=":16">{{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>
=== Predatory behavior === [[File:SpectacledBear1 CincinnatiZoo.jpg|thumb|''Arctodus''<nowiki/>' closest living relative is the spectacled bear. Although mostly herbivorous, ''Tremarctos ornatus'' is occasionally 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 C<sub>3</sub> resources) 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 megaherbivores, and hindered the chasing down of nimbler prey.<ref name="Matheus-2003" /><ref name="Lynch-2012" /> Nevertheless, larger ''A. simus'' males 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="Kubiak-2022">{{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 |url-access=subscription}}</ref> Furthermore, the much larger frame of ''A. simus'' would have provided an advantage in disputes over carcasses.<ref name="Schubert-2010a" />
Studies establish that ''A. 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="Figueirido-2017" /><ref name="Kubiak-2022" /><ref name="Bocherens-2015">{{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 |url-access=subscription}}</ref><ref name="Mychajliw-20202"/> The extinction of cursorial, hypercarnivorous ''Borophagus'' and ''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="Mitchell-2016" /><ref name="Jiangzuo-2023" />
==== Bone damage ==== [[File:American_mastodon_with_calf.jpg|thumb|''Arctodus'' may have found young proboscideans to be suitable prey.|left]]The bite marks found on many bones of ground sloths (''Northrotheriops texanus'') and young proboscideans at Leisey Shell Pit in Florida matched the size of the canine teeth of ''A. pristinus''. Whether these bite marks are the result of active predation or scavenging is unknown.<ref name="Florida Museum-2017" /> Additionally, ''A. 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|url-access=subscription }}</ref>
''Arctodus simus'' has been found in association with proboscidean remains near Frankstown, Pennsylvania, (juvenile mastodon),<ref name="Science-2010">{{Cite web |date=2010-02-17 |title=A Baby Mastodon Deathtrap (?) |url=https://www.nationalgeographic.com/science/article/a-baby-mastodon-deathtrap |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> and near Huntington Reservoir, Utah and the Mammoth Site, South Dakota (Columbian mammoths).<ref name="Baryshnikov-1994" /><ref name="Gillette-1992" /> Additionally, a mammoth rib from the Mammoth Site has a canine puncture likely caused by ''A. simus'',<ref>{{Cite journal |last1=Wilkins |first1=William |last2=Pagnac |first2=Darrin |last3=Ellingsen |first3=Marius |date=31 October 2013 |title=Chewing the Fat with Arctodus: Collaborative Undergraduate Development of a Calibrate Apparatus for Use in Bite Force Research |url=https://vertpaleo.org/wp-content/uploads/2021/03/SVP-2013-merged-book-10-15-2013.pdf |journal=Journal of Vertebrate Paleontology |volume=73rd Meeting |page=238}}</ref> with several Columbian mammoth bones from Huntington Reservoir also recording ursid gnaw marks attributed to ''A. simus''.<ref name="Gillette-1992" /> A woolly mammoth specimen from Saltville, Virginia was likely scavenged on by ''A. simus'', as evidenced by a canine gouge through the calcaneus.<ref name="Schubert-2009" />
While the canines of ''Panthera atrox'' overlap in size with ''A. simus,'' complicating the identification of tooth marks,<ref name="Schubert-2009" /> damaged bones from near Tanana River, Alaska, suggest that ''A. simus'' transported megafaunal long bones 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>{{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|bibcode=1997Gearc..12..657S }}</ref> at a time when lions had a limited overlap with ''A. simus'' in Beringia.<ref name="Salis-2020">{{cite journal |biorxiv=10.1101/2020.09.03.279117 |first1=Alexander T |last1=Salis |first2=Sarah C E |last2=Bray |last3=Lee |first3=Michael S Y |last4=Heiniger |first4=Holly |last5=Barnett |first5=Ross |last6=Burns |first6=James A |last7=Doronichev |first7=Vladimir |last8=Fedje |first8=Daryl |last9=Golovanova |first9=Liubov |last10=Harington |first10=C Richard |last11=Hockett |first11=Bryan |last12=Kosintsev |first12=Pavel |last13=Lai |first13=Xulong |last14=Mackie |first14=Quentin |last15=Vasiliev |first15=Sergei |last16=Weinstock |first16=Jacobo |last17=Yamaguchi |first17=Nobuyuki |last18=Meachen |first18=Julie |last19=Cooper |first19=Alan |last20=Mitchell |first20=Kieren J |title=Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge |journal=Molecular Ecology |date=2022 |volume=31 |issue=24 |pages=6407–6421 |doi=10.1111/mec.16267 }}</ref><ref name="Figueirido-2017" /> Spiral fractures on ungulate long bones from Red Willow, Nebraska may have also been caused by ''A. simus''.<ref name="Voorhies-1986" /> Furthermore, a perforated peccary ilium from Sheriden Cave,<ref name="Redmond-2005" /> and peccary remains from Riverbluff Cave may also have been modified by ''A. simus''.<ref name=":22">{{Cite AV media |url=https://www.youtube.com/watch?v=3WbUq6jCW7o |title=River Bluff Cave part 2 |date=2025-04-24 |last=Ozarks First |access-date=2025-11-26 |via=YouTube}}</ref> Bone damage on a cranial fragment (and possibly the humerus) of an ''Arctodus'' individual on Vancouver Island may have been due to cannibalism.<ref name="Steffen-2018" /><ref name="Kubiak-2022" />
=== Isotope analysis ===
==== Carbon-13 ==== Carbon-13 levels in ''Arctodus simus'' (enriched by both plants and prey matter) consistently reflect a diet based on C<sub>3</sub> resources, as analyzed from specimens from Alaska,<ref name="Bocherens-2015" /><ref name="hb">{{Cite journal |last1=Bocherens |first1=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://www.academia.edu/751564 |journal=Comptes rendus de l'Académie des Sciences |volume=320 |issue=8 |pages=779–784 |issn=1251-8050 |language=en}}</ref> California,<ref name="Trayler-2015" /><ref name="Mychajliw-20202"/>''<ref name="Trayler-2012">{{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>'' San Luis Potosí,<ref name="Pérez-Crespo-2018" /> Texas,<ref name="Smith-2022">{{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 |bibcode=2022PNAS..11915015S |doi=10.1073/pnas.2115015119 |issn=0027-8424 |pmc=9522422 |pmid=36122233 |doi-access=free |article-number=e2115015119}}</ref> Vancouver Island,<ref name="Steffen-2010" /><ref name="Kubiak-2022" /> Wyoming,<ref name=":14">{{Cite journal |last1=Chatters |first1=James C. |last2=Potter |first2=Ben A. |last3=Fiedel |first3=Stuart J. |last4=Morrow |first4=Juliet E. |last5=Jass |first5=Christopher N. |last6=Wooller |first6=Matthew J. |date=2024-12-04 |title=Mammoth featured heavily in Western Clovis diet |journal=Science Advances |volume=10 |issue=49 |bibcode=2024SciA...10R3814C |doi=10.1126/sciadv.adr3814 |pmc=11616702 |pmid=39630905 |article-number=eadr3814}}</ref> and the Yukon.<ref name="Fox-Dobbs-2008" /> C<sub>3</sub> resources are typically found in closed to mixed habitats with at least some tree cover (such as open woodlands). This includes C<sub>3</sub> vegetation (leaves, stems, fruits, bark, and flowers from trees, shrubs, and cool season grasses)<ref name="Emslie-1985" /> and the browsers that fed on them, such as deer, camelids, tapir, bison, peccaries and ground sloths.<ref name="Trayler-2015" /><ref name="Pérez-Crespo-2018" /><ref name="Figueiridio_et_al_20102" />''<ref name="Fox-Dobbs-2008" />''
{{location map+|North America|relief=yes|width=250|float=right|caption=Isotope sample map of ''Arctodus simus'' {{small|(hover over dots for more information)}}<br /> Legend: 8px δ13C 8px δ15N 8px Both δ13C & δ15N|places={{location map~ |North America| label = Cedral (−11.8) | position = none | lat=23.816667 |long=-100.716667|mark= Green pog.svg}} {{location map~ |North America| label = Fairmead Landfill (−11.9)| position = none | lat=37.061631 | long= -120.194195 | mark= Green pog.svg}} {{location map~ |North America| label = Irvington (−14.5) | position = none | lat=37.527222 | long= -121.946111 | mark= Green pog.svg}} {{location map~ |North America| label = McKittrick Tar Seeps (-10.9) | position = none | lat=35.296314 |long=-119.626014 |mark= Green pog.svg}} {{location map~ |North America| label = Little Box Elder Cave (-14.9) | position = none | lat= 42.7833 | long= -105.683 | mark= Green pog.svg}}
{{location map~ |North America| label = La Brea Tar Pits (N/A) | position = none | lat=34.0628 |long=-118.356|mark= Red pog.svg|8px}}
{{location map~ |North America| label = San Miguel Island (-17.9, 13.2) | position = none | lat=34.033333 |long=-120.383333|mark= Red-green pog.svg}} {{location map~ |North America| label = Cowichan Head (-18.9, 10.6) | position = none | lat= 48.555260 | long= -123.363879 | mark= Red-green pog.svg}} {{location map~ |North America| label = Friesenhahn Cave (-16.5, 9.7) | position = none | lat=29.682853 | long=-98.477758 | mark= Red-green pog.svg}} {{location map~ |North America| label = Natural Trap Cave (-19, 8.1) | position = none | lat=44.973333 | long= -108.193056 | mark= Red-green pog.svg}} {{location map~ |North America| label = Pellucidar Cave (-19.0, 5.3) (-19.0, 5.5) | position = none | lat=50.400278 | long=-126.975833| mark= Red-green pog.svg}} {{location map~ |North America| label = Fairbanks (-18.0, 8.4) | position = none | lat= 64.846267 | long= -147.734202 | mark= Red-green pog.svg}} {{location map~ |North America| label = Dawson (-18.5, 9.9) | position = none | lat=63.97 |long=-139.1 |mark= Red-green pog.svg}}}}
However, studies are complicated by a lack of compound-specific data,<ref name="Mychajliw-20202"/> with isotope data being variable in carbon-13.<ref>{{Cite journal |last1=Rawlence |first1=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 |bibcode=2016QSRv..142..173R |doi=10.1016/j.quascirev.2016.05.017 |issn=0277-3791 |url-access=subscription}}</ref><ref name="Kohn-2012">{{Cite journal |last1=Kohn |first1=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 |bibcode=2012PPP...326...42K |doi=10.1016/j.palaeo.2012.01.037 |issn=0031-0182 |url-access=subscription}}</ref> For example, while the specimen from Cedral, San Luis Potosí had the strongest δ<sup>13</sup>C value of its local fauna,''<ref name="Pérez-Crespo-2018" />'' specimens analyzed in a 2012 study from Wyoming (Little Box Elder Cave, Natural Trap Cave) had the lowest δ<sup>13</sup>C of the studied fauna, with only ''Ursus'' from Little Box Elder Cave being lower. The authors suggest that seasonality & individual choices within omnivorous diets could result in extreme isotope data in certain teeth.<ref name="Kohn-2012" />
==== Nitrogen-15 ==== Broadly elevated nitrogen-15 levels in ''A. simus'' suggest that ''A. simus'' occupied a relatively high trophic level.''<ref name=":12" /><ref name="Mychajliw-20202"/><ref name=":14" /><ref name="Steffen-2010" /><ref name="Smith-2022" /><ref name="Fox-Dobbs-2008" /><ref name="Bocherens-2015" />'' Data can be variable across individuals and localities; while samples from Rancho La Brea were on a spectrum, some specimens were on the same trophic level as ''Smilodon fatalis''.''<ref name=":12" />'' Specimens from northern Vancouver Island had distinctly lower nitrogen-15 levels, however this may be due to competition between female ''A. simus'' and brown bears.<ref name="Kubiak-2022" /> While samples from Alaska,<ref name="Matheus-1995" />''<ref name="Fox-Dobbs-2008" />''<ref name="hb" /> Texas,''<ref name="Smith-2022" />'' and Vancouver Island were of terrestrial origin,''<ref name="Steffen-2010" />''<ref name="Kubiak-2022" /> samples from coastal California suggested a ~19% consumption rate of seals (along with bison and camels). This partial reliance on marine resources has been suggested to be as a result of a competitive carnivore guild on mainland California.<ref name="Mychajliw-20202"/>
Although elevated nitrogen-15 levels have been argued to indicate pure carnivory, even the isotope data of the most carnivorous Beringian ''Arctodus'' overlapped with modern, typically omniherbivorous brown bears from Europe, central Montana, and eastern Wyoming, demonstrating that isotope data cannot distinguish between hypercarnivores and omnivores that eat a significant amount of animal matter.<ref name="Sorkin-2006" /><ref name="Bocherens-2015" /> Studies are also complicated by a lack of compound-specific data.<ref name="Mychajliw-20202"/> The variability of ''δ''<sup>15</sup>N, such as the extremely high levels from Natural Trap Cave (Wyoming) and Dawson (Yukon) have been suggested by authors to be influenced by the isotopic composition of the local environment and prey (such as muskox),<ref name="Matheus-1995" /><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><ref name="Bocherens-2015" /> individual/evolving prey and plant choices,<ref name="Fox-Dobbs-2008" /> the regionalization and flexibility of ''A. simus''<nowiki/>' diet,<ref name=":14" /> and nutritional stress.<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|url-access=subscription }}</ref>
== 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.]]Endemic to the late Blancan faunal stage and Irvingtonian faunal stage, ''Arctodus pristinus'' was a relatively large tremarctine bear.<ref name="Florida Museum-2017" /> 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="Emslie-1995" /> Kansas, Maryland,<ref name="Richards-1996" /> Nebraska,<ref>{{cite web |title=USNM V 147 |url=https://collections.nmnh.si.edu/search/paleo/?ark=ark:/65665/33655067d-db47-436e-ab91-92fcd6acd6a1 |access-date=2025-12-06 |website=collections.nmnh.si.edu}} Click on image to view the reclassification.</ref> 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 |page=207}}</ref> Pennsylvania,<ref name="Lucas" />'''<ref name="researchgate.net" />''' South Carolina,<ref name="Albright-2020">{{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="Richards-1996" /><ref name=":7">{{Cite book |last1=Eshelman |first1=Ralph E. |url=https://smithsonian.figshare.com/articles/book/Middle_Pleistocene_Cumberland_Bone_Cave_Local_Fauna_Allegany_County_Maryland_A_Systematic_Revision_and_Paleoecological_Interpretation_of_the_Irvingtonian_Middle_Appalachians_USA/28597193/1 |title=Middle Pleistocene Cumberland Bone Cave Local Fauna, Allegany County, Maryland: A Systematic Revision and Paleoecological Interpretation of the Irvingtonian, Middle Appalachians, USA |last2=Bell |first2=Christopher |last3=Graham |first3=Russel W. |last4=Semken Jr. |first4=Holmes A. |last5=Withnell |first5=Charles B. |last6=Scarpetta |first6=Simon G. |last7=James |first7=Helen F. |last8=Godfrey |first8=Stephen J. |last9=Mead |first9=Jim I. |series=Smithsonian Contributions to Paleobiology |date=2025-04-18 |volume=108 |publisher=Smithsonian Institution Scholarly Press |doi=10.5479/si.28597193 |language=en}}</ref> 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="Richards-1996" /><ref name=":4">{{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="Emslie-1995" /> although ''Arctodus'' has been suggested to be generally more carnivorous than contemporary bears.<ref name="Florida Museum-2017" /><ref name="Kurtén-1967" />
==== Eastern North America ==== ''Arctodus pristinus'' is considered a biochronological indicator for the period between the Late Blancan and late Irvingtonian periods of Pleistocene Florida- more fossils of ''A. pristinus'' are known from Florida (about 150) than anywhere else. ''A. pristinus'' recovered from Florida have intraspecific variation that has probable temporal and geographic origins.<ref name="Emslie-1995" /> Regardless of overall size, some ''A. pristinus'' specimens from Leisley Shell Pit 1A possessed dental dimensions and mandibular characteristics more similar to ''A. simus'' than to other ''A. pristinus''.<ref name="Sanders-2002" /> In the Early Pleistocene of Blancan Florida, the Santa Fe River 1 site (~2.2 Ma), which ''Arctodus pristinus'' inhabited,<ref name="Florida Museum-2017" /><ref name="Emslie-1995" /> was a fairly open grassland environment dotted with karst sinks and springs and dominated by longleaf pine flatwoods. ''Arctodus pristinus'' co-existed with terror birds, sabertooth cats, giant sloths (''Eremotherium'', ''Megalonyx'', ''Paramylodon''), giant armadillos (''Glyptotherium,'' ''Holmesina'', ''Pachyarmatherium''), gomphotheres, hyenas, canids (''Borophagus'', ''Canis lepophagus''), peccaries, llamas, dwarf pronghorns, and three-toed horses. Smaller fauna included condors, rails, ducks, 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 |issue=4 |pages=201–229|doi=10.58782/flmnh.xumx1681 |bibcode=2005BFMNH..45..201G }}</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 = Eight Physiographic Regions of the Continental United States.png | 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'' in the early Irvingtonian faunal stage,<ref name="Richards-1996" /><ref name="Bell-2004" /> ''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" /> 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|url-access=subscription }}</ref><ref name="North American Bear Center-2018">{{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> Matheus argues that unlike other Nearctic carnivorans, ''A. simus'' did not appear to have an ecological equivalent ("super-huge bear") in the Palearctic realm.<ref name="Paul-2001" />
''Arctodus simus'' was initially restricted to the western United States during the Irvingtonian.<ref name="Scott-1993" /><ref name="Hill-2000" /><ref name="Kurtén-1967" /> However, in the Rancholabrean faunal stage, ''A. simus'' expanded its range across the Nearctic realm of North America, inhabiting a variety of climatic conditions and environments.<ref name="Ferrusquía-Villafranca-2010" /><ref name="Schubert-2010a" /><ref name="Emslie-1985" /><ref name="Figueirido-2017" /><ref name="Holliday-2014">{{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 2009 study examining megafaunal extinctions in Northern America noted 12 records (<40,000 BP) of ''Arctodus simus'' from the Intermontane Plateaus, 7 from the Pacific Mountain System, 6 each from the Interior Plains and Interior Highlands, 3 each from the Atlantic Plains and Rocky Mountain System, and 1 from the Appalachian Highlands.<ref name="Faith-2009" /> Huge individuals from Alaska to Florida suggests that the late Rancholabrean may have contained the largest known individuals of ''A. simus''.<ref name="Soibelzon-2011" /><ref name="Schubert-2010b" />
==== North American Cordillera ==== The western United States seems to represent a cradle of evolution for ''Arctodus simus''. The earliest confirmed finds of ''A. simus'' are from California, most famously being from the Irvington type locality, which are at least 780,000 years old.<ref name="Bell-2004" /><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> Other Irvingtonian age remains from the Pacific Mountain System come from California, such as Elsinore,<ref>{{Cite journal |last1=III |first1=Alois F. Pajak |last2=Scott |first2=Eric |last3=Bell |first3=Christopher J. |date=13 September 1996 |title=A review of the biostratigraphy of Pliocene and Pleistocene sediments in the Elsinore Fault Zone, Riverside County, California |url=https://www.academia.edu/download/69346012/A_review_of_the_biostratigraphy_of_Plioc20210910-25423-3lhn5q.pdf |journal=PaleoBios |volume=17 |issue=2–4 |pages=28–49}}</ref><ref>{{Cite web |title=Elsinore Fault Zone |url=https://www.utep.edu/leb/pleistnm/sites/elsinore.htm |access-date=2024-07-22 |website=www.utep.edu}}</ref> 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> and Murrieta,<ref name="Scott-1993" /> with footprints from Oregon.<ref name=":26" /> Older yet disputed remains come from El Casco (1.4Mya),<ref name="Scott-1993" /><ref>{{Cite web |title=San Timoteo Badlands |url=https://www.utep.edu/leb/pleistnm/sites/santimoteo.htm |access-date=2024-07-22 |website=www.utep.edu}}</ref> while potential records from the Intermontane Plateaus of eastern California (Anza-Borrego Desert and Victorville) may be as old as 2Mya.<ref name="Richards-1996" /><ref name=":23" /><ref name=":21">{{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 |issn=0272-4634 |jstor=4523978}}</ref><ref name=":24">{{Cite journal |last=Cassiliano |first=Michael |date=1997-03-01 |title=Taphonomy of mammalian fossils across the Blancan-Irvingtonian boundary: Palm Spring Formation, Anza-Borrego desert of southern California |url=https://www.sciencedirect.com/science/article/pii/S003101829600123X |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=129 |issue=1 |pages=81–108 |bibcode=1997PPP...129...81C |doi=10.1016/S0031-0182(96)00123-X |issn=0031-0182 |url-access=subscription}}</ref><ref>{{Cite journal |date=1997 |title=Abstract of Papers. Fifty-Seventh Annual Meeting, Society of Vertebrate Paleontology |journal=Journal of Vertebrate Paleontology |volume=17 |issue=3 |pages=A1–A93 |issn=0272-4634 |jstor=4523848}}</ref>
Thereafter in the Rancholabrean faunal stage, ''A. simus'' was relatively plentiful in western North America, with over 50% of specimens from the western contiguous United States (<40,000 BP).<ref name="Esker-2010" /><ref name="Figueirido-2017" /> ''Arctodus simus'' was integral to what has been referred to as the ''Camelops'' fauna, or alternatively ''Camelops''/''"Navahoceros"'' fauna, a faunal province centered in western North America. The ''Camelops'' fauna was also characterized by shrub-ox, prairie dogs, dwarf pronghorns, Shasta ground sloths, and American lions. 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="Martin-1978" /><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>
===== ''<small>Western Mountains</small>'' ===== [[File:North Slope Santa Ynez Mtns.jpg|thumb|''Arctodus simus'' inhabited Californian savannas for more than a million years.|left]]In the Pacific Mountain System, despite the shift from C<sub>3</sub> dominated habitats (Fairmead & Irvington) to aridified, mixed C<sub>3</sub>-C<sub>4</sub> grasslands (McKittrick Tar Pits) between the Early and Late Pleistocene of the Central Valley, ''Arctodus simus'' remained consistent with the consumption of C<sub>3</sub> resources, and was the only constant member of the local predator guild (along with dire wolves).<ref name="Trayler-2015" /><ref name="Trayler-2012" /> Although dental wear and cavities from specimens collected from the La Brea Tar Pits suggest ''A. simus'' preferred a herbivorous diet,<ref name="Donohue2" /><ref name="Figueirido-2017" /> nitrogen-15 samples from La Brea varied across ''A. simus'' individuals, with some specimens being in the same trophic level as ''Smilodon fatalis''.<ref name=":12">{{Cite journal |last1=Schubert |first1=Blaine |last2=Cox |first2=Shelley |last3=Coltrain |first3=Joan |date=31 October 2013 |title=The Significance of Rancho La Brea for Interpreting the Paleobiology of Giant Short-Faced Bears |url=https://vertpaleo.org/wp-content/uploads/2021/03/SVP-2013-merged-book-10-15-2013.pdf |journal=Society of Vertebrate Paleontology |volume=73rd Meeting |page=207}}</ref> ''A. simus'' is particularly famous from fossils found in the La Brea Tar Pits, with 33 individuals recovered (the most of any locality).<ref name=":12" /><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>{{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 |bibcode=2009BiLet...5...81C }}</ref> As only one juvenile has been found from La Brea, ''A. simus'' is suggested to have been solitary.<ref name="Domínguez-Rodrigo-2022" /> Many more finds come from across California.<ref name="Richards-1996" /><ref name="Feranec-2009" /><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><ref>{{Cite book |last1=Johnson |first1=Emily |url=https://www.researchgate.net/publication/372310748 |title=Mojave National Preserve Paleontological Resource Inventory (Public Version) |last2=Andeskie |first2=Sofia |last3=Tweet |first3=Justin S. |last4=Santucci |first4=Vincent L. |date=July 2023 |publisher=National Park Service |edition=Natural Resource Report NPS/MOJA/NRR—2023/2541 |page=45}}</ref>
In Vancouver Island,<ref name="Steffen-2018" /><ref name="Steffen-2010">{{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 |url-access=subscription }}</ref> and Washington,<ref name="Steffen-2010" /><ref name=":15" /> the Pacific Mountain System transitioned from semi-arid woodland/scrub to pine parklands,<ref name="Steffen-2018" /><ref name=":15" /> heath, and forest steppe.<ref name="Steffen-2010" /><ref name="Adams, J.M.-2001" /><ref>{{Cite journal |last=Kubiak |first=Cara |date=2024 |title=Late Pleistocene Megafauna of Coastal British Columbia: Palaeoecological Insights through the Application of Compound-Specific Stable Isotope Analyses to Museum Specimens (PhD Thesis) |url=https://summit.sfu.ca/_flysystem/fedora/2025-05/etd23277.pdf |journal=Simon Fraser University |page=13}}</ref> According to an isotope analysis, ''A''. ''simus'' held an intermediate trophic position between brown bears and black bears on Vancouver Island (~14,500 BP). As per brown and 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, meat was preferred. While niche-partitioning on Vancouver Island was possible, both ''A. simus'' and brown bears appear to have preferred more open habitats.<ref name="Kubiak-2022" /><ref name="Steffen-2018" />
Comparatively, the Rocky Mountain System had the fewest number of specimens of ''A. simus'' in western North America.<ref name="Esker-2010" /> However, one of the youngest dated ''A. simus'' is from a cave near Huntington Reservoir, Utah, which sits at an elevation of 2,740m (~9,000 ft). The central and southern Rocky Mountains may have acted as refugia for boreal parkland megafauna from the plateau such as ''A. simus'',<ref name="Gillette-1992" /><ref name="Martin-1978" /> with the Huntington specimen being the only confirmed extinct megafauna dated to the Younger Dryas of the Great Basin.<ref name="Goebel-2011">{{Cite journal |last1=Goebel |first1=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 |bibcode=2011QuInt.242..479G |issn=1040-6182|url-access=subscription }}</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><ref name="Kohn-2012" /><ref name=":14" /> 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|url-access=subscription }}</ref>
===== ''<small>Intermontane Plateaus</small>'' ===== [[File:Paleontological_landscape_painting,_White_Sands_National_Park,_United_States.jpg|thumb|A reconstruction of Rancholabrean New Mexico (White Sands).|left]]The Intermontane Plateaus had the highest number of ''Arctodus simus'' specimens south of the ice sheets.<ref name="Esker-2010" /><ref name="Faith-2009" /> 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="Nelson-1983">{{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> In contrast with other parts of North America, the plateaus received more rainfall during the Late Pleistocene, greatly expanding the range of subalpine parkland, piñon-juniper & ponderosa woodlands, sagebrush grasslands and pluvial lakes where desert exists today.<ref name="Goebel-2011" /><ref name="Adams, J.M.-2001" /><ref name="Lucas" /><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|url-access=subscription }}</ref> ''Arctodus simus'' has been recovered from the mid-Wisconsian U-Bar Cave, New Mexico, alongside Shasta ground sloth, shrub-ox, pronghorns (''Stockoceros'', ''Capromeryx''), ''Camelops'', ''Odocoileus'', horses, ''Lynx'', puma, black bear, mountain goats'','' prairie dogs, and Stock's vampire bat.<ref name="Harris-1985">{{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|article-number=28533 |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="Lucas" /> Beyond Utah and New Mexico,<ref name="Lucas" /><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 |volume=2006 }}</ref> other important US specimens have also been found in Arizona, eastern California,<ref name="Richards-1996" /><ref>{{Citation |last=Jefferson |first=George T. |title=Stratigraphy and paleontology of the middle to late Pleistocene Manix Formation, and paleoenvironments of the central Mojave River, Southern California |date=2003 |work=Paleoenvironments and paleohydrology of the Mojave and southern Great Basin deserts |url=https://pubs.geoscienceworld.org/books/book/509/chapter/3800872 |access-date=2024-07-18 |publisher=Geological Society of America |language=en |doi=10.1130/0-8137-2368-x.43 |isbn=978-0-8137-2368-6|url-access=subscription }}</ref><ref>{{Cite journal |date=26 March 2011 |title=Catalogue of Late Quaternary Vertebrates from California |url=http://sntbberry.cityofsanteeca.gov/sites/FanitaRanch/Public/Remainder%20of%20the%20Record/(2)%20Reference%20Documents%20from%20EIR%20&%20Technical%20Reports/Tab%20081%20-%201991%20Jefferson%20-%20Catalogue%20of%20Late%20Quaternary%20Vertebrates%20(revised%202020).pdf |journal=City of Santee}}</ref> Idaho,<ref name="Richards-1996" /> 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 |bibcode=2020WNAN...80..301E |s2cid=225958789 |issn=1527-0904|url-access=subscription }}</ref> and eastern 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 into central Mexico, with the Mexican Plateau sharing the Late Pleistocene mesic savanna and piñon–juniper woodland ecoregion with the southwestern USA.<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> While ''Arctodus'' was limited to the Mexican plateau, the typical tropical thorn scrub and scrub woodland of the plateau was seemingly prime habitat for tremarctine bears.<ref name="Esker-2010" /><ref name="Adams, J.M.-2001">{{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><ref name="Eng-Ponce-2021">{{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> An ''Arctodus simus'' individual from Cedral, San Luis Potosí, inhabited closed vegetation, with its diet possibly incorporating local C<sub>3</sub> specialists such as tapir, llamas, camels, and Shasta ground sloth along with browsed vegetation. The site hosted an open gallery forest near grassland or scrub with a humid climate.<ref name="Pérez-Crespo-2018" /> Similar highland remains have been recovered from 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> Michoacán,<ref name="Eng-Ponce-2021" /> Puebla,<ref name="Richards-1996" /> 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 Zacatecas.<ref name="Pedersen 2728–2736.e8" />
==== Interior Plains ==== The Interior Plains were composed of temperate steppe grassland,<ref name="Adams, J.M.-2001" /> 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 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> ''A. simus'' co-existed with ground sloths (''Megalonyx'', ''Paramylodon''), Pacific mastodon, 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 |article-number=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="Hill-2000">{{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 mammoths and horses dominated these 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> Additional Irvingtonian remains are from Kansas, Nebraska and Texas.<ref name="Scott-1993" /><ref name="Kurtén-1967" /><ref name="Richards-1996" />[[File:Wildflowers on ranchland, State Highway 965, Llano County, Texas, USA (13 April 2012).jpg|thumb|221x221px|''Arctodus'' also roamed the 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 mammoths, camels, ''Hemiauchenia'', and American pronghorns. While the northern plains aridified into cold steppe (e.g. Mammoth site, South Dakota),<ref name="Louguet-Lefebvre-2013">{{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) |journal=PALEO. Revue d'archéologie préhistorique |volume=24 |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 hackberry forests, and large expanses of mixed grass prairie grasslands grading into wet meadows, with limited seasonality. In the south (Lubbock Lake, Texas), this fauna was joined by ''Smilodon'', dire wolves, grey fox and red fox, preying upon prairie dogs, horses (''Equus'' & ''Haringtonhippus''), peccaries, ''Odocoileus'', ''Capromeryx'', ''Bison antiquus'' and ''Holmesina''.<ref name="Louguet-Lefebvre-2013" /><ref>{{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> A specimen from Friesenhahn Cave had a nitrogen-15 sample closest to the omnivorous striped skunk.<ref name="Smith-2022" /> 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|url-access=subscription }}</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="Richards-1996" /><ref>{{Cite journal |last=Taylor |first=D. W. |date=1960 |title=Late Cenozoic molluscan faunas from the High Plains |journal=USGS Report |page=4 |url=https://pubs.er.usgs.gov/publication/pp337 |doi=10.3133/pp337 |issn=2330-7102|doi-access=free |bibcode=1960usgs.rept....4T }}</ref> Nebraska,<ref name="Richards-1996" /> 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 |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>{{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|url-access=subscription }}</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 (''Mylohyus'', ''Platygonus''), giant beaver, porcupine, and American pine marten.<ref name="Tankersley-1997">{{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 |bibcode=1997Gearc..12..713T |url-access=subscription }}</ref><ref name="Redmond-2005">{{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 |bibcode=2005AmAnt..70..503R |s2cid=162034505 |issn=0002-7316|url-access=subscription }}</ref> Similar remains have been found in Alabama,<ref>{{Cite journal |last=Spry |first=Marla Jo |date=2000 |title=A Rancholabrean Cave Site in Northwest Alabama |url=https://www.cave-research.org/annual_reports/crf_ar_1994-97.pdf |journal=Cave Research Foundation: Annual Report 1994-1997 |publisher=Cave Books |pages=66–68 |isbn=0-939748-43-6}}</ref> Indiana,<ref name="Richards-1995" /> 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,<ref name="Esker-2010" /><ref name="Figueirido-2017" /> due to the high rate of preservation in the cave-rich region, particularly in Missouri.<ref name="Richards-1996" /> Irvingtonian trace fossils and claw-marks from Riverbluff Cave may be as old as 570,000 years old.<ref name="Lucas-2007" /><ref name=":19" /><ref name=":22" /><ref name=":25">{{Cite journal |last1=Rovey |first1=Charles W. |last2=Balco |first2=Greg |last3=Forir |first3=Matt |last4=Kean |first4=William F. |date=May 2017 |title=Stratigraphy, paleomagnetism, and cosmogenic-isotope burial ages of fossil-bearing strata within Riverbluff Cave, Greene County, Missouri |url=https://www.cambridge.org/core/product/identifier/S003358941700014X/type/journal_article |journal=Quaternary Research |language=en |volume=87 |issue=3 |pages=516–528 |doi=10.1017/qua.2017.14 |bibcode=2017QuRes..87..516R |issn=0033-5894}}</ref> Black bears were also very common, with ''A. simus'' has been found in association with black bears at Bat,<ref name=":18" /> Big Bear,<ref name="Schubert-2003" /> and Perkins caves.<ref name=":17">{{Cite journal |last=Hawksley |first=Oscar |date=July 1965 |title=Short-Faced Bear (Arctodus) Fossils from Ozark Caves |url=https://legacy.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="Schubert-2003" /> During the Last Glacial Maximum, both bears were joined by dire wolves, coyotes, jaguars, snowshoe hare, groundhogs and beavers at Bat Cave,<ref name=":18">{{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://legacy.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://npshistory.com/publications/paleontology/grdtr-01-02.pdf |journal=KIP Articles}}</ref> which also records thousands of ''Platygonus'' remains. These fauna inhabited well-watered forest-grassland ecotone with a strong taiga influence,<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 |article-number=e7161 |doi=10.7717/peerj.7161 |issn=2167-8359 |pmc=6612422 |pmid=31308997 |doi-access=free }}</ref> although the region did occasionally cycle through drier, grassier periods.<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> These open woodlands were dominated by pines and spruce, and to a lesser extent by oaks''.''<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> Additional finds have been recovered from Oklahoma.<ref name=":1" /><ref name=":2" />
==== Eastern North America ==== [[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="Schubert-2010a" /><ref name="Esker-2010" /><ref name="Figueirido-2017" /> To the north, the Appalachian Highlands were dominated by taiga.<ref name="Adams, J.M.-2001" /> Post-LGM Saltville, Virginia, was a mosaic of grassy/herb laden open areas intermixed with open canopy boreal woodlands (oaks, pines, spruce, birch, firs) and marshes. Inhabiting in this C<sub>3</sub> resource dominated environment were ''Arctodus simus'', mastodon, (southernmost) woolly mammoths, ''Bootherium,'' horses, caribou, ''Megalonyx'', dire wolves, beavers, ''Cervalces'', and a variety of warm-adapted reptiles, suggesting a more mesic and less seasonal climate than today. 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="Schubert-2009">{{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|url-access=subscription }}</ref> Beyond Virginia,<ref name="Schubert-2010b" /> additional remains have been found in Pennsylvania.<ref name="Richards-1996" /><ref name="Science-2010" /><ref>{{Cite journal |last=Tucci |first=Harry J. |date=1986 |title=Archaeological Investigations of Durham Cave #2 |url=https://liberalarts.tamu.edu/csfa/wp-content/uploads/sites/14/2023/07/CRP-3-1986.pdf |journal=Current Research in the Pleistocene |volume=3 |pages=25–26}}</ref>
To the south, the subtropical Atlantic Plains covered a great expanse of lowland, from the open deciduous woodlands of the 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 wolves, jaguars, ground sloths (''Megalonyx'', ''Paramylodon''), llamas (''Hemiauchenia'', ''Palaeolama''), Vero's tapir, giant beaver, capybara, ''Holmesina'', horses, ''Bison antiquus'', mastodon, Columbian mammoths and ''T. floridanus'', in a climate similar to today's. Furthermore, the abundance of black bears, and particularly ''T. floridanus'' in Florida, has led to a theorized niche partitioning of ursids in Florida, with ''T. floridanus'' being herbivorous, and black bears and ''A. simus'' being omnivorous, with ''Arctodus'' being possibly more inclined towards carnivory.<ref name="Schubert-2010a" /> Additional finds of south-eastern ''A. 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 |url-access=subscription }}</ref><ref>{{Cite journal |last=Kaye |first=John Morgan |date=1974 |title=Pleistocene Sediment and V ocene Sediment and Vertebrate Fossil 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="Seifert, M.-1962" /><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 kleptoparasitic relationship with Beringian wolves, akin to modern wolves and brown bears.]] Mostly isolated from the rest of North America, eastern Beringia (Alaska and the Yukon) was largely an extension of the mostly open and treeless 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 |url-access=subscription }}</ref> supporting a unique assemblage of fauna.<ref name="Churcher-2011">{{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|url-access=subscription }}</ref> 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="Salis-2020" /><ref name="Steffen-2018" /><ref name="Richards-1996" /><ref name="Stark-2022">{{Cite book |last=Stark |first=Mike |title=Chasing the Ghost Bear: On the Trail of America's Lost Super Beast |date=2022 |publisher=University of Nebraska Press |doi=10.2307/j.ctv2br108d |jstor=j.ctv2br108d |isbn=978-1-4962-2902-1|s2cid=247872305 }}</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="Paul-2001" /> Unlike contemporary Beringian carnivorans, ''A. simus'' apparently never inhabited western Beringia (and therefore Asia).<ref name="Paul-2001" /> The largest known skull of ''A. simus'' was recovered from the Yukon, and may represent the largest specimen known.<ref name="Sorkin-2006" /><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>
''A. simus'' is suggested to have been more carnivorous in Beringia than the rest of North America, in part due to elevated levels of nitrogen-15 recovered from specimens.<ref name="Bocherens-2015" /><ref name="Fox-Dobbs-2008" /><ref name="hb" /> 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="Figueirido-2017" /> No evidence of the carbohydrate-related dental pathologies have been found in Beringian ''A. simus''. However, few specimens exist, and seeds have been recovered from ''A. simus'' scat from the Yukon.<ref name="Figueirido-2017" /><ref name=":16" /> 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 Alaskan brown bears.<ref name="Figueiridio_et_al_20102" /><ref name="Mychajliw-20202"/>
The 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. Cave lions, bears (''Ursus arctos'' and ''Arctodus simus''), and 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|url-access=subscription }}</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 |article-number=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 ''A. simus''<nowiki/>' Arctic diet,''<ref name="Fox-Dobbs-2008" /><ref name="Bocherens-2015" /><ref name="hb" />'' suggesting that the warmer, wetter vegetation on the margins of the dry mammoth steppe (similar to the moist acidic tundra vegetation which dominates today) was the preferred habitat of ''Arctodus'' in Beringia.<ref name="Bocherens-2015" /><ref name="sciencedirect.com" /> 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="Bocherens-2015" />
The co-ecologies of brown bears and ''A. simus'' in Beringia has also been examined. Isotope values in numerous Beringian ''Arctodus simus'' specimens suggests ''A. simus'' usually occupied a higher trophic level compared with invading brown bears. While the diet of Beringian brown bears was diverse (with some individuals consuming salmon), the data suggests that only terrestrial sources of meat were important for Beringian ''Arctodus''.<ref name="Matheus-1995" /> Researchers drew parallels with modern brown bears and American black bears.<ref name="Matheus-1997" /><ref name="Bocherens-2015" /> Where they overlap, black bears take the lower trophic niche, with lower population densities, much smaller territorial ranges, and seasonal migrations.<ref name="Kubiak-2022" />
Additionally, upon the flooding of the Bering Strait and expansion of moist tundra and peatlands in eastern Beringia during MIS-3, lions, brown bears and ''Homotherium'' went regionally extinct ~35,000 BP, whereas wolves and ''Arctodus'' persisted. Simultaneously, most megafaunal herbivores in Beringia experienced population bottlenecks. This restriction of prey and habitat could explain the extinctions. However, genetically distinct cave lions and brown bears appear in 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="Salis-2020" /><ref name="Bocherens-2015" /><ref name="Murchie-2021">{{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="Barnes-2002">{{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|url-access=subscription }}</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 |bibcode=2007CBio...17.1146L |hdl=10261/61282 |hdl-access=free }}</ref> The idea that ''Arctodus'' had a kleptoparasitic relationship with wolves and ''Homotherium'' in Beringia has been explored,<ref name="Bocherens-2015" /> with the additional possibility that ''Arctodus'' successfully competed against brown bears and ''Homotherium'' for access to caribou pre-LGM.<ref name="Fox-Dobbs-2008">{{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|url-access=subscription }}</ref> The lack of ''Arctodus'' in Siberia and cave hyena in North America may be due to competitive exclusion,<ref name="Baryshnikov-1994" /> however many other fauna did not cross the Rancholabrean Beringian gap, such as the American badger, ''Bootherium'' and the woolly rhino.<ref>{{Cite journal |last1=Stuart |first1=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 |bibcode=2012QSRv...51....1S |doi=10.1016/j.quascirev.2012.06.007 |issn=0277-3791 |url-access=subscription}}</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 |url-access=subscription}}</ref>
The local extinction of ''Arctodus'' in Beringia ~23,000 BP (possibly due to sharp climatic cooling associated with Heinrich Event-2),<ref name="Salis-2020" /><ref name="Steffen-2018" /> was much earlier than in other parts of its range. While recolonized by cave lions and brown bears from Eurasia, ''Arctodus'' did not repopulate Beringia once the ice-free corridor to the south re-opened later in the Pleistocene.<ref name="Salis-2020" /><ref>{{Cite journal |last1=Pedersen |first1=Mikkel W. |last2=Ruter |first2=Anthony |last3=Schweger |first3=Charles |last4=Friebe |first4=Harvey |last5=Staff |first5=Richard A. |last6=Kjeldsen |first6=Kristian K. |last7=Mendoza |first7=Marie L. Z. |last8=Beaudoin |first8=Alwynne B. |last9=Zutter |first9=Cynthia |last10=Larsen |first10=Nicolaj K. |last11=Potter |first11=Ben A. |date=2016 |title=Postglacial viability and colonization in North America's ice-free corridor |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> When brown bears recolonized Beringia ~23,000 BP, they 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="Salis-2020" /><ref name="Steffen-2018" />
== 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: 8px ''A. pristinus'' (Late Blancan / Irvingtonian)
8px Early/Middle Pleistocene (Irvingtonian) ''A.simus''
8px Late Pleistocene (Rancholabrean) ''A. simus''
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 (type locality (+ Samwell Cave & Stone Man 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 = Duck Flat | position = none | lat= 41.016508 | long= -119.884385 | mark= Red_pog.svg}} {{location map~ |North America| label = Durnham Cave #1 | position = none | lat= 40.585846 | long= -75.244704 | 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 Bear II (ACb-3) | position = none | lat= 34.7197 | long= -87.7678 | 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 = 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 = 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 = Drews Gap (footprints, Lakeview) | position = none | lat= 42.19927 | long= -120.615498 | mark= Blue_pog.svg}} {{location map~ |North America| label = El Casco fauna? (San Timoteo) | position = none | lat=33.966496 | long= -117.077414| mark= Blue_pog.svg}} {{location map~ |North America| label = Elsinore | position = none | lat=33.555556 | long= -117.211111| 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 = 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 (Briscoe County) | 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 = Riverbluff Cave | position = none | lat= 37.106298 | long= -93.32927 | 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 = Hamilton Cave | position = none | lat=38.542722 | long= -79.450204 | 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 = Middle Loup River (Mullen Local Fauna / North Prong Quarry) | position = none | lat=42.1189 | long= -101.186 | 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 = Hay Springs| position = none | lat=42.7 | long= -102.5 | mark= Blue_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 = Pendejo Cave | position = none | lat= 32.416667 | long= -105.916667 | mark= Red_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 in the south-east of North America, whereas the black bear was more common in the north-east.<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> The black bear has inhabited North America since at least the Middle Pleistocene,<ref name="Kubiak-2022" /> 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="Emslie-1995" />
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 ''T. 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="Emslie-1995" /> ''T. floridanus'' was possibly an ecological replacement of ''A. pristinus'', with ''T. floridanus'' finds being widespread in Rancholabrean Florida and the wider southeastern United States.<ref name="Emslie-1995" /><ref name="Russell-2009" /><ref name="Esker-2010" />
=== ''Arctodus simus'' === thumb|The brown bear was a direct competitor of ''Arctodus simus''.The most commonly accepted ecological parallel of ''Arctodus simus'' in scientific literature is the brown bear.<ref name="Figueiridio_et_al_20102" /><ref name="FIGUEIRIDO-2009" /><ref name="Steffen-2018" /> Both brown bears and ''A. simus'' exhibit a high degree of dietary variability, and while largely herbivorous, meat can be an important dietary element to certain populations of both species.<ref name="Bocherens-2015" /> 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="Matheus-1997" /><ref name="Bocherens-2015" /> One past theory behind the extinction of ''A. 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="Kurten-1974" />
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="Salis-2020" /><ref name="Steffen-2018" /> Brown bears (along with lions, bison and red foxes) first emigrated to North America via Beringia during the Illinoian Glaciation, with brown bears first arriving between ~177,000 BP and ~111,000 BP in eastern Beringia. Genetic divergences suggest brown bears first migrated south during MIS-5 (~92,000 - 83,000 BP) upon the opening of the ice-free corridor,<ref name="Salis-2020" /><ref name="Kubiak-2022" /> with the first fossils being near Edmonton (26,000 BP). On a continent-wide scale, although the brown bear and ''A. simus'' were sympatric at times as brown bears spread into North America, ''A. simus'' may typically have dominated competitive interactions, and displaced brown bears from specific localities.<ref name="Steffen-2018" /> For example, brown bear at the La Brea Tar Pits only postdate ''Arctodus''.<ref name="Lambert-1998">{{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 |bibcode=1998Ecosy...1..157L |doi=10.1007/s100219900012 |issn=1432-9840 |s2cid=29456831 |url-access=subscription}}</ref><ref name="Kurten-1974" /><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> 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="Steffen-2018" /> Brown bears and ''Arctodus'' have been discovered together in Alaska (then Beringia) between 50,000 BP and 34,000 BP,<ref name="Salis-2020" /> and in later Pleistocene deposits in California, Nevada, Vancouver Island, and Wyoming.<ref name="Richards-1996" /><ref name="Steffen-2018" /><ref name="Kurten-1974" />
=== <small>Convergent evolution</small> === [[File:Arctodus Simus, Hot Springs, South Dakota.jpg|thumb|''Arctodus simus'' reconstruction at the Hot Springs Mammoth Site, South Dakota.]] While both ''Arctodus'' and ''Arctotherium'' may have convergently evolved huge body sizes,<ref name="Mitchell-2016" /> their inverse evolutionary trends towards body size between the Early and Middle Pleistocene suggests different selective pressures between North American and South American ecosystems.<ref name="Soibelzon-2011" /> Additionally, there are notable differences between the giant short-faced bears ''Arctodus simus'' and ''Arctotherium angustidens''. 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 robust animal, in contrast with the gracile ''Arctodus simus''.<ref name="Soibelzon-2011" /> 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="Soibelzon-2009">{{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="Soibelzon-2009" /><ref name="FIGUEIRIDO-2009" /> Massive body size appears to be less frequent in ''A. simus'' than in ''A. angustidens''.<ref name="Soibelzon-2011" />
''Arctodus simus'' has also been suggested to share ecomorphological convergences with other extinct bears (''Arctotherium bonariense,'' ''Agriotherium africanum'', and ''Huracan''). Together with great size, these species converged on several adaptations, including a skull with a short broad rostrum, premasseteric fossa on the mandible, possible carnassial shears (P4 and m1), and long limbs (relative to body length).<ref name="Sorkin-2006" /> Additionally, an analysis of the elbow joint of an indeterminate ''Arctodus'' specimen and several ''Arctotherium'' species suggested a mutual preference for mixed habitats.<ref name="Meloro 133–146" /> However, while ''Agriotherium'' and ''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="Jiangzuo-2023" />
== Interactions with humans == [[File:Clovis Point.jpg|thumb|The Clovis people are the first known culture to have interacted with ''Arctodus''.|left]]
=== Exploitation === Several ''A. simus'' remains document evidence of consumption by humans. The most famous example comes from Lubbock Lake Landmark, Texas. An ''Arctodus simus'' was processed for subsistence (butchery marks indicated skinning, de-fleshing and disarticulation) and tool production by Clovis people, much in the same way as a mammoth carcass (~13,000 BP / 11,100 <sup>14</sup>C BP ).<ref name="Arroyo-Cabrales-2016">{{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> Additional remains of consumed ''A''. ''simus'' include a charred ''A. simus'' footbone fragment recovered from Spalding, Idaho,<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 |page=51}}</ref><ref>{{Cite journal |last1=Chadez |first1=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 |bibcode=2017JArSR..16..258C |issn=2352-409X|url-access=subscription }}</ref> along with ''A. simus'' hair in a cooking pit from Pendejo Cave, New Mexico.<ref>{{Cite book |last1=MacNeish |first1=Richard S. |url=https://books.google.com/books?id=2tQLRHdQxD4C&q=short-faced+bear&pg=PA461 |title=Pendejo Cave |last2=Libby |first2=Jane G. |last3=Liddy |first3=Jane G. |date=2003 |publisher=UNM Press |isbn=978-0-8263-2405-4 |language=en}}</ref> Other remains of ''A. simus'' have been found in association with Paleo-Indian artifacts in Sheriden Cave, Ohio,<ref name="Tankersley-1997" /><ref name="Redmond-2005" /><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="Gillette-1992" /> The direct relationship between humans and some associated ''Arctodus'' remains has been occasionally 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 |url-access=subscription }}</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|url-access=subscription }}</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 |bibcode=2017QuInt.444...72R |issn=1040-6182|url-access=subscription }}</ref>
=== Competition === Human hunting and butchery of large megafauna, particularly mammoths and mastodon, would likely have put people in competition with ''A. simus''. Defense against these large bears and the abandonment of carcasses are plausible outcomes,<ref name="Steffen-2018" /> along with the possible caching and disposal of carcass remains underwater to mask its odor from ''Arctodus''.<ref name=":15">{{Cite journal |last1=Kenady |first1=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|bibcode=2011QuInt.233..130K |url-access=subscription }}</ref>
==== Migration barrier hypothesis ==== In the late 1980s, Val Geist hypothesized that "specialist, aggressive, competitive Rancholabrean fauna" such as ''Arctodus simus'' 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 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 ''A. simus'' and other large Pleistocene North American carnivores, making human expansion difficult in Beringia and impossible south of the ice sheets.<ref name="Steffen-2018" /><ref name="Matheus-1997" /><ref name="Paul-2001" />
However, this theory has never been accepted by anthropologists. Paul Matheus argues that there were negligible ecological differences across the mammoth steppe, and that humans successfully competed against and even hunted territorial cave bears, cave hyenas, cave lions, leopards, tigers and wolves in Eurasia before reaching eastern Beringia, making the solitary ''Arctodus'' an unlikely impediment to expansion.<ref name="Paul-2001">{{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, both humans and ''A. simus'' are first dated to ~50,000 BP in Beringia, both from sites in the Yukon, and co-existed until ''A. simus'' 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 scimitar-tooth cats.<ref name="Salis-2020" />
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 footprints in New Mexico, dated to ~22,000 cal. BP,<ref name="Pigati-2023">{{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|url-access=subscription }}</ref> affirming that humans proliferated alongside megafauna (such as ''Arctodus'') in southern North America for more than ten thousand years.<ref name="Boëda-2021">{{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 |issn=2055-5563 |s2cid=230533453 |url-access=subscription}}</ref><ref name="Gruhn-2023">{{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 |issn=2055-5563 |s2cid=265285459 |url-access=subscription}}</ref><ref name="Gruhn-2020">{{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 |bibcode=2020Natur.584...47G |doi=10.1038/d41586-020-02137-3 |issn=0028-0836 |pmid=32699366 |s2cid=220717778 |url-access=subscription}}</ref><ref name="Rowe-2022">{{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 |bibcode=2022FrEEv..1003795R |doi=10.3389/fevo.2022.903795 |issn=2296-701X |doi-access=free |article-number=903795}}</ref><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|url-access=subscription }}</ref> Humans were definitively widespread across the Americas by at least 15,000 BP.<ref name="Steffen-2018" /><ref name="Gruhn-2023" /><ref name="Pansani-2023">{{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 |article-number=20230316}}</ref>
=== Oral traditions === Stories of giant bears present in the oral traditions of the Haudenosaunee, Lakota and Ojibwe may be potential cultural memories of interactions between humans and ''A. simus'',<ref>{{Cite book |last=Landol |first=Nicholas |url=https://www.researchgate.net/publication/368392074 |title=The Role of the Pleistocene in Native American Oral Traditions |date=October 27, 2022 |publisher=Binghamton University, State University of New York (Masters Thesis) |pages=33–36}}</ref> however stories of ''Katshituashku'' ("stiff-legged bear") amongst broader eastern Algonquian peoples may not represent links to extinct megafauna.<ref>{{Cite journal |last=SIEBERT Jr. |first=F. T. |date=1937 |title=Mammoth or "Stiff-Legged Bear" |url=https://onlinelibrary.wiley.com/doi/abs/10.1525/aa.1937.39.4.02a00410 |journal=American Anthropologist |language=en |volume=39 |issue=4 |pages=721–725 |doi=10.1525/aa.1937.39.4.02a00410 |issn=1548-1433}}</ref><ref>{{Cite journal |last=Lankford |first=George E. |date=1980 |title=Pleistocene Animals in Folk Memory |url=https://www.jstor.org/stable/540573 |journal=The Journal of American Folklore |volume=93 |issue=369 |pages=293–304 |doi=10.2307/540573 |jstor=540573 |issn=0021-8715}}</ref>
== Extinction ==
=== ''Arctodus pristinus'' === ''Arctodus pristinus'' went extinct in the Middle Pleistocene (300,000 years ago),<ref name="Schubert-2010a" /> being last recorded from the Coleman 2A site, Florida.<ref>{{Citation |last1=Karrow |first1=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.|url-access=subscription }}</ref> The evolution of ''Arctodus simus'', competition with ''Tremarctos floridanus'' and 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 ''A. pristinus'' in the late Irvingtonian faunal stage.<ref name="Schubert-2010a" /><ref name="Esker-2010" /> There are dubious records of ''A. pristinus'' in South Carolina and California from the Late Pleistocene,<ref name="Sanders-2002" /><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="Albright-2020" /><ref name="Mychajliw-20202"/> Modern research establishes ''A. pristinus'' as existing between the Pliocene-Pleistocene boundary and the Middle Pleistocene.<ref name="Emslie-1995" /><ref name="Schubert-2010a" /><ref name="Albright-2020" />
=== ''Arctodus simus'' === thumb|Skeletal reconstruction of ''Arctodus simus.''With the extinction of ''Arctodus pristinus'', ''A. simus'' became the final representative of the genus. ''A 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 Pleistocene-Holocene boundary (13,800 BP - 11,400 BP).<ref name="Stuart-2015">{{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|url-access=subscription }}</ref><ref name="Faith-2009">{{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|url-access=subscription }}</ref> ''A. simus'' is one of 9 species which represent over 85% of dated megafaunal remains between 20,000 and 10,000 years ago.<ref name=":28" /> Both local and regionalized dietary flexibility has been a factor suggested for the species' longevity.<ref name="Figueirido-2017" />
Various factors, including the depletion in number of large herbivores,<ref name="Lambert-1998" /><ref name="Mattson-1998" /> 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="Arroyo-Cabrales-2016" /> However, multiple studies put doubt on brown bears being culpable in ''A. simus''<nowiki/>' extinction, with the brown bear being more of an ecological replacement that was more adaptable to change.<ref name="Esker-2010" /><ref name="Steffen-2018" /><ref name="Mattson-1998" /> 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 ''A. simus''.<ref name="Steffen-2018" /> Additionally, dental wear evidence from Rancho La Brea does not suggest that food shortages were to blame for the demise of large bodied carnivorans such as ''A. 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 woodlands with abundant lodgepole pine to increasingly closed forests with shade-tolerant spruce, mountain hemlock, and red alder. These changes, effective by ~12,450 BP, point toward cool and moist conditions during the Younger Dryas stadial. Closed forests continued to expand in the early Holocene. Even though ''A. 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 ''A. simus'', along with many other megafauna.<ref name="Steffen-2018" />
==== Low genetic diversity ==== thumb|201x201px|Low genetic diversity could have hastened ''Arctodus''<nowiki/>' extinction. ''A. simus'' had a low level of genetic diversity from most sampled specimens,<ref name=":11" /><ref name="Bray-2010" /> with a genetic study suggesting an extended history of low effective population size.<ref name=":13" /> 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="Bray-2010" /><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 |journal=Quaternary International |volume=647-648 |language=en |pages=71–80 |doi=10.1016/j.quaint.2021.11.017|s2cid=244706923 |doi-access=free }}</ref> That the southern specimens were very closely related to Beringian specimens may further support this idea, as these populations had been isolated from before the Last Glacial Maximum (last common ancestor - 31,500 BP).<ref name="Bray-2010">{{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><ref name=":11" />
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, sympatric source populations in Eurasia, with a high genetic (mitochondrial) diversity of Beringian brown bears in contrast with Beringian ''A. simus''. This contrast in genetic diversity may also suggest that while female brown bears have a permanent home range, female ''A. simus'' may not have.<ref name=":11" /><ref name="Bray-2010" /><ref name="Salis-2020" /> If ''Arctodus simus'' experienced genetic bottlenecks or local extinctions prior to the Last Glacial Maximum, ''A. simus'' 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="Bray-2010" />
==== Overkill hypothesis ==== A 2025 study found that diurnality and a high basal metabolic rate (BMR) were traits reliably shared amongst extinct Pleistocene carnivorans, with ''A. simus'' having the highest BMR of all the studied fauna. As both these extinct predators and humans primarily operated during daylight hours and required intensive foraging to sustain their energy demands, these predators would have disproportionately increased exposure to human competition, and a reduced resilience to even moderate hunting pressure during the Pleistocene.<ref>{{Cite journal |last1=Todorov |first1=Orlin S. |last2=Alroy |first2=John |date=2025 |title=Extinct Pleistocene carnivores were diurnal and highly active |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/ecog.08061 |journal=Ecography |language=en |volume=2025 |issue=12 |article-number=e08061 |doi=10.1002/ecog.08061 |bibcode=2025Ecogr202508061T |issn=1600-0587}}</ref>
==== Last dates ==== The youngest date for ''A. simus'' is circa 12,700 BP from Friesenhahn Cave, Texas, calibrated from 10,814 ± 55 radiocarbon years (<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, was dated to ca. 12,800 BP (based on 10,921 ± 50 radiocarbon years) from well preserved collagen. However, the same vertebra was previously assigned a younger date of ca. 10,980 BP (9,630 ± 60 radiocarbon years) from a different laboratory, which widens the possible age of this vertebra to between 9,510 and 11,021 <sup>14</sup>C BP (at 2''σ'').<ref name="Schubert-2010b" /><ref name=":28">{{Cite journal |last1=Broughton |first1=Jack M. |last2=Weitzel |first2=Elic M. |date=21 December 2018 |title=Population reconstructions for humans and megafauna suggest mixed causes for North American Pleistocene extinctions |journal=Nature Communications |language=en |volume=9 |issue=1 |page=5441 |doi=10.1038/s41467-018-07897-1 |issn=2041-1723 |pmc=6303330 |pmid=30575758 |bibcode=2018NatCo...9.5441B }} Refer Supplementary Table 1</ref> Nevertheless, a specimen from 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="Schubert-2010b" /><ref name="Stuart-2015" />
== History of research ==
=== Subspecies hypothesis === [[File:DSC09100 - Extinct Bear (37221999825).jpg|thumb|Skeletal reconstruction of ''Arctodus simus'' at the Royal Ontario Museum, Toronto.]]Size differences between specimens of ''Arctodus simus'' (such as skull and long bone dimensions) led Kurtén to propose two forms; a larger subspecies emerged in the Irvingtonian (''A. s. yukonensis''), which was then displaced in the south by a smaller subspecies (''A. s. simus'') during the Rancholabrean epoch.<ref name="Kurtén-1967" /><ref name="Richards-1996" /><ref name="Figueiridio_et_al_20102" /> An additional subspecies (''A. s. nebrascensis'') was described by Childs Frick.<ref>{{Cite journal |last1=Schultz |first1=C. Bertrand |last2=Lueninghoener |first2=Gilbert C. |last3=Frankforter |first3=W. D. |date=July 1951 |title=A Graphic Résumé of the Pleistocene of Nebraska (With Notes on the Fossil Mammalian Remains) |url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1097&context=museumbulletin |journal=Bulletin of the University of Nebraska State Museum |volume=3 |issue=6 |pages=Table 1}}</ref><ref>{{Cite journal |last1=Schultz |first1=C. Bertrand |last2=Tanner |first2=Lloyd G. |date=September 1957 |title=Medial Pleistocene Fossil Vertebrate Localities in Nebraska |url=https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1020&context=museumbulletin |journal=Bulletin of the University of Nebraska State Museum |volume=4 |issue=4 |page=71}}</ref> Other theories, such as the sexual dimorphism and individual variation known from Tremarctine bears, potential ecomorphs, and the overall lack of finds were additional factors used to explain the significant variation in ''Arctodus''.<ref name="Emslie-1995" /><ref name="Richards-1996" /><ref name="Nelson-1983" />
However, sexual dimorphism has been described in ''A. pristinus''.<ref name="Emslie-1995" /> Additionally, the presence of very large southern ''A. simus'' specimens (in California,<ref name="Richards-1996" /><ref name="Scott-1993" /><ref name=":12" /> Florida,<ref name="Schubert-2010a" /> and New Mexico)<ref name="Lucas" /> and notably small northern specimens (Yukon and Vancouver Island)<ref name="Pedersen 2728–2736.e8" /><ref name="Steffen-2018" /> already put doubt on this designation,<ref name="Paul-2001" /> with the low number of specimens and sex-biased sampling potentially leading to perceived ecomorphologies.<ref name="Schubert-2010a" /> For example, 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 (penis bones) would likely be found if present, suggesting that mostly female individuals of ''A. simus'' were using caves.<ref name="Schubert-2003" /><ref name="Fowler-2021" /><ref name="Richards-1996" /> The only baculum currently known from ''A. simus'' may belong to a black bear (Potter Cave),<ref name="Stark-2022" /> while DNA evidence currently only affirms female specimens as having been recovered from caves.<ref name=":11" /> Sexual dimorphism also explained why ''Arctodus'' teeth (from multiple individuals at the same site) generally clustered into two sizes.<ref name="Emslie-1995" /><ref name="Richards-1996" /> While Rancho La Brea (the locality with the highest number of ''A. simus'' specimens) is the only site to preserve both size classes, radiocarbon dates confirm both sizes coexisted temporally, and were therefore sexes.<ref name=":12" /> A 2025 mitochondrial DNA study found sexually dimorphic size classes and a uniform population from at least 31 individuals (derived from 28 deposits across the United States and Canada), further affirming sexual dimorphism in ''A. simus''.<ref name=":11" />
=== "Super predator" hypothesis === One past proposal envisaged ''Arctodus simus'' as a brutish predator that overwhelmed very large but slow megafauna with its great physical strength.<ref name="Matheus-2003" /> However, despite being very large, its limbs were too gracile for such an attack strategy,<ref name="Matheus-2003" /><ref name="Lynch-2012" /><ref name="Paul-2001" /> significantly more gracile so than ''Arctotherium angustidens'' at that.<ref name="Soibelzon-2011" />
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 horses and saiga antelopes, an idea that at one time earned it the name "running bear".<ref name="Mattson-1998" /><ref name="Figueiridio_et_al_20102" /><ref name="North American Bear Center-2018" /> However, during pursuit of speedy game animals, the bear's sheer physical mass, inflexible spine and plantigrade gait would be a handicap; modern brown bears 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="Sorkin-2006" /><ref name="Matheus-2003" /> 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="Emslie-1985" /><ref name="Sorkin-2006" /><ref name="Jiangzuo-2023" />
Furthermore, the lack of definitive predatory adaptions (such as the absence of laterally compressed canines, and carnassials built for crushing and grinding rather than shearing meat) puts doubt to any species-wide hyper-carnivorous interpretations of ''A. simus.''<ref name="Figueiridio_et_al_20102" /><ref name="Meloro 133–146" /><ref name="Sorkin-2006" /><ref name="Figueirido-2008" /> The anatomical requirements for a large, cursorial, hyper-carnivorous bear are present in ''Huracan'' and ''Agriotherium'', but not ''Arctodus''.<ref name="Jiangzuo-2023" /><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|url-access=subscription }}</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="Figueirido-2008" /> Although the only living hyper-carnivorous ursid, the polar bear, also lacks carnassial shears, the species' specialization on small prey and reliance on blubber (rather than coarser flesh) invalidates this comparison with ''Arctodus''.<ref name="Emslie-1985" /><ref name="Sorkin-2006" /><ref name="Figueirido-2008" /> However, both ''Arctodus simus'' and polar bears may have had similar overall limb proportions.<ref name=":0" /> Regardless, carnivory was likely limited to the regular scavenging of carcasses and opportunistic hunting, as is the case with the modern brown bear.<ref name="Mattson-1998" /><ref name="Figueiridio_et_al_20102" /><ref name="Sorkin-2006" />
=== Specialist kleptoparasite vs Omnivore === [[File:Mammut_americanum_humerus_with_tooth_marks.jpg|left|thumb|Mastodon arm bone from the Snowmastodon site with predator damage at the Denver Museum of Nature & Science in Denver, Colorado.]] The idea that ''Arctodus simus'' was an obligate kleptoparasite was most notably proposed by Paul Matheus.<ref name="Simus2" /> Under this model, ''A. 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 mega-mammal carcasses.<ref name="Sorkin-2006" /> 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="Matheus-2003" /> Matheus calculated that with a 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 horses, or 2 woolly mammoths (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="Matheus-1997" /><ref name=hb/>
Furthermore, the short rostrum, resulting in increased out-forces of the jaw-closing muscles (temporalis and masseter), may have been an adaptation for cracking bones with their broad carnassials. 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="Sorkin-2006" /> Additionally, strengthened tooth enamel in ''Arctodus'' may have evolved to crack bone.<ref name="Stefen-2001" /> Moreover, at least in Beringia, the conservative growth strategies, long lives and low natural mortality rates of horses and mammoths should have provided somewhat evenly distributed carcasses throughout the year (unlike ruminants such as bison, whose mortality peaks in late winter to early spring).<ref name="Matheus-1997" />
==== Rebuttal ==== [[File:Shortfacedbear-1070375.jpg|thumb|226x226px|Clues from ''Arctodus''<nowiki/>' dentition, such as the absence of molar damage associated with processing bone, dental cavities, and the lack of specialisation in the canines, discourages a hyper-carnivorous interpretation of ''Arctodus''.]]
The kleptoparasite hypothesis has been repeatedly challenged. The short, broad rostrum of ''Arctodus'' is a characteristic also shared with the sun bear and the spectacled bear, which are both omnivorous.<ref name="Figueiridio_et_al_20102" /> Specialized scavengers like hyenas show distinctive patterns of molar damage from cracking bones. Based on lack of "bone-cracking" wear in specimens from Rancho La Brea, researchers in 2013 concluded that ''A. 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="Emslie-1985" /><ref name="Donohue2" />
Additionally, severe tooth crown fractures and alveolar infections were found in the South American giant short-faced bear (''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" /><ref name="Kurten-1974" /> Instead, recovered dental damage (incisor wear, dental calculus & cavities) is herbivorous in origin.<ref name="Schubert-2003" /><ref name="Figueirido-2017" /><ref name="Steffen-2018" /> 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="DeSantis-2015" />
Furthermore, the relative lack of ''Arctodus'' remains at predator traps such as the La Brea Tar Pits, suggests that ''Arctodus'' did not regularly compete for carcasses.<ref name="Figueirido-2017" /> 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="DeSantis-2015" /> While more abundant than brown bears and 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|url-access=subscription }}</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="Bocherens-2015" /> 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 |article-number=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'' * Eurasian cave bear * Polar bear * Quaternary Extinction Event
==References== {{Reflist}}
== External links == {{commons category|Arctodus}}
{{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:Extinct apex predators Category:Extinct animals of Canada Category:Tremarctinae Category:Species that are or were threatened by climate change