Editing Megafauna

{{short description|Large animals}}
{{about|living or extinct large animals}}
{{pp-protected|small=yes}}
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[[File:Ngorongoro Crater, Tanzania (2288421918).jpg|thumb|320px|The [[African bush elephant]] (foreground), Earth's largest extant land animal, and the [[Masai ostrich]] (background), one of Earth's largest extant birds]]
In [[zoology]], '''megafauna''' (from [[Ancient Greek|Greek]] μέγας ''megas'' "large" and [[Neo-Latin]] ''[[fauna]]'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately {{Convert|45|kg}}, this lower end being centered on humans, with other thresholds being more relative to the sizes of animals in an ecosystem,<ref name="g936">{{cite journal | last=Moleón | first=Marcos | last2=Sánchez-Zapata | first2=José A. | last3=Donázar | first3=José A. | last4=Revilla | first4=Eloy | last5=Martín-López | first5=Berta | last6=Gutiérrez-Cánovas | first6=Cayetano | last7=Getz | first7=Wayne M. | last8=Morales-Reyes | first8=Zebensui | last9=Campos-Arceiz | first9=Ahimsa | last10=Crowder | first10=Larry B. | last11=Galetti | first11=Mauro | last12=González-Suárez | first12=Manuela | last13=He | first13=Fengzhi | last14=Jordano | first14=Pedro | last15=Lewison | first15=Rebecca | last16=Naidoo | first16=Robin | last17=Owen-Smith | first17=Norman | last18=Selva | first18=Nuria | last19=Svenning | first19=Jens-Christian | last20=Tella | first20=José L. | last21=Zarfl | first21=Christiane | last22=Jähnig | first22=Sonja C. | last23=Hayward | first23=Matt W. | last24=Faurby | first24=Søren | last25=García | first25=Nuria | last26=Barnosky | first26=Anthony D. | last27=Tockner | first27=Klement | title=Rethinking megafauna | journal=Proceedings of the Royal Society B: Biological Sciences | volume=287 | issue=1922 | date=March 11, 2020 | issn=0962-8452 | pmid=32126954 | pmc=7126068 | doi=10.1098/rspb.2019.2643 | doi-access=free | page=20192643 | url=https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2019.2643 | access-date=May 9, 2025}}</ref> the spectrum of lower-end thresholds ranging from {{Convert|10|kg|lb}} to {{Convert|1,000|kg|lb}}. Large body size is generally associated with other traits, such as having a slow rate of reproduction and, in large herbivores, reduced or negligible adult mortality from being killed by predators.

Megafauna species have considerable effects on their local environment, including the suppression of the growth of woody vegetation and a consequent reduction in [[wildfire]] frequency. Megafauna also play a role in regulating and stabilizing the abundance of smaller animals.

During the [[Pleistocene]], megafauna were diverse across the globe, with most continental ecosystems exhibiting similar or greater [[species richness]] in megafauna as compared to ecosystems in Africa today. During the [[Late Pleistocene]], particularly from around 50,000 years ago onwards, [[Late Pleistocene extinctions|most large mammal species became extinct]], including 80% of all mammals greater than {{Convert|1,000|kg|lb}}, while small animals were largely unaffected. This pronouncedly size-biased extinction is otherwise unprecedented in the geological record. Humans and climatic change have been implicated by most authors as the likely causes, though the relative importance of either factor has been the subject of significant controversy.

== History ==
One of the earliest occurrences of the term "megafauna" is [[Alfred Russel Wallace]]'s 1876 work ''The geographical distribution of animals''. He described the animals as "the hugest, and fiercest, and strangest forms". In the 20th and 21st centuries, the term usually refers to large animals. There are variations in thresholds used to define megafauna as a whole or certain groups of megafauna. Many scientific literature adopt [[Paul Schultz Martin|Paul S. Martin]]'s proposed threshold of {{Convert|45|kg}} to classify animals as megafauna. However, for freshwater species, {{Convert|30|kg}} is the preferred threshold. Some scientists define herbivorous terrestrial megafauna as having a weight exceeding {{Convert|100|kg}}, and terrestrial carnivorous megafauna as more than {{Convert|15|kg}}. Additionally, Owen-Smith coined the term [[megaherbivore]] to describe herbivores that weighed over {{Convert|1000|kg}}, which has seen some use by other researchers.<ref name=":1">{{Cite journal |last1=Moleón |first1=Marcos |last2=Sánchez-Zapata |first2=José A. |last3=Donázar |first3=José A. |last4=Revilla |first4=Eloy |last5=Martín-López |first5=Berta |last6=Gutiérrez-Cánovas |first6=Cayetano |last7=Getz |first7=Wayne M. |last8=Morales-Reyes |first8=Zebensui |last9=Campos-Arceiz |first9=Ahimsa |last10=Crowder |first10=Larry B. |last11=Galetti |first11=Mauro |last12=González-Suárez |first12=Manuela |last13=He |first13=Fengzhi |last14=Jordano |first14=Pedro |last15=Lewison |first15=Rebecca |date=2020-03-11 |title=Rethinking megafauna |url=https://royalsocietypublishing.org/doi/10.1098/rspb.2019.2643 |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=287 |issue=1922 |pages=20192643 |doi=10.1098/rspb.2019.2643 |issn=0962-8452 |hdl-access=free |hdl=2263/79439}}</ref>

Among living animals, the term megafauna is most commonly used for the largest [[extant taxon|extant]] terrestrial mammals, which includes (but is not limited to) [[elephant]]s, [[giraffe]]s, [[hippopotamus]]es, [[rhinoceros]]es, and larger [[bovines]]. Of these five categories of large herbivores, only bovines are presently found outside of [[Africa]] and [[Asia]], but all the others were formerly more wide-ranging, with their ranges and populations continually shrinking and decreasing over time. Wild [[equines]] are another example of megafauna, but their current ranges are largely restricted to the [[Old World]], specifically in Africa and Asia. Megafaunal species may be categorized according to their dietary type: [[herbivores|megaherbivores]] (e.g., [[elephants]]), [[carnivores|megacarnivores]] (e.g., [[lion]]s), and [[omnivores|megaomnivores]] (e.g., [[bear]]s).<ref>{{Cite journal |last1=Malhi |first1=Yadvinder |last2=Doughty |first2=Christopher E. |last3=Galetti |first3=Mauro |last4=Smith |first4=Felisa A. |last5=Svenning |first5=Jens-Christian |last6=Terborgh |first6=John W. |date=2016-01-26 |title=Megafauna and ecosystem function from the Pleistocene to the Anthropocene |journal=Proceedings of the National Academy of Sciences |language=en |volume=113 |issue=4 |pages=838–846 |doi=10.1073/pnas.1502540113 |doi-access=free |issn=0027-8424 |pmc=4743772 |pmid=26811442|bibcode=2016PNAS..113..838M }}</ref><ref>{{Cite journal |last1=McClenachan |first1=Loren |last2=Cooper |first2=Andrew B. |last3=Dulvy |first3=Nicholas K. |date=2016-06-20 |title=Rethinking Trade-Driven Extinction Risk in Marine and Terrestrial Megafauna |journal=Current Biology |volume=26 |issue=12 |pages=1640–1646 |doi=10.1016/j.cub.2016.05.026 |issn=1879-0445 |pmid=27291051|bibcode=2016CBio...26.1640M |doi-access=free }}</ref>

==Ecological strategy==
Megafauna animals – in the sense of the largest mammals and birds – are generally [[K-strategists|''K''-strategists]], with high longevity, slow population growth rates, low mortality rates, and (at least for the largest) few or no natural predators capable of killing adults.<ref>{{Cite journal |last=Johnson |first=C. N. |date=2002-11-07 |title=Determinants of loss of mammal species during the Late Quaternary 'megafauna' extinctions: life history and ecology, but not body size |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |language=en |volume=269 |issue=1506 |pages=2221–2227 |doi=10.1098/rspb.2002.2130 |issn=0962-8452 |pmc=1691151 |pmid=12427315}}</ref><ref name=":1" /> These characteristics, although not exclusive to such megafauna, make them vulnerable to human [[overexploitation]], in part because of their slow population recovery rates.<ref name="Barnosky2004">{{cite journal|last1= Barnosky|first1=A. D.|title=Assessing the Causes of Late Pleistocene Extinctions on the Continents|journal= Science|volume= 306|issue=5693|date= 2004-10-01|pages= 70–75|doi= 10.1126/science.1101476|pmid=15459379|bibcode=2004Sci...306...70B|citeseerx=10.1.1.574.332|s2cid=36156087}}</ref><ref name="Brook2006">{{cite journal|last1= Brook|first1=B. W.|last2=Johnson|first2=C. N.|title=Selective hunting of juveniles as a cause of the imperceptible overkill of the Australian Pleistocene megafauna|journal= Alcheringa: An Australasian Journal of Palaeontology|volume= 30|issue= sup1|date= 2006|pages= 39–48|doi=10.1080/03115510609506854|bibcode=2006Alch...30S..39B |s2cid=84205755}}</ref>

==Evolution of large body size==
One observation that has been made about the evolution of larger body size is that rapid rates of increase that are often seen over relatively short time intervals are not sustainable over much longer time periods. In an examination of mammal body mass changes over time, the maximum increase possible in a given time interval was found to scale with the interval length raised to the 0.25 power.<ref name = "Evans2012"/> This is thought to reflect the emergence, during a trend of increasing maximum body size, of a series of anatomical, physiological, environmental, genetic and other constraints that must be overcome by evolutionary innovations before further size increases are possible. A strikingly faster rate of change was found for large decreases in body mass, such as may be associated with the phenomenon of [[insular dwarfism]]. When normalized to generation length, the maximum rate of body mass decrease was found to be over 30 times greater than the maximum rate of body mass increase for a ten-fold change.<ref name = "Evans2012"/>

===In terrestrial mammals===
[[File:Patagotitan vs Mammals Scale Diagram SVG Steveoc86.svg|thumb|upright=2|Large terrestrial mammals compared in size to one of the largest sauropod dinosaurs, ''[[Patagotitan]]'']]
Subsequent to the [[Cretaceous–Paleogene extinction event]] that eliminated the non-avian dinosaurs about {{period start|Paleogene}} [[Megaannum|Ma]] (million years) ago, terrestrial mammals underwent a nearly exponential increase in body size as they diversified to occupy the ecological niches left vacant.<ref name = "F.A.Smith">{{cite journal | last1=Smith|first1=F. A.|last2=Boyer|first2=A. G.|last3=Brown|first3=J. H.|last4=Costa|first4=D. P.|last5=Dayan|first5=T.|last6=Ernest|first6=S. K. M.|last7=Evans|first7=A. R.|last8=Fortelius|first8=M.|last9=Gittleman|first9=J. L.|last10=Hamilton|first10=M. J.|last11=Harding|first11=L. E.|last12=Lintulaakso|first12=K.|last13=Lyons|first13=S. K.|last14=McCain|first14=C.|last15=Okie|first15=J. G.|last16=Saarinen|first16=J. J.|last17=Sibly|first17=R. M.|last18=Stephens|first18=P. R.|last19=Theodor|first19=J.|last20=Uhen|first20=M. D.
  | title = The Evolution of Maximum Body Size of Terrestrial Mammals
  | journal = [[Science (journal)|Science]] | volume = 330 | issue = 6008 | pages = 1216–1219
  | date = 2010-11-26 | doi = 10.1126/science.1194830 |pmid=21109666|bibcode = 2010Sci...330.1216S|citeseerx=10.1.1.383.8581|s2cid=17272200}}</ref> Starting from just a few kg before the event, maximum size had reached ~{{Convert|50|kg|lb}} a few million years later, and ~{{Convert|750|kg|lb}} by the end of the [[Paleocene]]. This trend of increasing body mass appears to level off about 40 Ma ago (in the late [[Eocene]]), suggesting that physiological or ecological constraints had been reached, after an increase in body mass of over three orders of magnitude.<ref name = "F.A.Smith"/> However, when considered from the standpoint of rate of size increase per generation, the exponential increase is found to have continued until the appearance of ''[[Indricotherium]]'' 30 Ma ago. (Since generation time scales with ''body mass''<sup>0.259</sup>, increasing generation times with increasing size cause the log mass vs. time plot to curve downward from a linear fit.)<ref name = "Evans2012">{{cite journal
| last1=Evans|first1=A. R.|last2=Jones|first2=D.|last3=Boyer|first3=A. G.|last4=Brown|first4=J. H.|last5=Costa|first5=D. P.|last6=Ernest|first6=S. K. M.|last7=Fitzgerald|first7=E. M. G.|last8=Fortelius|first8=M.|last9=Gittleman|first9=J. L.|last10=Hamilton|first10=M. J.|last11=Harding|first11=L. E.|last12=Lintulaakso|first12=K.|last13=Lyons|first13=S. K.|last14=Okie|first14=J. G.|last15=Saarinen|first15=J. J.|last16=Sibly|first16=R. M.|last17=Smith|first17=F. A.|last18=Stephens|first18=P. R.|last19=Theodor|first19=J. M.|last20=Uhen|first20=M. D. 
 | title = The maximum rate of mammal evolution | journal = [[Proceedings of the National Academy of Sciences|PNAS]]
 | volume=109| issue=11| pages=4187–4190 | date = 2012-01-30
 | doi = 10.1073/pnas.1120774109 |pmid=22308461|pmc=3306709|bibcode=2012PNAS..109.4187E|doi-access=free}}</ref>

Megaherbivores eventually attained a body mass of over {{Convert|10,000|kg|lb}}. The largest of these, [[indricothere]]s and [[proboscid]]s, have been [[hindgut fermentation|hindgut fermenter]]s, which are believed to have an advantage over [[Foregut fermentation|foregut fermenter]]s in terms of being able to accelerate gastrointestinal transit in order to accommodate very large food intakes.<ref name = "Clauss">{{cite journal | last = Clauss | first = M. | author2 = Frey, R. | author3 = Kiefer, B. | author4 = Lechner-Doll, M. | author5 = Loehlein, W. | author6 = Polster, C. | author7 = Roessner, G. E. | author8 = Streich, W. J. | title = The maximum attainable body size of herbivorous mammals: morphophysiological constraints on foregut, and adaptations of hindgut fermenters | journal = [[Oecologia]] | volume = 136 | issue = 1 | pages = 14–27 | date = 2003-04-24 | doi = 10.1007/s00442-003-1254-z | pmid = 12712314 | bibcode = 2003Oecol.136...14C | s2cid = 206989975 | url = http://www.zora.uzh.ch/id/eprint/2393/2/Oecologia_body_size_2003V.pdf | access-date = 2019-07-13 | archive-date = 2019-06-08 | archive-url = https://web.archive.org/web/20190608152406/https://www.zora.uzh.ch/id/eprint/2393/2/Oecologia_body_size_2003V.pdf | url-status = dead }}</ref> A similar trend emerges when rates of increase of maximum body mass per generation for different mammalian [[clade]]s are compared (using rates averaged over [[macroevolution]]ary time scales). Among terrestrial mammals, the fastest rates of increase of ''body mass''<sup>0.259</sup> vs. time (in Ma) occurred in [[perissodactyl]]s (a slope of 2.1), followed by [[rodent]]s (1.2) and proboscids (1.1),<ref name = "Evans2012"/> all of which are hindgut fermenters. The rate of increase for [[artiodactyl]]s (0.74) was about a third of the perissodactyls. The rate for [[carnivora]]ns (0.65) was slightly lower yet, while [[primate]]s, perhaps constrained by their [[arboreal]] habits, had the lowest rate (0.39) among the mammalian groups studied.<ref name = "Evans2012"/>

Terrestrial mammalian carnivores from several [[eutheria]]n groups (the [[artiodactyl]] ''[[Andrewsarchus]]'' – formerly considered a [[Mesonychidae|mesonychid]], the [[oxyaenid]] ''[[Sarkastodon]]'', and the carnivorans ''[[Amphicyon]]'' and ''[[Arctodus]]'') all reached a maximum size of about {{Convert|1,000|kg|lb}}<ref name = "F.A.Smith"/> (the carnivoran ''[[Arctotherium]]'' and the [[hyaenodontid]] ''[[Simbakubwa]]'' may have been somewhat larger). The largest known [[metatheria]]n carnivore, ''[[Proborhyaena gigantea]]'', apparently reached {{Convert|600|kg|lb}}, also close to this limit.<ref name = "Sorkin"/> A similar theoretical maximum size for mammalian carnivores has been predicted based on the metabolic rate of mammals, the energetic cost of obtaining prey, and the maximum estimated rate coefficient of prey intake.<ref name = "Carbone">{{cite journal
  | last = Carbone | first = C. |author2=Teacher, A |author3=Rowcliffe, J. M.
  | title = The Costs of Carnivory | journal = [[PLOS Biology]]
  | volume = 5 | issue = 2, e22 | pages = 363–368
  | date = 2007-01-16 | doi = 10.1371/journal.pbio.0050022
  | pmid=17227145 | pmc=1769424 | doi-access = free }}</ref> It has also been suggested that maximum size for mammalian carnivores is constrained by the stress the [[humerus]] can withstand at top running speed.<ref name = "Sorkin">{{Cite journal
  | last = Sorkin | first = B.  | title = A biomechanical constraint on body mass in terrestrial mammalian predators
  | journal = [[Lethaia]] | volume = 41 | issue = 4 | pages = 333–347
  | date = 2008-04-10 | doi = 10.1111/j.1502-3931.2007.00091.x | bibcode = 2008Letha..41..333S }}</ref>

Analysis of the variation of maximum body size over the last 40 Ma suggests that decreasing temperature and increasing continental land area are associated with increasing maximum body size. The former correlation would be consistent with [[Bergmann's rule]],<ref name = "Ashton">{{cite journal
  | last = Ashton | first = K. G. |author2=Tracy, M. C. |author3=de Queiroz, A.
  | title = Is Bergmann's Rule Valid for Mammals?
  | journal = [[The American Naturalist]]
  | volume = 156 | issue = 4 | pages = 390–415
  | date = October 2000  | jstor = 10.1086/303400
  | doi = 10.1086/303400
  | pmid = 29592141 | s2cid = 205983729 }}</ref> and might be related to the [[Thermoregulation|thermoregulatory]] advantage of large body mass in cool climates,<ref name = "F.A.Smith"/> better ability of larger organisms to cope with seasonality in food supply,<ref name = "Ashton"/> or other factors;<ref name = "Ashton"/> the latter correlation could be explained in terms of range and resource limitations.<ref name = "F.A.Smith"/> However, the two parameters are interrelated (due to sea level drops accompanying increased glaciation), making the driver of the trends in maximum size more difficult to identify.<ref name = "F.A.Smith"/>

===In marine mammals===
[[File:Baleen whale sizes.JPG|thumb|upright=1.5|Baleen whale comparative sizes]]
Since tetrapods (first [[Marine reptile|reptiles]], later [[Marine mammal|mammals]]) returned to the sea in the [[Late Permian]], they have dominated the top end of the marine body size range, due to the more efficient intake of oxygen possible using lungs.<ref name = "Webb2015">{{Cite news | last = Webb | first = J. | title = Evolution 'favours bigger sea creatures' | publisher = [[BBC]] | date = 2015-02-19 | url = https://www.bbc.com/news/science-environment-31533744 | access-date = 2015-02-22 | work = BBC News | archive-date = 2015-02-22 | archive-url = https://web.archive.org/web/20150222044708/http://www.bbc.com/news/science-environment-31533744 | url-status = live }}</ref><ref name = "Helm2015">{{cite journal | last1 = Heim | first1 = N. A. | last2 = Knope | first2 = M. L. | last3 = Schaal | first3 = E. K. | last4 = Wang | first4 = S. C. | last5 = Payne | first5 = J. L. | title = Cope's rule in the evolution of marine animals | journal = Science | volume = 347 | issue = 6224 | pages = 867–870 | doi = 10.1126/science.1260065 | date = 2015-02-20 | pmid = 25700517 | bibcode = 2015Sci...347..867H | url = http://www.swarthmore.edu/NatSci/swang1/Publications/ | doi-access = free | access-date = 2019-07-13 | archive-date = 2019-07-05 | archive-url = https://web.archive.org/web/20190705023917/http://www.swarthmore.edu/NatSci/swang1/Publications/ | url-status = live }}</ref> The ancestors of [[cetacea]]ns are believed to have been the semiaquatic [[pakicetid]]s, no larger than dogs, of about 53 million years (Ma) ago.<ref name=poster>{{cite journal|last=Thewissen|first=J. G. M.|author2=Bajpai, S.|title=Whale Origins as a Poster Child for Macroevolution|journal=[[BioScience]]|date=1 January 2001|volume=51|issue=12|pages=1037–1049|doi=10.1641/0006-3568(2001)051[1037:WOAAPC]2.0.CO;2|issn=0006-3568|doi-access=free}}</ref> By 40 Ma ago, cetaceans had attained a length of {{cvt|20|m}} or more in ''[[Basilosaurus]]'', an elongated, serpentine whale that differed from modern whales in many respects and was not ancestral to them. Following this, the evolution of large body size in cetaceans appears to have come to a temporary halt and then to have backtracked, although the available fossil records are limited. However, in the period from 31 Ma ago (in the [[Oligocene]]) to the present, cetaceans underwent a significantly more rapid sustained increase in body mass (a rate of increase in ''body mass''<sup>0.259</sup> of a factor of 3.2 per million years) than achieved by any group of terrestrial mammals.<ref name = "Evans2012"/> This trend led to the largest animal of all time, the modern [[blue whale]]. Several reasons for the more rapid evolution of large body size in cetaceans are possible. Fewer [[Biomechanics|biomechanical]] constraints on increases in body size may be associated with suspension in water as opposed to standing against the force of gravity, and with [[Aquatic locomotion|swimming movements]] as opposed to [[terrestrial locomotion]]. Also, the greater heat capacity and thermal conductivity of water compared to air may increase the [[thermoregulation|thermoregulatory]] advantage of large body size in marine [[endotherm]]s, although diminishing returns apply.<ref name = "Evans2012"/>

Among the toothed whales, maximum body size appears to be limited by food availability. Larger size, as in [[sperm whale|sperm]] and [[beaked whale]]s, facilitates deeper diving to access relatively easily-caught, large cephalopod prey in a less competitive environment. Compared to odontocetes, the efficiency of baleen whales' [[filter feeding]] scales more favorably with increasing size when planktonic food is dense, making larger sizes more advantageous. The [[lunge feeding]] technique of [[rorqual]]s appears to be more energy efficient than the [[ram feeding]] of [[balaenid]] whales; the latter technique is used with less dense and patchy plankton.<ref name="Goldbogen2019">{{cite journal|last1= Goldbogen|first1=J. A.|last2= Cade|first2=D. E.|last3= Wisniewska|first3=D. M.|last4= Potvin|first4= J.|last5= Segre|first5=P. S.|last6= Savoca|first6=M. S.|last7= Hazen|first7=E. L.|last8= Czapanskiy|first8=M. F.|last9= Kahane-Rapport|first9=S. R.|last10= DeRuiter|first10=S. L.|last11= Gero|first11= S.|last12= Tønnesen|first12= P.|last13= Gough|first13=W. T.|last14= Hanson|first14=M. B.|last15= Holt|first15=M. M.|last16= Jensen|first16=F. H.|last17= Simon|first17= M.|last18= Stimpert|first18=A. K.|last19= Arranz|first19= P.|last20= Johnston|first20=D. W.|last21= Nowacek|first21=D. P.|last22= Parks|first22=S. E.|last23= Visser|first23= F.|last24= Friedlaender|first24=A. S.|last25= Tyack|first25=P. L.|last26= Madsen|first26=P. T.|author27-link=Nicholas Pyenson|last27= Pyenson|first27=N. D.|title= Why whales are big but not bigger: Physiological drivers and ecological limits in the age of ocean giants|journal= Science|volume= 366|issue= 6471|year= 2019|pages= 1367–1372|doi= 10.1126/science.aax9044|pmid=31831666|bibcode=2019Sci...366.1367G|hdl=10023/19285|s2cid=209339266|hdl-access= free}}</ref> The cooling trend in Earth's recent history may have generated more localities of high plankton abundance via wind-driven [[upwelling]]s, facilitating the evolution of gigantic whales.<ref name="Goldbogen2019" />

Cetaceans are not the only marine mammals to reach tremendous sizes.<ref>{{Cite journal |last1=Baker |first1=Joanna |last2=Meade |first2=Andrew |last3=Pagel |first3=Mark |last4=Venditti |first4=Chris |date=2015-04-21 |title=Adaptive evolution toward larger size in mammals |journal=Proceedings of the National Academy of Sciences |language=en |volume=112 |issue=16 |pages=5093–5098 |doi=10.1073/pnas.1419823112 |doi-access=free |issn=0027-8424 |pmc=4413265 |pmid=25848031|bibcode=2015PNAS..112.5093B }}</ref> The largest mammal [[carnivora]]ns of all time are marine [[pinniped]]s, the largest of which is the [[southern elephant seal]], which can reach more than {{cvt|6|m}} in length and weigh up to {{cvt|5,000|kg}}. Other large pinnipeds include the [[northern elephant seal]] at {{cvt|4,000|kg}}, [[walrus]] at {{cvt|2,000|kg}}, and [[Steller sea lion]] at {{cvt|1,135|kg}}.<ref>{{Cite journal |last1=Churchill |first1=Morgan |last2=Clementz |first2=Mark T. |last3=Kohno |first3=Naoki |date=2014-12-19 |title=Cope's rule and the evolution of body size in Pinnipedimorpha (Mammalia: Carnivora) |url=|journal=Evolution |volume=69 |issue=1 |pages=201–215 |doi=10.1111/evo.12560 |pmid=25355195 |issn=0014-3820}}</ref><ref>{{Cite journal |last1=Haley |first1=Michael P. |last2=Deutsch |first2=Charles J. |last3=Boeuf |first3=Burney J. Le |date=April 1991 |title=A method for estimating mass of large pinnipeds |url=|journal=Marine Mammal Science |language=en |volume=7 |issue=2 |pages=157–164 |doi=10.1111/j.1748-7692.1991.tb00562.x |bibcode=1991MMamS...7..157H |issn=0824-0469}}</ref> The [[sirenia]]ns are another group of marine mammals which adapted to fully aquatic life around the same time as the cetaceans did. Sirenians are closely related to elephants. The largest sirenian was the [[Steller's sea cow]], which reached up to {{cvt|10|m}} in length and weighed {{cvt|8,000|to|10,000|kg}}, and was hunted to extinction in the 18th century.<ref>{{Cite journal |last=Goldbogen |first=J. A. |date=2018-04-17 |title=Physiological constraints on marine mammal body size |journal=Proceedings of the National Academy of Sciences |language=en |volume=115 |issue=16 |pages=3995–3997 |doi=10.1073/pnas.1804077115 |doi-access=free |issn=0027-8424 |pmc=5910879 |pmid=29618615|bibcode=2018PNAS..115.3995G }}</ref>

===In flightless birds===
[[File:Dinornithidae SIZE 01.png|thumb|A size comparison between a human and 4 [[moa]] species: {{Clear}} '''1.''' ''[[Dinornis novaezealandiae]]'' {{Clear}} '''2.''' ''[[Emeus crassus]]'' {{Clear}} '''3.''' ''[[Anomalopteryx didiformis]]'' {{Clear}} '''4.''' ''[[Dinornis robustus]]'']]
Because of the small initial size of all mammals following the extinction of the non-avian dinosaurs, nonmammalian vertebrates had a roughly ten-million-year-long window of opportunity (during the Paleocene) for evolution of gigantism without much competition.<ref name = "Mitchell2014">{{Cite journal| doi = 10.1126/science.1251981| pmid = 24855267| title = Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution| journal = Science| volume = 344| issue = 6186| pages = 898–900| date = 2014-05-23| last1 = Mitchell| first1 = K. J.| last2 = Llamas| first2 = B.| last3 = Soubrier| first3 = J.| last4 = Rawlence| first4 = N. J.| last5 = Worthy| first5 = T. H.| last6 = Wood| first6 = J.| last7 = Lee| first7 = M. S. Y.| last8 = Cooper| first8 = A.| bibcode = 2014Sci...344..898M| hdl = 2328/35953| s2cid = 206555952| url = https://dspace.flinders.edu.au/xmlui/bitstream/2328/35953/1/Mitchell_AncientDNA_AM2014.pdf| hdl-access = free| access-date = 2019-09-24| archive-date = 2023-03-15| archive-url = https://web.archive.org/web/20230315211934/https://dspace.flinders.edu.au/xmlui/bitstream/2328/35953/1/Mitchell_AncientDNA_AM2014.pdf| url-status = live}}</ref> During this interval, [[apex predator]] niches were often occupied by reptiles, such as terrestrial [[crocodilian]]s (e.g. ''[[Pristichampsus]]''), large snakes (e.g. ''[[Titanoboa]]'') or [[varanid lizard]]s, or by flightless birds<ref name = "F.A.Smith"/> (e.g. ''[[Paleopsilopterus]]'' in South America). This is also the period when megafaunal flightless herbivorous [[gastornithid]] birds evolved in the Northern Hemisphere, while flightless [[paleognath]]s evolved to large size on [[Gondwana]]n land masses and [[Europe]]. Gastornithids and at least one lineage of flightless paleognath birds originated in Europe, both lineages dominating niches for large herbivores while mammals remained below {{Convert|45|kg|lb}} (in contrast with other landmasses like [[North America]] and [[Asia]], which saw the earlier evolution of larger mammals) and were the largest European tetrapods in the [[Paleocene]].<ref name="Buffetaut2014">{{cite journal|last1=Buffetaut|first1=E.|last2=Angst|first2=D.|title=Stratigraphic distribution of large flightless birds in the Palaeogene of Europe and its palaeobiological and palaeogeographical implications|journal=Earth-Science Reviews|volume=138|date=November 2014|pages=394–408|doi=10.1016/j.earscirev.2014.07.001|bibcode=2014ESRv..138..394B}}</ref>

Flightless paleognaths, termed [[ratite]]s, have traditionally been viewed as representing a lineage separate from that of their small flighted relatives, the [[Neotropic]] [[tinamou]]s. However, recent genetic studies have found that tinamous nest well within the ratite tree, and are the [[sister group]] of the extinct [[moa]] of New Zealand.<ref name = "Mitchell2014" /><ref name = "Phillips2010">{{cite journal |vauthors=Phillips MJ, Gibb GC, Crimp EA, Penny D |title=Tinamous and moa flock together: mitochondrial genome sequence analysis reveals independent losses of flight among ratites |journal=Systematic Biology |volume=59 |issue=1 |pages=90–107 |date=January 2010  |pmid=20525622 |doi=10.1093/sysbio/syp079|doi-access=free }}</ref><ref name = "Baker2014">{{Cite journal | doi = 10.1093/molbev/msu153| title = Genomic Support for a Moa-Tinamou Clade and Adaptive Morphological Convergence in Flightless Ratites| journal = Molecular Biology and Evolution| year = 2014| last1 = Baker | first1 = A. J.| last2 = Haddrath | first2 = O.| last3 = McPherson | first3 = J. D.| last4 = Cloutier | first4 = A.| volume=31 | issue = 7| pages=1686–1696 | pmid=24825849| doi-access = free}}</ref> Similarly, the small [[Kiwi (bird)|kiwi]] of New Zealand have been found to be the sister group of the extinct [[elephant bird]]s of Madagascar.<ref name = "Mitchell2014" /> These findings indicate that [[Flightless bird|flightlessness]] and gigantism arose independently multiple times among ratites via [[parallel evolution]].<ref name="Murray 2004" />

Predatory megafaunal flightless birds were often able to compete with mammals in the early [[Cenozoic]]. Later in the Cenozoic, however, they were displaced by advanced carnivorans and died out. In North America, the [[bathornithids]] ''[[Paracrax]]'' and ''[[Bathornis]]'' were apex predators but became extinct by the [[Early Miocene]]. In South America, the related [[phorusrhacid]]s shared the dominant predatory niches with metatherian [[Sparassodonta|sparassodont]]s during most of the Cenozoic but declined and ultimately went extinct after eutherian predators arrived from North America (as part of the [[Great American Interchange]]) during the [[Pliocene]]. In contrast, large herbivorous flightless ratites have survived to the present.<ref name="Murray 2004" />

However, none of the flightless birds of the Cenozoic, including the predatory ''[[Brontornis]]'', possibly omnivorous ''[[Dromornis stirtoni]]''<ref name = "Murray 2004">{{cite book
  | last1 = Murray | first1 = Peter F.
  | last2 = Vickers-Rich | first2 = Patricia
  | year = 2004
  | title = Magnificent Mihirungs: The Colossal Flightless Birds of the Australian Dreamtime
  | url=https://books.google.com/books?id=-t6cQHdVEggC&pg=PA51
  | publisher = Indiana University Press | pages = 51, 314
  | isbn = 978-0-253-34282-9 | access-date=7 January 2012
}}</ref> or herbivorous ''[[Aepyornis]]'', ever grew to masses much above {{Convert|500|kg|lb}}, and thus never attained the size of the largest mammalian carnivores, let alone that of the largest mammalian herbivores. It has been suggested that the increasing thickness of avian eggshells in proportion to egg mass with increasing egg size places an upper limit on the size of birds.<ref name = "Murray 2004b">{{cite book
  | last1 = Ibid | url=https://books.google.com/books?id=-t6cQHdVEggC&pg=PA212
  | title = p. 212| isbn=978-0-253-34282-9
  | year=2004
  | publisher=Indiana University Press }}</ref>{{refn | Nonavian dinosaur size was not similarly constrained because they had a different relationship between body mass and egg size than birds. The {{Convert|400|kg|lb}} ''[[Aepyornis]]'' had larger eggs than nearly all dinosaurs.<ref name="Carpenter1999">{{cite book|author=Kenneth Carpenter|title=Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction|url=https://archive.org/details/isbn_9780253334978|url-access=registration|page=[https://archive.org/details/isbn_9780253334978/page/100 100]|access-date=6 May 2013|year=1999|publisher=[[Indiana University Press]]|isbn=978-0-253-33497-8|oclc= 42009424}}</ref><ref name="JacksonVarricchio2008">{{cite journal|last1=Jackson|first1=F. D.|last2= Varricchio|first2=D. J.|last3=Jackson|first3=R. A.|last4=Vila|first4= B.|last5=Chiappe |first5=L. M.|title=Comparison of water vapor conductance in a titanosaur egg from the Upper Cretaceous of Argentina and a ''Megaloolithus siruguei'' egg from Spain|journal=Paleobiology|volume= 34|issue=2|year=2008|pages= 229–246|issn=0094-8373|doi= 10.1666/0094-8373(2008)034[0229:COWVCI]2.0.CO;2|s2cid=85880201 }}</ref>| group = note}} The largest species of ''Dromornis'', ''D. stirtoni'', may have gone extinct after it attained the maximum avian body mass and was then outcompeted by marsupial [[diprotodon]]ts that evolved to sizes several times larger.<ref name = "Murray 2004c">{{cite book
  | last1 = Ibid | url=https://books.google.com/books?id=-t6cQHdVEggC&pg=PA277
  | title = p. 277| isbn=978-0-253-34282-9
  | year=2004
  | publisher=Indiana University Press }}</ref>

===In giant turtles===
[[Giant tortoise]]s were important components of late [[Cenozoic]] megafaunas, being present in every nonpolar continent until the arrival of [[hominina]]ns.<ref name="Hansen">{{Cite journal
 |last=Hansen
 |first=D. M.
 |author2=Donlan, C. J.
 |author3=Griffiths, C. J.
 |author4=Campbell, K. J.
 |title=Ecological history and latent conservation potential: large and giant tortoises as a model for taxon substitutions
 |journal=[[Ecography (journal)|Ecography]]
 |volume=33
 |issue=2
 |pages=272–284
 |date=April 2010
 |url=http://www.advancedconservation.org/library/hansen_etal_2010.pdf
 |doi=10.1111/j.1600-0587.2010.06305.x
 |bibcode=2010Ecogr..33..272H
 |access-date=2011-02-26
 |archive-url=https://web.archive.org/web/20110724224354/http://www.advancedconservation.org/library/hansen_etal_2010.pdf
 |archive-date=July 24, 2011
}}</ref><ref name="Cione">{{Cite journal
 |last=Cione
 |first=A. L.
 |author2=Tonni, E. P.
 |author3=Soibelzon, L.
 |title=The Broken Zig-Zag: Late Cenozoic large mammal and tortoise extinction in South America
 |journal=Rev. Mus. Argentino Cienc. Nat. |series=Nueva Serie
 |volume=5
 |issue=1
 |pages=1–19
 |year=2003
 |issn=1514-5158
 |doi= 10.22179/REVMACN.5.26
 |doi-access=free
 }}</ref> The largest known terrestrial tortoise was ''[[Megalochelys atlas]]'', an animal that probably weighed about {{cvt|1,000|kg}}.<ref>{{Citation |last1=Gordon |first1=Iain J. |title=The Ecology of Browsing and Grazing in Other Vertebrate Taxa |date=2019 |work=The Ecology of Browsing and Grazing II |pages=339–404 |editor-last=Gordon |editor-first=Iain J. |url=|place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-25865-8_15 |isbn=978-3-030-25865-8 |last2=Prins |first2=Herbert H. T. |last3=Mallon |first3=Jordan |last4=Puk |first4=Laura D. |last5=Miranda |first5=Everton B. P. |last6=Starling-Manne |first6=Carolina |last7=van der Wal |first7=René |last8=Moore |first8=Ben |last9=Foley |first9=William |editor2-last=Prins |editor2-first=Herbert H. T.}}</ref>

Some earlier aquatic Testudines, e.g. the marine ''[[Archelon]]'' of the Cretaceous<ref>{{Cite journal |last1=Jaffe |first1=Alexander L. |last2=Slater |first2=Graham J. |last3=Alfaro |first3=Michael E. |date=2011-08-23 |title=The evolution of island gigantism and body size variation in tortoises and turtles |journal=Biology Letters |language=en |volume=7 |issue=4 |pages=558–561 |doi=10.1098/rsbl.2010.1084 |issn=1744-9561 |pmc=3130210 |pmid=21270022}}</ref> and freshwater ''[[Stupendemys]]'' of the Miocene, were considerably larger, weighing more than {{cvt|2,000|kg}}.<ref>{{Cite journal |last1=Cadena |first1=Edwin-Alberto |last2=Link |first2=Andrés |last3=Cooke |first3=Siobhán B. |last4=Stroik |first4=Laura K. |last5=Vanegas |first5=Andrés F. |last6=Tallman |first6=Melissa |date=December 2021 |title=New insights on the anatomy and ontogeny of the largest extinct freshwater turtles |url=|journal=Heliyon |volume=7 |issue=12 |pages=e08591 |doi=10.1016/j.heliyon.2021.e08591 |doi-access=free |pmid=35005268 |pmc=8717240 |bibcode=2021Heliy...708591C |issn=2405-8440}}</ref>

==Megafaunal mass extinctions==

===Timing and possible causes===
{{Main|Late Pleistocene extinctions}}
[[File:Large Mammals Africa Australia NAmerica Madagascar.svg|thumb|upright=1.25|Correlations between times of first appearance of humans and unique megafaunal extinction pulses on different land masses]]
[[File:Ice Age Temperature.png|thumb|upright=1.25|Cyclical pattern of global [[Climate change (general concept)|climate change]] over the last 450,000 years (based on Antarctic temperatures and global ice volume), showing that there were no unique climatic events that would account for any of the megafaunal extinction pulses]]

[[Late Pleistocene extinctions|Numerous extinctions]] occurred during the latter half of the [[Last Glacial Period]] when most large mammals went extinct in the [[Americas]], [[Australia-New Guinea]], and [[Eurasia]], including over 80% of all terrestrial animals with a body mass greater than {{Convert|1,000|kg|lb}}. Small animals and other organisms like plants were generally unaffected by the extinctions, which is unprecented in previous extinctions during the last 30 million years.<ref name=":2">{{Cite journal |last1=Svenning |first1=Jens-Christian |last2=Lemoine |first2=Rhys T. |last3=Bergman |first3=Juraj |last4=Buitenwerf |first4=Robert |last5=Le Roux |first5=Elizabeth |last6=Lundgren |first6=Erick |last7=Mungi |first7=Ninad |last8=Pedersen |first8=Rasmus Ø. |date=2024 |title=The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene |journal=Cambridge Prisms: Extinction |language=en |volume=2 |doi=10.1017/ext.2024.4 |issn=2755-0958 |doi-access=free|pmc=11895740 }}</ref>

Various theories have attributed the wave of extinctions to [[Quaternary extinction event#Hunting hypothesis|human hunting]], [[Quaternary extinction event#Climate change hypothesis|climate change]], [[Quaternary extinction event#Hyperdisease hypothesis|disease]], [[Younger Dryas impact event|extraterrestrial impact]], [[Competition (biology)|competition from other animals]] or other causes. However, this extinction near the end of the [[Pleistocene]] was just one of a series of megafaunal extinction pulses that have occurred during the last 50,000 years over much of the Earth's surface, with [[Africa]] and [[Asia]] (where the local megafauna had a chance to evolve alongside modern humans) being comparatively less affected. The latter areas did suffer gradual attrition of megafauna, particularly of the slower-moving species (a class of vulnerable megafauna epitomized by [[giant tortoise]]s), over the last several million years.<ref name="corlett">{{Cite journal | last1 = Corlett | first1 = R. T. | year = 2006 | title = Megafaunal extinctions in tropical Asia | url = http://www.tropicalbio.org/pastissues/tn_v17_n3_Sept_2006.pdf | journal = Tropinet | volume = 17 | issue = 3 | pages = 1–3 | access-date = 2010-10-04 | archive-date = 2016-03-04 | archive-url = https://web.archive.org/web/20160304074435/http://www.tropicalbio.org/pastissues/tn_v17_n3_Sept_2006.pdf | url-status = live }}</ref><ref name="Edmeades">{{Cite web | last = Edmeades | first = Baz | title = Megafauna — First Victims of the Human-Caused Extinction | website= megafauna.com |publisher = (internet-published book with Foreword by [[Paul Schultz Martin|Paul S. Martin]]) | url = http://www.megafauna.com/ | access-date = 2020-02-13 | archive-url = https://web.archive.org/web/20141225044106/http://megafauna.com/table-of-contents/ | archive-date = 2014-12-25  }}</ref>

Outside the mainland of [[Afro-Eurasia]], these megafaunal extinctions followed a highly distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world, and which shows no overall correlation with climatic history (which can be visualized with plots over recent geological time periods of climate markers such as [[:Image:Five Myr Climate Change.png|marine oxygen isotopes]] or [[:Image:Atmospheric CO2 with glaciers cycles.gif|atmospheric carbon dioxide levels]]).<ref name="Martin">{{cite book | last = Martin | first = P. S. | author-link = Paul Schultz Martin | title = Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America | publisher = [[University of California Press]] | year = 2005 | chapter = Chapter 6. Deadly Syncopation | pages = 118–128 | url = https://books.google.com/books?id=gfpla1OY268C | chapter-url = https://books.google.com/books?id=gfpla1OY268C&pg=PA118 | isbn = 978-0-520-23141-2 | oclc = 58055404 | access-date = 2014-11-11 | archive-date = 2024-03-27 | archive-url = https://web.archive.org/web/20240327192513/https://books.google.com/books?id=gfpla1OY268C | url-status = live }}</ref><ref name="Burney">{{Cite journal
 | last1 = Burney | first1 = D. A. 
 | last2=Flannery | first2 = T. F. | author-link2 = Tim Flannery
 | title = Fifty millennia of catastrophic extinctions after human contact
 | journal = Trends in Ecology & Evolution | volume = 20 | issue = 7 | pages = 395–401 | date = July 2005
 | url = http://web.njit.edu/~krussell/Required.pdf
 | doi = 10.1016/j.tree.2005.04.022 | pmid = 16701402 | access-date = 2014-11-11 
 | archive-url= https://web.archive.org/web/20100610061434/http://www.anthropology.hawaii.edu/Fieldschools/Kauai/Publications/Publication%204.pdf
 | archive-date= 2010-06-10 }}</ref> [[Australia]]<ref name="New Ages">{{Cite journal | last1 = Roberts | first1 = R. G. | last2 = Flannery | first2 = T. F. | author2-link = Tim Flannery | last3 = Ayliffe | first3 = L. K. | last4 = Yoshida | first4 = H. | last5 = Olley | first5 = J. M. | last6 = Prideaux | first6 = G. J. | last7 = Laslett | first7 = G. M. | last8 = Baynes | first8 = A. | last9 = Smith | first9 = M. A. | last10 = Jones | first10 = R. | last11 = Smith | first11 = B. L. | title = New Ages for the Last Australian Megafauna: Continent-Wide Extinction About 46,000 Years Ago | journal = [[Science (journal)|Science]] | volume = 292 | issue = 5523 | pages = 1888–1892 | date = 2001-06-08 | url = http://www.uow.edu.au/content/groups/public/@web/@sci/@eesc/documents/doc/uow014698.pdf | doi = 10.1126/science.1060264 | access-date = 2011-08-26 | pmid = 11397939 | bibcode = 2001Sci...292.1888R | s2cid = 45643228 | archive-date = 2019-02-10 | archive-url = https://web.archive.org/web/20190210051502/https://www.uow.edu.au/content/groups/public/@web/@sci/@eesc/documents/doc/uow014698.pdf | url-status = live }}</ref> and nearby islands (e.g., [[Flores]]<ref name="Callaway2016">{{cite journal
 |last1= Callaway|first1= E.|title=Human remains found in hobbit cave|journal= Nature|date= 2016-09-21|doi= 10.1038/nature.2016.20656|s2cid= 89272546}}</ref>) were struck first around 46,000 years ago, followed by [[Tasmania]] about 41,000 years ago (after formation of a land bridge to Australia about 43,000 years ago).<ref name="Diamond">{{Cite journal
 | last = Diamond | first = Jared | author-link = Jared Diamond | title = Palaeontology: The last giant kangaroo
 | journal = [[Nature (journal)|Nature]] | volume = 454 | issue = 7206 |pages = 835–836 | date = 2008-08-13 | doi = 10.1038/454835a | pmid=18704074|bibcode = 2008Natur.454..835D| s2cid = 36583693 }}</ref><ref name="Turney">{{Cite journal
 | last1=Turney|first1=C. S. M.|last2=Flannery|first2=T. F.|last3=Roberts|first3=R. G.|last4=Reid|first4=C.|last5=Fifield|first5=L. K.|last6=Higham|first6=T. F. G.|last7=Jacobs|first7=Z.|last8=Kemp|first8=N.|last9=Colhoun|first9=E. A.|last10=Kalin|first10=R. M.|last11=Ogle|first11=N. | author-link2 =Tim Flannery | title = Late-surviving megafauna in Tasmania, Australia, implicate human involvement in their extinction | journal = [[Proceedings of the National Academy of Sciences|PNAS]] | volume = 105 | issue = 34 | pages = 12150–12153 | date = 2008-08-21 | doi = 10.1073/pnas.0801360105 | pmid=18719103 | pmc=2527880|bibcode = 2008PNAS..10512150T|doi-access=free}}</ref><ref name="Lost Giants">{{Cite journal
 |last=Roberts
 |first=R.
 |author2=Jacobs, Z.
 |title=The Lost Giants of Tasmania
 |journal=[[Australasian Science]]
 |volume=29
 |issue=9
 |pages=14–17
 |date=October 2008
 |url=http://www.control.com.au/bi2008/299megafauna.pdf
 |access-date=2011-08-26
 |archive-url=https://web.archive.org/web/20110927111457/http://www.control.com.au/bi2008/299megafauna.pdf
 |archive-date=2011-09-27
}}</ref> The role of humans in the extinction of Australia and New Guinea's megafauna has been disputed, with multiple studies showing a decline in the number of species prior to the arrival of humans on the continent and the absence of any evidence of human predation;<ref name=":0">{{Cite journal|last1=Field|first1=Judith|last2=Wroe|first2=Stephen|last3=Trueman|first3=Clive N.|last4=Garvey|first4=Jillian|last5=Wyatt-Spratt|first5=Simon|date=2013-02-08|title=Looking for the archaeological signature in Australian Megafaunal extinctions|url=http://www.sciencedirect.com/science/article/pii/S1040618211002266|journal=Quaternary International|series=Peopling the last new worlds: the first colonisation of Sahul and the Americas|language=en|volume=285|pages=76–88|doi=10.1016/j.quaint.2011.04.013|bibcode=2013QuInt.285...76F|issn=1040-6182|archive-date=2012-12-18|archive-url=https://web.archive.org/web/20121218072629/http://www.sciencedirect.com/science/article/pii/S1040618211002266|url-status=live}}</ref><ref>{{Cite journal|last1=Dodson|first1=John|last2=Field|first2=Judith H.|date=2018|title=What does the occurrence of Sporormiella (Preussia) spores mean in Australian fossil sequences?|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/jqs.3020|journal=Journal of Quaternary Science|language=en|volume=33|issue=4|pages=380–392|doi=10.1002/jqs.3020|bibcode=2018JQS....33..380D|s2cid=133737405|issn=1099-1417|archive-date=2022-02-14|archive-url=https://web.archive.org/web/20220214002000/https://onlinelibrary.wiley.com/doi/abs/10.1002/jqs.3020|url-status=live}}</ref><ref>{{Cite journal|last1=Wroe|first1=Stephen|last2=Field|first2=Judith H.|last3=Archer|first3=Michael|last4=Grayson|first4=Donald K.|last5=Price|first5=Gilbert J.|last6=Louys|first6=Julien|last7=Faith|first7=J. Tyler|last8=Webb|first8=Gregory E.|last9=Davidson|first9=Iain|last10=Mooney|first10=Scott D.|date=2013-09-03|title=Reply to Brook et al: No empirical evidence for human overkill of megafauna in Sahul|journal=Proceedings of the National Academy of Sciences|language=en|volume=110|issue=36|pages=E3369|doi=10.1073/pnas.1310440110|issn=0027-8424|pmid=24137797|pmc=3767508|bibcode=2013PNAS..110E3369W |doi-access=free}}</ref><ref>{{Cite journal|last1=Dortch|first1=Joe|last2=Cupper|first2=Matt|last3=Grün|first3=Rainer|last4=Harpley|first4=Bernice|last5=Lee|first5=Kerrie|last6=Field|first6=Judith|date=2016-08-01|title=The timing and cause of megafauna mass deaths at Lancefield Swamp, south-eastern Australia|url=https://www.sciencedirect.com/science/article/abs/pii/S0277379116301949|journal=Quaternary Science Reviews|language=en|volume=145|pages=161–182|doi=10.1016/j.quascirev.2016.05.042|bibcode=2016QSRv..145..161D|issn=0277-3791|archive-date=2024-03-27|archive-url=https://web.archive.org/web/20240327192636/https://www.sciencedirect.com/science/article/abs/pii/S0277379116301949|url-status=live}}</ref> the impact of climate change has instead been cited for their decline.<ref>{{Cite journal|last1=Wroe|first1=Stephen|last2=Field|first2=Judith H.|last3=Archer|first3=Michael|last4=Grayson|first4=Donald K.|last5=Price|first5=Gilbert J.|last6=Louys|first6=Julien|last7=Faith|first7=J. Tyler|last8=Webb|first8=Gregory E.|last9=Davidson|first9=Iain|last10=Mooney|first10=Scott D.|date=2013-05-28|title=Climate change frames debate over the extinction of megafauna in Sahul (Pleistocene Australia-New Guinea)|journal=Proceedings of the National Academy of Sciences|language=en|volume=110|issue=22|pages=8777–8781|doi=10.1073/pnas.1302698110|issn=0027-8424|pmid=23650401|pmc=3670326|bibcode=2013PNAS..110.8777W |doi-access=free}}</ref><ref name=":0" /> Similarly, [[Japan]] lost most of its megafauna apparently about 30,000 years ago,<ref name="Norton">{{Cite journal
 | last = Norton | first = C. J. |author2=Kondo, Y. |author3=Ono, A. |author4=Zhang, Y. |author5=Diab, M. C.
 | title = The nature of megafaunal extinctions during the MIS 3–2 transition in Japan
 | journal = [[Quaternary International]] | volume = 211 | issue = 1–2 | pages = 113–122
 | date = 2009-05-23 | doi = 10.1016/j.quaint.2009.05.002
 |bibcode = 2010QuInt.211..113N}}</ref> [[North America]] 13,000 years ago{{refn | Analysis indicates that 35 genera of North American mammals went extinct more or less simultaneously in this event.<ref name="Faith2009">{{cite journal|last1=Faith|first1=J. T.|last2=Surovell|first2=T. A.|title=Synchronous extinction of North America's Pleistocene mammals|journal= Proceedings of the National Academy of Sciences|volume= 106|issue= 49|date= 2009-12-08|pages= 20641–20645|doi=10.1073/pnas.0908153106|pmid=19934040|pmc=2791611|bibcode=2009PNAS..10620641F|doi-access=free}}</ref>| group = note}} and [[South America]] about 500 years later,<ref name="Haynes">{{Cite book | first = Gary | last = Haynes | editor-last = Haynes | editor-first = Gary | contribution = Introduction to the Volume | contribution-url = http://www.springerlink.com/content/w314m76738r91g35/?p=5af1eb7387d443a2b514b284c646efa7&pi=0 | title = American Megafaunal Extinctions at the End of the Pleistocene | year = 2009 | pages = 1–20 | publisher = [[Springer Science+Business Media|Springer]] | doi = 10.1007/978-1-4020-8793-6_1 | isbn = 978-1-4020-8792-9 | series = Vertebrate Paleobiology and Paleoanthropology }}{{Dead link|date=September 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="Fiedel">{{Cite book
 | first = Stuart | last = Fiedel | editor-last = Haynes | editor-first = Gary
 | contribution = Sudden Deaths: The Chronology of Terminal Pleistocene Megafaunal Extinction
 | title = American Megafaunal Extinctions at the End of the Pleistocene | year = 2009 | pages = 21–37
 | publisher = [[Springer Science+Business Media|Springer]]
 | doi = 10.1007/978-1-4020-8793-6_2 | isbn = 978-1-4020-8792-9| series = Vertebrate Paleobiology and Paleoanthropology }}</ref> [[Prehistoric Cyprus|Cyprus]] 10,000 years ago,<ref name="Simmons1">{{Cite book | last = Simmons | first = A. H. | title = Faunal extinction in an island society: pygmy hippopotamus hunters of Cyprus | publisher = [[Kluwer Academic/Plenum Publishers]] | series = Interdisciplinary Contributions to Archaeology | year = 1999 | page = 382 | url = https://books.google.com/books?id=hCwYwyEBXEAC | doi = 10.1007/b109876 | isbn = 978-0-306-46088-3 | oclc = 41712246 | access-date = 2016-05-07 | archive-date = 2024-03-27 | archive-url = https://web.archive.org/web/20240327192513/https://books.google.com/books?id=hCwYwyEBXEAC | url-status = live }}</ref><ref name="Simmons2">{{Cite journal
 | last = Simmons | first = A. H. |author2=Mandel, R. D.
 | title = Not Such a New Light: A Response to Ammerman and Noller | journal = [[World Archaeology]]
 | volume = 39 | issue = 4 | pages = 475–482 | date = December 2007
 | jstor = 40026143
 | doi = 10.1080/00438240701676169| s2cid = 161791746 }}</ref> the [[Antilles]] 6,000 years ago,<ref name="Steadman">{{cite journal
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 | last4 = Jull | first4 = A. J. T.
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 | last6 = Woods | first6 = C. A.
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 | last8 = Hodgins | first8 = G. W. L.
 | title = Asynchronous extinction of late Quaternary sloths on continents and islands
 | journal = [[Proceedings of the National Academy of Sciences|Proc. Natl. Acad. Sci. USA]]
 | volume = 102 | issue = 33 | pages = 11763–11768
 | date = 2005-08-16 |doi = 10.1073/pnas.0502777102 |pmid = 16085711
 | pmc = 1187974|bibcode = 2005PNAS..10211763S| doi-access = free }}</ref><ref name="Cooke2017">{{cite journal|last1= Cooke|first1=S. B.|last2= Dávalos|first2=L. M.|last3= Mychajliw|first3=A. M.|last4= Turvey|first4=S. T.|last5= Upham|first5=N. S.|title= Anthropogenic Extinction Dominates Holocene Declines of West Indian Mammals|journal= Annual Review of Ecology, Evolution, and Systematics|volume= 48|issue= 1|year= 2017|pages= 301–327|doi= 10.1146/annurev-ecolsys-110316-022754|s2cid=90558542 }}</ref> [[New Caledonia#Ecology|New Caledonia]]<ref name="Anderson">{{Cite journal
 | last = Anderson | first = A. |author2=Sand, C. |author3=Petchey, F. |author4=Worthy, T. H.
 | title = Faunal extinction and human habitation in New Caledonia: Initial results and implications of new research at the Pindai Caves
 | journal = Journal of Pacific Archaeology | volume = 1 | issue = 1 | pages = 89–109
 | year = 2010 | hdl = 10289/5404
 }}</ref> and nearby islands<ref name="White">{{Cite journal
 | last = White | first = A. W. |author2=Worthy, T. H. |author3=Hawkins, S. |author4=Bedford, S. |author5=Spriggs, M.
 | title = Megafaunal meiolaniid horned turtles survived until early human settlement in Vanuatu, Southwest Pacific
 | journal = [[PNAS|Proc. Natl. Acad. Sci. USA]]
 | volume = 107 | issue = 35 | pages = 15512–15516
 | date = 2010-08-16 |doi = 10.1073/pnas.1005780107|bibcode = 2010PNAS..10715512W | pmid=20713711 | pmc=2932593| doi-access = free }}</ref> 3,000 years ago, [[Madagascar]] 2,000 years ago,<ref name="Madagascar">{{Cite journal
 | last = Burney | first = D. A. 
 |author2=Burney, L. P. |author3=Godfrey, L. R. |author4=Jungers, W. L. |author5=Goodman, S. M. |author6=Wright, H. T. |author7= Jull. A. J. T.
 | title = A chronology for late prehistoric Madagascar
 | journal = [[Journal of Human Evolution]] | volume = 47 | issue = 1–2 | pages = 25–63
 | date = July 2004 | doi = 10.1016/j.jhevol.2004.05.005 | pmid=15288523}}</ref> [[New Zealand]] 700 years ago,<ref name="Holdaway">{{cite journal
 | last = Holdaway | first = R. N. |author2=Jacomb, C.
 | date = 2000-03-24 | title = Rapid Extinction of the Moas (Aves: Dinornithiformes): Model, Test, and Implications
 | journal = [[Science (journal)|Science]] | volume = 287 | issue = 5461 | pages = 2250–2254
 | doi = 10.1126/science.287.5461.2250 | pmid = 10731144 |bibcode = 2000Sci...287.2250H}}</ref> the [[Mascarene Islands|Mascarenes]] 400 years ago,<ref name="Janoo">{{Cite journal
 | last = Janoo | first = A. | title = Discovery of isolated dodo bones (''Raphus cucullatus'' (L.), Aves, Columbiformes) from Mauritius cave shelters highlights human predation, with a comment on the status of the family Raphidae Wetmore, 1930
 | journal = Annales de Paléontologie | volume = 91 | issue = 2 | pages = 167–180
 | date = April 2005 | doi = 10.1016/j.annpal.2004.12.002
 | bibcode = 2005AnPal..91..167J }}</ref> and the [[Commander Islands]] 250 years ago.<ref name="Hydrodamalis">{{cite journal
 | last = Anderson | first = P. K. | title = Competition, Predation, and the Evolution and Extinction of Steller's Sea Cow, ''Hydrodamalis gigas''
 | journal = Marine Mammal Science | volume = 11 | issue = 3 | pages = 391–394
 | date = July 1995 | url = http://www3.interscience.wiley.com/journal/119963340/abstract
 | archive-url = https://archive.today/20110511193530/http://www3.interscience.wiley.com/journal/119963340/abstract
 | archive-date = 2011-05-11
 | doi = 10.1111/j.1748-7692.1995.tb00294.x
 | bibcode = 1995MMamS..11..391A | access-date = 2011-08-30}}</ref> Nearly all of the world's isolated islands could furnish similar examples of extinctions occurring shortly after the arrival of [[human]]s, though most of these islands, such as the [[Hawaiian Islands]], never had terrestrial megafauna, so their [[List of extinct animals of the Hawaiian Islands|extinct fauna]] were smaller, but still displayed [[island gigantism]].<ref name="Martin"/><ref name="Burney"/>

An analysis of the timing of [[Holarctic]] megafaunal extinctions and extirpations over the last 56,000 years has revealed a tendency for such events to cluster within [[interstadial]]s, periods of abrupt warming, but only when humans were also present. Humans may have impeded processes of migration and recolonization that would otherwise have allowed the megafaunal species to adapt to the climate shift.<ref name="Cooper2015">{{cite journal|last1=Cooper|first1=A.|last2=Turney|first2=C.|last3=Hughen|first3=K. A.|last4=Brook|first4=B. W.|last5=McDonald|first5=H. G.|last6=Bradshaw|first6=C. J. A.|title=Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover|journal=Science|date=2015-07-23|doi=10.1126/science.aac4315|pmid=26250679|volume=349|issue=6248|pages=602–6|bibcode=2015Sci...349..602C|s2cid=31686497|doi-access=free}}</ref> In at least some areas, interstadials were periods of expanding human populations.<ref name="Müller2011">{{cite journal|last1=Müller|first1=U. C.|last2=Pross|first2=J.|last3=Tzedakis|first3=P. C.|last4=Gamble|first4=C.|last5=Kotthoff|first5=U.|last6=Schmiedl|first6=G.|last7=Wulf|first7=S.|last8=Christanis|first8=K.|title=The role of climate in the spread of modern humans into Europe|journal=[[Quaternary Science Reviews]]|volume= 30|issue= 3–4|date= February 2011|pages= 273–279|doi= 10.1016/j.quascirev.2010.11.016|bibcode=2011QSRv...30..273M}}</ref>

An analysis of ''[[Sporormiella]]'' fungal spores (which derive mainly from the dung of megaherbivores) in swamp sediment cores spanning the last 130,000 years from [[Lynch's Crater]] in [[Queensland]], Australia, showed that the megafauna of that region virtually disappeared about 41,000 years ago, at a time when [[Climate change (general concept)|climate change]]s were minimal; the change was accompanied by an increase in charcoal, and was followed by a transition from rainforest to fire-tolerant [[sclerophyll]] vegetation. The high-resolution chronology of the changes supports the hypothesis that human hunting alone eliminated the megafauna, and that the subsequent change in flora was most likely a consequence of the elimination of browsers and an increase in fire.<ref name="Biello">{{cite web
 | last = Biello
 | first = D.
 | title = Big Kill, Not Big Chill, Finished Off Giant Kangaroos
 | work = Scientific American news
 | date = 2012-03-22
 | url = http://www.scientificamerican.com/article.cfm?id=hunters-killed-off-big-animals-australia
 | access-date = 2012-03-25
 | archive-date = 2012-03-23
 | archive-url = https://web.archive.org/web/20120323062901/http://www.scientificamerican.com/article.cfm?id=hunters-killed-off-big-animals-australia
 | url-status = live
 }}</ref><ref name="McGlone">{{cite journal
 | last = McGlone | first = M. | title = The Hunters Did It
 | journal = [[Science (journal)|Science]]
 | volume = 335 | issue = 6075 | pages = 1452–1453
 | date = 2012-03-23 | doi = 10.1126/science.1220176 | pmid = 22442471 
 |bibcode = 2012Sci...335.1452M| s2cid = 36914192 }}</ref><ref name="Rule">{{cite journal
 | last = Rule | first = S. |author2=Brook, B. W. |author3=Haberle, S. G. |author4=Turney, C. S. M. |author5=Kershaw, A. P.
 | title = The Aftermath of Megafaunal Extinction: Ecosystem Transformation in Pleistocene Australia
 | journal = [[Science (journal)|Science]]
 | volume = 335 | issue = 6075 | pages = 1483–1486
 | date = 2012-03-23 | doi = 10.1126/science.1214261
 |bibcode = 2012Sci...335.1483R | pmid=22442481| s2cid = 26675232 }}</ref><ref name="Johnson2016"/> The increase in fire lagged the disappearance of megafauna by about a century, and most likely resulted from accumulation of fuel once browsing stopped. Over the next several centuries grass increased; sclerophyll vegetation increased with a lag of another century, and a sclerophyll forest developed after about another thousand years.<ref name="Rule"/> During two periods of climate change about 120,000 and 75,000 years ago, sclerophyll vegetation had also increased at the site in response to a shift to cooler, drier conditions; neither of these episodes had a significant impact on megafaunal abundance.<ref name="Rule"/> Similar conclusions regarding the culpability of human hunters in the disappearance of Pleistocene megafauna were derived from high-resolution chronologies obtained via an analysis of a large collection of eggshell fragments of the flightless Australian bird ''[[Genyornis newtoni]]'',<ref name="Miller1999">{{Cite journal | doi = 10.1126/science.283.5399.205 |pmid = 9880249 |title = Pleistocene Extinction of ''Genyornis newtoni'': Human Impact on Australian Megafauna |journal = Science |volume = 283 |issue = 5399 |pages = 205–208 |date = 1999-01-08 |last1 = Miller | first1 = G. H. |last2 = Magee |first2 = J. W. |last3 = Johnson |first3 = B. J. |last4 = Fogel |first4 = M. L. |last5 = Spooner |first5 = N. A. |last6 = McCulloch |first6 = M. T. |last7 = Ayliffe |first7 = L. K.}}</ref><ref name="MillerMagee2016">{{cite journal|last1=Miller|first1=G.|last2= Magee|first2=J.|last3= Smith|first3=M.|last4= Spooner|first4=N.|last5= Baynes|first5=A.|last6= Lehman|first6=S.|last7=Fogel|first7=M.|last8= Johnston|first8=H.|last9= Williams|first9=D.|last10= Clark|first10=P.|last11= Florian|first11=C.|last12= Holst|first12=R.|last13= DeVogel|first13=S.|title=Human predation contributed to the extinction of the Australian megafaunal bird Genyornis newtoni ~47 ka|journal=Nature Communications|volume= 7|date=2016-01-29|page= 10496|doi=10.1038/ncomms10496|pmid=26823193|pmc=4740177|bibcode=2016NatCo...710496M}}</ref><ref name="Johnson2016">{{cite journal | last1= Johnson|first1=C. N.|last2= Alroy|first2= J.|last3= Beeton|first3=N. J.|last4= Bird|first4=M. I.|last5= Brook|first5=B. W.|last6= Cooper|first6= A.|last7= Gillespie|first7= R.|last8= Herrando-Pérez|first8= S.|last9= Jacobs|first9= Z.|last10= Miller|first10=G. H.|last11= Prideaux|first11=G. J.|last12= Roberts|first12=R. G.|last13= Rodríguez-Rey|first13= M.|last14= Saltré|first14= F.|last15= Turney|first15=C. S. M.|last16= Bradshaw|first16=C. J. A. | title= What caused extinction of the Pleistocene megafauna of Sahul? | journal= Proceedings of the Royal Society B: Biological Sciences | volume= 283 | issue= 1824 | page= 20152399 | date= 10 February 2016 | doi= 10.1098/rspb.2015.2399|pmid=26865301|pmc=4760161}}</ref> from analysis of ''Sporormiella'' fungal spores from a lake in eastern North America<ref name="Johnson2009">{{Cite journal | doi = 10.1126/science.1182770 |pmid = 19965418 |title = Megafaunal Decline and Fall |journal = Science |volume = 326 |issue = 5956 |pages = 1072–1073 |date = 2009-11-20 |last1 = Johnson | first1 = C.|bibcode = 2009Sci...326.1072J |s2cid = 206523763 }}</ref><ref name="Gill2009">{{Cite journal |doi = 10.1126/science.1179504 |pmid = 19965426 |title = Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America |journal = Science |volume = 326 |issue = 5956 |pages = 1100–1103 |date = 2009-11-20 |last1 = Gill |first1 = J. L. |last2 = Williams |first2 = J. W. |last3 = Jackson |first3 = S. T. |last4 = Lininger |first4 = K. B. |last5 = Robinson |first5 = G. S. |bibcode = 2009Sci...326.1100G |s2cid = 206522597 |url = http://doc.rero.ch/record/210391/files/PAL_E4398.pdf |access-date = 2018-11-09 |archive-date = 2017-09-22 |archive-url = https://web.archive.org/web/20170922021056/http://doc.rero.ch/record/210391/files/PAL_E4398.pdf |url-status = live }}</ref> and from study of deposits of [[Shasta ground sloth]] dung left in over half a dozen caves in the American Southwest.<ref name = "Fiedal2009">{{Cite book | first = Stuart | last = Fiedal | editor-last = Haynes | editor-first = Gary | contribution = Sudden Deaths: The Chronology of Terminal Pleistocene Megafaunal Extinction | title = American Megafaunal Extinctions at the End of the Pleistocene | year = 2009 | pages = 21–37 | publisher = [[Springer Science+Business Media|Springer]] | doi = 10.1007/978-1-4020-8793-6_2 | isbn = 978-1-4020-8792-9 | series = Vertebrate Paleobiology and Paleoanthropology }}</ref><ref name="Martin2005b">{{cite book | last = Martin | first = P. S. | author-link = Paul Schultz Martin | title = Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America | publisher = [[University of California Press]] | year = 2005 | chapter = Chapter 4. Ground Sloths at Home | pages = 78–99 | url = https://books.google.com/books?id=gfpla1OY268C | chapter-url = https://books.google.com/books?id=gfpla1OY268C&pg=PA78 | isbn = 978-0-520-23141-2 | oclc = 58055404 | access-date = 2014-11-11 | archive-date = 2024-03-27 | archive-url = https://web.archive.org/web/20240327192513/https://books.google.com/books?id=gfpla1OY268C | url-status = live }}</ref>

Continuing human hunting and environmental disturbance has led to additional [[Holocene extinction#Ongoing Holocene extinction|megafaunal extinctions in the recent past]], and has created a [[IUCN Red List critically endangered species|serious danger of further extinctions]] in the near future (see examples below). Direct killing by humans, primarily for meat or other body parts, is the most significant factor in contemporary megafaunal decline.<ref>{{cite news|last=Milman|first=Oliver|date=February 6, 2019|title=The killing of large species is pushing them towards extinction, study finds|url=https://www.theguardian.com/world/2019/feb/06/the-killing-of-large-species-is-pushing-them-towards-extinction-study-finds|work=The Guardian|access-date=February 13, 2019|archive-date=February 7, 2019|archive-url=https://web.archive.org/web/20190207231757/https://www.theguardian.com/world/2019/feb/06/the-killing-of-large-species-is-pushing-them-towards-extinction-study-finds|url-status=live}}</ref><ref>{{cite journal|first=W. J.|last=Ripple|display-authors=etal.|year=2019|title=Are we eating the world's megafauna to extinction?|journal=Conservation Letters|volume=12|issue=3|page=e12627|doi=10.1111/conl.12627|doi-access=free|bibcode=2019ConL...12E2627R }}</ref>

A number of other [[Extinction event|mass extinction]]s occurred earlier in Earth's geologic history, in which some or all of the megafauna of the time also died out. Famously, in the [[Cretaceous–Paleogene extinction event]], the non-avian dinosaurs and most other giant reptiles were eliminated. However, the earlier mass extinctions were more global and not so selective for megafauna; i.e., many species of other types, including plants, marine invertebrates<ref name="Alroy">{{Cite journal
 | last = Alroy | first = J. | title = Dynamics of origination and extinction in the marine fossil record
 | journal = [[Proceedings of the National Academy of Sciences of the United States of America|PNAS]]
 | volume = 105 Suppl 1 | pages = 11536–11542 | date = 2008-08-12 | pmid = 18695240
 | pmc = 2556405 | doi = 10.1073/pnas.0802597105 |bibcode = 2008PNAS..10511536A
 | issue = Supplement_1| doi-access = free }}</ref> and plankton, went extinct as well. Thus, the earlier events must have been caused by more generalized types of disturbances to the [[biosphere]].<ref>{{Cite journal |last=D'Hondt |first=Steven |date=2005-12-01 |title=Consequences of the Cretaceous/Paleogene Mass Extinction for Marine Ecosystems |url=https://www.annualreviews.org/doi/10.1146/annurev.ecolsys.35.021103.105715 |journal=Annual Review of Ecology, Evolution, and Systematics |language=en |volume=36 |issue=1 |pages=295–317 |doi=10.1146/annurev.ecolsys.35.021103.105715 |issn=1543-592X}}</ref>

===Consequences of depletion of megafauna===
Depletion of herbivorous megafauna results in increased growth of woody vegetation,<ref name=":3">{{Cite journal |last1=Malhi |first1=Yadvinder |last2=Doughty |first2=Christopher E. |last3=Galetti |first3=Mauro |last4=Smith |first4=Felisa A. |last5=Svenning |first5=Jens-Christian |last6=Terborgh |first6=John W. |date=2016-01-26 |title=Megafauna and ecosystem function from the Pleistocene to the Anthropocene |journal=Proceedings of the National Academy of Sciences |language=en |volume=113 |issue=4 |pages=838–846 |doi=10.1073/pnas.1502540113 |doi-access=free |issn=0027-8424 |pmc=4743772 |pmid=26811442}}</ref> and a consequent increase in [[wildfire]] frequency.<ref>{{Cite journal |last=Johnson |first=C.N. |date=2009-07-22 |title=Ecological consequences of Late Quaternary extinctions of megafauna |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=276 |issue=1667 |pages=2509–2519 |doi=10.1098/rspb.2008.1921 |issn=0962-8452 |pmc=2684593 |pmid=19324773}}</ref> Megafauna may help to suppress the growth of invasive plants.<ref>{{Cite journal |last1=Mungi |first1=Ninad Avinash |last2=Jhala |first2=Yadvendradev V. |last3=Qureshi |first3=Qamar |last4=le Roux |first4=Elizabeth |last5=Svenning |first5=Jens-Christian |date=October 2023 |title=Megaherbivores provide biotic resistance against alien plant dominance |url=https://www.nature.com/articles/s41559-023-02181-y |journal=Nature Ecology & Evolution |language=en |volume=7 |issue=10 |pages=1645–1653 |doi=10.1038/s41559-023-02181-y |issn=2397-334X}}</ref> Large herbivores and carnivores can suppress the abundance of smaller animals, resulting in their population increase when megafauna are removed.<ref name=":3" /> 

==== Effect on nutrient transport ====
Megafauna play a significant role in the lateral transport of mineral nutrients in an ecosystem, tending to translocate them from areas of high to those of lower abundance. They do so by their movement between the time they consume the nutrient and the time they release it through elimination (or, to a much lesser extent, through decomposition after death).<ref name="Wolf2013">{{cite journal|last1=Wolf|first1=A.|last2=Doughty|first2=C. E.|last3=Malhi|first3=Y.|author-link3=Yadvinder Malhi|title=Lateral Diffusion of Nutrients by Mammalian Herbivores in Terrestrial Ecosystems|journal=[[PLoS ONE]]|volume= 8|issue= 8|year= 2013|pages= e71352|doi= 10.1371/journal.pone.0071352|pmid=23951141|pmc=3739793|bibcode=2013PLoSO...871352W|doi-access=free}}</ref> In South America's [[Amazon Basin]], it is estimated that such lateral diffusion was reduced over 98% following the megafaunal extinctions that occurred roughly 12,500 years ago.<ref name = "Marshall_2013">{{cite magazine | last = Marshall | first = M. | title = Ecosystems still feel the pain of ancient extinctions | magazine = [[New Scientist]] | date = 2013-08-11 | url = https://www.newscientist.com/article/dn24026-ecosystems-still-feel-the-pain-of-ancient-extinctions.html | access-date = 2013-08-12 | archive-date = 2015-07-04 | archive-url = https://web.archive.org/web/20150704181952/https://www.newscientist.com/article/dn24026-ecosystems-still-feel-the-pain-of-ancient-extinctions.html | url-status = live }}</ref><ref name="DoughtyWolf2013">{{cite journal|last1=Doughty|first1=C. E.|last2=Wolf|first2=A.|last3=Malhi|first3=Y.|author-link3=Yadvinder Malhi|title=The legacy of the Pleistocene megafauna extinctions on nutrient availability in Amazonia|journal= [[Nature Geoscience]]|date= 2013-08-11|doi= 10.1038/ngeo1895|volume= 6|issue= 9|pages= 761–764|bibcode= 2013NatGe...6..761D}}</ref> Given that [[phosphorus]] availability is thought to limit productivity in much of the region, the decrease in its transport from the western part of the basin and from floodplains (both of which derive their supply from the uplift of the [[Andes]]) to other areas is thought to have significantly impacted the region's ecology, and the effects may not yet have reached their limits.<ref name="DoughtyWolf2013"/> In the sea, cetaceans and pinnipeds that feed at depth are thought to translocate nitrogen from deep to shallow water, enhancing [[Primary production#Oceanic production|ocean productivity]], and counteracting the activity of [[zooplankton]], which tend to do the opposite.<ref name="Roman2010">{{cite journal|last1= Roman|first1= J.|last2= McCarthy|first2= J.J.|title=The Whale Pump: Marine Mammals Enhance Primary Productivity in a Coastal Basin |journal=PLOS ONE|volume= 5|issue= 10|year= 2010|page= e13255|doi= 10.1371/journal.pone.0013255|pmc= 2952594|pmid= 20949007|bibcode= 2010PLoSO...513255R|doi-access= free}}</ref>

====Effect on methane emissions====
Large populations of megaherbivores have the potential to contribute greatly to the atmospheric concentration of [[methane]], which is an important [[greenhouse gas]]. Modern [[ruminant]] [[herbivores]] produce methane as a byproduct of [[foregut fermentation]] in digestion and release it through belching or flatulence. Today, around 20% of annual [[methane emissions]] come from livestock methane release. In the [[Mesozoic]], it has been estimated that [[sauropod]]s could have emitted 520 million tons of methane to the atmosphere annually,<ref name = "Wilkinson">{{cite journal
 | last = Wilkinson | first = D. M. |author2=Nisbet, E. G. |author3=Ruxton, G. D.
 | title = Could methane produced by sauropod dinosaurs have helped drive Mesozoic climate warmth?
 | journal = [[Current Biology]] | volume = 22 | issue = 9 | pages = R292–R293 | date = 2012-05-08
 | doi = 10.1016/j.cub.2012.03.042 | pmid = 22575462 | doi-access = free | bibcode = 2012CBio...22.R292W }}</ref> contributing to the warmer climate of the time (up to 10 °C (18 °F) warmer than at present).<ref name = "Wilkinson"/><ref name = "sauropod_methane">{{cite web | title = Dinosaur gases 'warmed the Earth' | work = BBC Nature News | date = 2012-05-07 | url = http://www.bbc.co.uk/nature/17953792 | access-date = 2012-05-08 | archive-date = 2015-12-01 | archive-url = https://web.archive.org/web/20151201084318/http://www.bbc.co.uk/nature/17953792 | url-status = live }}</ref> This large emission follows from the enormous estimated biomass of sauropods, and because methane production of individual herbivores is believed to be almost proportional to their mass.<ref name = "Wilkinson"/>

Recent studies have indicated that the extinction of megafaunal herbivores may have caused a reduction in [[atmospheric methane]]. This hypothesis is relatively new.<ref name = "Smith">{{Cite journal
  | last = Smith | first = F. A. |author2=Elliot, S. M. |author3=Lyons, S. K.
  | title = Methane emissions from extinct megafauna
  | journal = [[Nature Geoscience]] | volume = 3 | issue = 6| pages = 374–375
  | date = 2010-05-23
  | doi = 10.1038/ngeo877 |bibcode = 2010NatGe...3..374S}}</ref> One study examined the methane emissions from the [[American bison|bison]] that occupied the [[Great Plains]] of North America before contact with European settlers. The study estimated that the removal of the bison caused a decrease of as much as 2.2 million tons per year.<ref name = "Kelliher">{{Cite journal
  | last = Kelliher | first = F. M.  |author2=Clark, H.
  | title = Methane emissions from bison—An historic herd estimate for the North American Great Plains
  | journal = [[Agricultural and Forest Meteorology]] | volume = 150 | issue = 3 | pages = 473–577
  | date = 2010-03-15 | doi = 10.1016/j.agrformet.2009.11.019| bibcode =2010AgFM..150..473K}}</ref> Another study examined the change in the methane concentration in the atmosphere at the end of the [[Pleistocene epoch]] after the extinction of megafauna in the Americas. After early humans migrated to the Americas about 13,000 [[Before Present|BP]], their hunting and other associated ecological impacts led to the extinction of many megafaunal species there. Calculations suggest that this extinction decreased methane production by about 9.6 million tons per year. This suggests that the absence of megafaunal methane emissions may have contributed to the abrupt climatic cooling at the onset of the [[Younger Dryas]].<ref name = "Smith"/> The decrease in atmospheric methane that occurred at that time, as recorded in [[ice core]]s, was 2 to 4 times more rapid than any other decrease in the last half million years, suggesting that an unusual mechanism was at work.<ref name = "Smith"/>

==Gallery==

===Pleistocene extinct megafauna===
<gallery>
File:Dinornis novaezealandiae.png|[[Moa]] ''([[Dinornis]]'' pictured)
File:Diprotodon optatum (2).jpg|''[[Diprotodon optatum]]''
File:Varanus priscus Melbourne Museum.jpg|"[[Megalania]]" (''[[Varanus priscus]]'')
File:Panthera leo atrox Sergiodlarosa.jpg|[[American lion]]s (''Panthera atrox''')'''''
File:Woolly mammoth (Mammuthus primigenius) - Mauricio Antón.jpg|alt=Woolly mammoths vanished after humans invaded their habitat in Eurasia and N. America.|[[Woolly mammoth]]
File:Archaeoindris fontoynonti.jpg|The [[subfossil lemur]] ''[[Archaeoindris]]''
File:Giant Haasts eagle.jpg|[[Haast's eagle]]
File:Macrauchenia patachonica Life Reconstruction.png|Restoration of ''[[Macrauchenia]]'', a camel-sized member of the extinct ungulate order [[Litopterna]]
File:Doedicurus and Glyptodon.jpg|Life restoration of the [[glyptodont|glyptodonts]] ''[[Doedicurus]]'' (front) and ''[[Glyptodon]]''
</gallery>

=== Other extinct Cenozoic megafauna ===
<gallery>
File:Dromornis stirtoni.jpg|''[[Dromornis stirtoni]]'' 
File:Indricotherium11.jpg|alt=Asian indricothere rhino Paraceratherium was among the largest land mammals,  about twice a bush elephant's mass.|Asian [[Paraceratheriidae|paraceratheriid]] rhino ''[[Paraceratherium]]'' was among the largest land mammals<ref name="Tsubamoto2012">{{cite journal | doi = 10.4202/app.2011.0067 | title=Estimating body mass from the astragalus in mammals | journal=Acta Palaeontologica Polonica | date=2012 | pages= 259–265| first=T. | last=Tsubamoto| s2cid=54686160 }}</ref>  
File:Megalodon jaws on display at the National Baltimore Aquarium.jpg|Reconstructed jaws of [[megalodon]] (''Otodus megalodon'')
File:Deinotherium12.jpg|''[[Deinotherium]]'' 
File:Kelenken.jpg|''[[Kelenken guillermoi]]'' 
File:Gastornis.png|''[[Gastornis |Gastornis gigantea]]'' 
</gallery>

===Extant===
<gallery>
File:Nandu Rhea americana Tierpark Hellabrunn-1.jpg|[[Greater rhea]]
File:Kbnpsilverbackandchild 0.5.jpg|[[Eastern gorilla]]
File:Hunting Tiger Ranthambore.jpg|[[Bengal tiger]]
File:Polar Bear 2004-11-15.jpg|[[Polar bear]]
File:Ngorongoro Spitzmaulnashorn edit1crop.jpg|[[Black rhinoceros]]
File:Ovibos moschatus qtl3.jpg|[[Muskox]]
File:Alaska_moose.jpg|[[Moose]]
File:Nijlpaard.jpg|[[Hippopotamus]]
File:Mother and baby sperm whale.jpg|Adult [[sperm whale]] and calf
File:Killerwhales jumping.jpg|[[Orca]]s
File:Southern Cassowary 7071.jpg|[[Southern cassowary]]
File:Ostrich Struthio camelus Tanzania 3742 cropped Nevit.jpg|[[Common ostrich]]
File:SaltwaterCrocodile('Maximo').jpg|[[Saltwater crocodile]]
File:Komodo dragon Varanus komodoensis Ragunan Zoo 2.JPG|[[Komodo dragon]]
File:Anaconda Loreto Peru.jpg|[[Green anaconda]]
File:Velemlok čínský zoo praha 1.jpg|[[Chinese giant salamander]]
File:Mola alexandrini (Bump-head Mola).jpg|[[Giant sunfish]]
File:Lates niloticus 2.jpg|[[Nile perch]]
File:White shark.jpg|[[Great white shark]]
File:Manta alfredi fushivaru thila.jpg|[[Reef manta ray]]
File:Giant squid Ranheim2.jpg|Carcass of a [[giant squid]]
</gallery>

==See also==
{{div col|colwidth=30em}}
*[[Australian megafauna]]
*[[Bergmann's rule]]
*[[Charismatic megafauna]]
*[[Cope's rule]]
*[[Deep-sea gigantism]]
*[[Island gigantism]]
*[[Largest organisms]]
*[[Largest prehistoric animals]]
*[[List of heaviest land mammals]]
*[[List of largest mammals]]
*[[List of megafauna discovered in modern times]]
*[[Megafauna (mythology)]]
*[[Megafaunal wolf]]
*[[Megaflora]]
*[[Megaherb]]
*[[Quaternary extinction event]]
{{div col end}}

==Notes==
{{reflist| group = note}}

==References==
{{reflist
| colwidth = 30em
| refs =

}}

==External links==
* [https://web.archive.org/web/20141225044106/http://megafauna.com/table-of-contents/ Megafauna  – "First Victims of the Human-Caused Extinction"]

[[Category:Megafauna| ]]
[[Category:Extinction]]
[[Category:Zoology]]
[[Category:Animal size]]