Examine individual changes

'{{About|the Central and South American mammal|the cardinal sin|Sloth (deadly sin)|other uses|Sloth (disambiguation)}} {{pp-move-indef|small=yes}} {{Automatic taxobox | name = Sloths<ref name=msw3>{{MSW3 Gardner|pages=100–101|id=11800002}}</ref> | fossil_range = [[Early Oligocene]] to [[Holocene]] | image = Bradypus.jpg | image_caption = [[Brown-throated sloth]]<br/>(''Bradypus variegatus'')<br/>[[Gatun Lake]], [[Panama|Republic of Panama]] | taxon = Folivora | authority = Delsuc, Catzeflis, Stanhope, and Douzery, 2001 | subdivision_ranks = [[Family (biology)|Families]] | subdivision = [[Three-toed sloth|Bradypodidae]]<br /> [[Megalonychidae]]<br /> †[[Megatheriidae]]<br /> †[[Mylodontidae]]<br /> †[[Nothrotheriidae]] }} '''Sloths''' are [[mammal]]s classified in the [[family (biology)|families]] [[two-toed sloth|Megalonychidae]] (two-toed sloths) and [[three-toed sloth|Bradypodidae]] (three-toed sloths). There are six extant [[species]] of sloths. They are named after the [[Seven deadly sins|capital sin]] of [[Sloth (deadly sin)|sloth]] because they seem slow and lazy at first glance; however, their usual idleness is due to metabolic adaptations for conserving energy. Aside from their surprising bursts of speed during emergency flights from predators, other notable traits of sloths include their strong body, ability to swim and host [[Symbiosis|symbiotic]] [[algae]] on their fur. They are classified in the [[order (biology)|order]] [[Pilosa]] with [[anteater]]s, which sport a similar set of specialized claws. [[Extinction|Extinct]] sloth species include many [[megafauna]]l [[ground sloth]]s, some of which attained the size of elephants, as well as a few species of [[Thalassocnus|marine sloths]]. Extant sloths are medium-sized [[arboreal locomotion|arboreal]] (tree-dwelling) residents of the [[tropical rainforest|jungles]] of [[Central America|Central]] and [[South America]]. Sloths make very good habitats for other organisms, and a single sloth may be home to several species of moths, beetles, cockroaches, [[fungi]], [[ciliates]], and algae. ==Taxonomy and names== The sloth's taxonomic [[taxonomic rank|suborder]] is '''Folivora''', sometimes also called '''Phyllophaga''' (<small>[[Richard Owen|Owen]], 1842</small>) or '''Tardigrada''' (<small>[[John Latham (ornithologist)|Latham]] and Davies, 1795</small>). The first two names both mean "leaf-eaters"; derived from [[Latin]] and [[Greek language|Greek]], respectively. Names for the animals used by tribes in [[Ecuador]] include ''ritto'', ''rit'', and ''ridette'', mostly forms of the word "sleep", "eat", and "dirty" from [[Tagaeri]] tribe of [[Huaorani]].{{cn|date=March 2017}} The English word "[[wikt:sloth|sloth]]" (a derivative of the adjective "slow") is recorded as meaning [[Sloth (deadly sin)|"laziness", "indolence"]] from the twelfth century onwards, and is considered one of the [[seven cardinal sins]].<ref>Oxford English Dictionary, entry "sloth"</ref> It was first applied to the animal in the early seventeenth-century, as a [[calque]] (loan-word) of the Portuguese word ''preguiça'' ("laziness").<ref>http://www.etymonline.com/index.php?term=sloth</ref> The proper pronunciation is {{IPAc-en|'|s|l|oʊ|θ}} {{respell|SLOHTH|'}} or {{IPAc-en|'|s|l|ɒ|θ}} {{respell|SLOTH|'}}.<ref>The pronunciation {{IPAc-en|'|s|l|oʊ|θ}} is commonest in British English. The pronunciation {{IPAc-en|'|s|l|ɒ|θ}} is used in most Englishes.</ref> ==Ecology== [[File:MC Drei-Finger-Faultier.jpg|thumb|left|Feeding [[brown-throated three-toed sloth]] (''Bradypus variegatus''), [[Cahuita National Park]], [[Costa Rica]]]] Sloths are classified as [[folivore]]s, as the bulk of their diets consist of buds, tender shoots, and leaves, mainly of ''[[Cecropia]]'' trees. Some two-toed sloths have been documented as eating [[insect]]s, small reptiles, and birds as a small supplement to their diets. [[Linnaeus's two-toed sloth]] has recently been documented eating human faeces from open latrines.<ref>{{cite journal|author = Heymann, E. W.|author2 = Flores Amasifuén, C.|author3 = Shahuano Tello, N.|author4 = Tirado Herrera, E. T.|author5 = Stojan-Dolar, M|last-author-amp = yes|year = 2010|pages = 84–86|issue = 1|volume = 76|title = Disgusting appetite: Two-toed sloths feeding in human latrines|journal = Mammalian Biology|doi = 10.1016/j.mambio.2010.03.003}}</ref> They have made extraordinary adaptations to an [[arboreal]] browsing lifestyle. Leaves, their main food source, provide very little energy or nutrients, and do not digest easily. Sloths, therefore, have large, specialized, slow-acting [[stomach]]s with multiple compartments in which symbiotic [[bacteria]] break down the tough leaves. Sloths have the unique ability to protrude their tongues from their mouths {{convert|10|to|12|in|cm}}, an ability that is useful for collecting leaves just out of reach.<ref>{{cite web|url=http://www.srl.caltech.edu/personnel/krubal/rainforest/Edit560s6/www/animals/slothpage.html|title=Animals of the Rainforest-Sloth|work=caltech.edu}}</ref> As much as two-thirds of a well-fed sloth's body weight consists of the contents of its stomach, and the digestive process can take a month or more to complete. Since leaves provide little energy, sloths deal with this by a range of economy measures: they have very low [[metabolism|metabolic]] rates (less than half of that expected for a mammal of their size), and maintain low body temperatures when active (30–34&nbsp;°C or 86–93&nbsp;°F), and still lower temperatures when resting. Although unable to survive outside the tropical rainforests of South and Central America, within that environment sloths are outstandingly successful creatures. On [[Barro Colorado Island]] in [[Panama]], sloths have been estimated to comprise 70% of the [[biomass]] of arboreal mammals.<ref name = "Eisenberg2000b">{{Cite book | last = Eisenberg | first = John F. |author2=Redford, Kent H. | title = Mammals of the Neotropics, Volume 3: The Central Neotropics: Ecuador, Peru, Bolivia, Brazil | publisher = [[University of Chicago Press]] | date = May 15, 2000 | location = | pages = 624 (see p. 96) | isbn =978-0-226-19542-1 |oclc =493329394 | url = https://books.google.com/books?id=p2MDAzCeQQoC&pg=PA96 }}</ref> Four of the six living [[species]] are presently rated "least concern"; the [[maned three-toed sloth]] (''Bradypus torquatus''), which inhabits Brazil's dwindling [[Atlantic Forest]], is classified as "vulnerable",<ref name="iucn B torquatus">{{IUCN2014.1|assessor=Chiarello, A.|assessor2=Moraes-Barros, N.|last-assessor-amp=yes|year=2014|id=3036|title=Bradypus torquatus|downloaded=2015-09-13}}</ref> while the island-dwelling [[pygmy three-toed sloth]] (''B. pygmaeus'') is critically endangered. ==Physiology== Sloths have short, flat heads, big eyes, short snouts, stout bodies, long limbs, and tiny ears. Three-toed sloths also have stubby tails about 5-6 cm long. Sloths are about the size of small dogs, with the head and body having a combined length of 50 to 70&nbsp;cm. Almost all [[mammal]]s have seven [[cervical vertebrae]], including those with very short necks, such as [[elephant]]s and [[Cetacea|cetaceans]], and those with very long necks, such as [[giraffe]]s and [[Camelid|camels]]. The few exceptions include [[manatee]]s and two-toed sloths, which have only six cervical vertebrae, and three-toed sloths with nine cervical vertebrae.<ref>{{Cite journal|last=Narita|first=Yuichi|last2=Kuratani|first2=Shigeru|date=2005-03-15|title=Evolution of the vertebral formulae in mammals: A perspective on developmental constraints|url=http://onlinelibrary.wiley.com/doi/10.1002/jez.b.21029/abstract|journal=Journal of Experimental Zoology Part B: Molecular and Developmental Evolution|language=en|volume=304B|issue=2|pages=91–106|doi=10.1002/jez.b.21029|issn=1552-5015}}</ref> Sloth fur exhibits specialized functions: the outer hairs grow in a direction opposite from that of other mammals. In most mammals, hairs grow toward the [[Appendicular skeleton|extremities]], but because sloths spend so much time with their limbs above their bodies, their hairs grow away from the extremities to provide protection from the elements while they hang upside down. In most conditions, the fur hosts symbiotic algae, which provide [[camouflage]].<ref>{{Cite journal|last=Suutari|first=Milla|last2=Majaneva|first2=Markus|last3=Fewer|first3=David P.|last4=Voirin|first4=Bryson|last5=Aiello|first5=Annette|last6=Friedl|first6=Thomas|last7=Chiarello|first7=Adriano G.|last8=Blomster|first8=Jaanika|date=2010-01-01|title=Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with Trichophilus welckeri(Chlorophyta, Ulvophyceae)|url=http://dx.doi.org/10.1186/1471-2148-10-86|journal=BMC Evolutionary Biology|volume=10|pages=86|doi=10.1186/1471-2148-10-86|issn=1471-2148|pmc=2858742|pmid=20353556}}</ref> Because of the algae, sloth fur is a small ecosystem of its own, hosting many species of [[Commensalism|commensal]] and [[Parasitism|parasitic]] [[Arthropod|arthropods]].<ref>{{Cite journal|last=Gilmore|first=D. P.|last2=Da Costa|first2=C. P.|last3=Duarte|first3=D. P. F.|date=2001-01-01|title=Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses|url=http://www.scielo.br/scielo.php?script=sci_abstract&pid=S0100-879X2001000100002&lng=en&nrm=iso&tlng=en|journal=Brazilian Journal of Medical and Biological Research|volume=34|issue=1|pages=9–25|doi=10.1590/S0100-879X2001000100002|issn=0100-879X}}</ref> Some of the commensal arthropods are highly specific and are only found on a particular sloth species. Their long claws are their only defense against predators. A cornered sloth may swipe at its attackers in an effort to scare them away or wound them. Despite their apparent defenselessness, predators do not pose special problems: sloths blend in with the trees and, moving only slowly, do not attract attention. Only during their rare visits to the ground do they become vulnerable. The main predators of sloths are [[Jaguar|jaguars]], [[Ocelot|ocelots]], [[Harpy eagle|harpy eagles]], and humans.<ref>{{Cite journal|last=Moreno|first=Ricardo S.|last2=Kays|first2=Roland W.|last3=Samudio|first3=Rafael|date=2006-08-24|title=Competitive Release in Diets of Ocelot (Leopardus pardalis) and Puma (Puma concolor) after Jaguar (Panthera onca) Decline|url=https://academic.oup.com/jmammal/article/87/4/808/968843/Competitive-Release-in-Diets-of-Ocelot-Leopardus|journal=Journal of Mammalogy|volume=87|issue=4|pages=808–816|doi=10.1644/05-MAMM-A-360R2.1|issn=0022-2372}}</ref><ref>{{Cite journal|last=Aguiar-Silva|first=F. Helena|last2=Sanaiotti|first2=Tânia M.|last3=Luz|first3=Benjamim B.|date=2014-03-01|title=Food Habits of the Harpy Eagle, a Top Predator from the Amazonian Rainforest Canopy|url=http://www.bioone.org/doi/abs/10.3356/JRR-13-00017.1|journal=Journal of Raptor Research|volume=48|issue=1|pages=24–35|doi=10.3356/JRR-13-00017.1|issn=0892-1016}}</ref> The majority of recorded sloth deaths in [[Costa Rica]] are due to contact with [[electric power transmission|electrical lines]] and [[poaching|poachers]]. Their claws also provide another, unexpected deterrent to human hunters; when hanging upside-down in a tree, they are held in place by the claws themselves and often do not fall down even if shot from below. [[File:Two-toed sloth Costa Rica - cropped.jpg|thumb|right|[[Hoffman's two-toed sloth]] ''(Choloepus hoffmanni)'' feeding in [[Manuel Antonio National Park]] in [[Costa Rica]]]] Despite their adaptation to living in trees, sloths (like many other rainforest animals) make competent swimmers. This is likely to have been true of the extinct ground sloths, as well, as evidenced by the fact that megalonychid sloths were able to [[oceanic dispersal|colonise]] the [[Antilles]] by the [[Oligocene]], and that the megalonychid ''[[Pliometanastes]]'' and the [[Mylodontidae|mylodontid]] ''[[Thinobadistes]]'' were able to colonise North America about 9 million years ago, well before the existence of the [[Isthmus of Panama]]. Additionally, the [[Nothrotheriidae|nothrotheriid]] ''[[Thalassocnus]]'' of the west coast of South America became adapted to a semiaquatic [[Marine mammal|marine]] lifestyle.<ref name = "Muizen2004">{{cite journal | last = Muizon | first = C. de |author2=McDonald, H. G. |author3=Salas, R. |author4=Urbina, M. | title = The evolution of feeding adaptations of the aquatic sloth ''Thalassocnus'' | journal = Journal of Vertebrate Paleontology | volume = 24 | issue = 2 | pages = 398–410 |date=June 2004 | publisher = [[Society of Vertebrate Paleontology]] | doi = 10.1671/2429b | jstor = 4524727 }}</ref> Sloths move only when necessary and even then very slowly, because they only have about a quarter as much muscle tissue as other animals of similar weight. They usually move at an average speed of 4 m (10 ft) per minute, but can move at a marginally higher speed of 4.5 m (15 ft), if they are in immediate danger from a predator. Their specialised hands and feet have long, curved claws to allow them to hang upside down from branches without effort.<ref>{{Cite journal|last=Mendel|first=Frank C.|date=1985-01-01|title=Use of Hands and Feet of Three-Toed Sloths (Bradypus variegatus) during Climbing and Terrestrial Locomotion|url=http://www.jstor.org/stable/1381249|journal=Journal of Mammalogy|volume=66|issue=2|pages=359–366|doi=10.2307/1381249}}</ref> While they sometimes sit on top of branches, they usually eat, sleep, and even give birth hanging from branches. They sometimes remain hanging from branches even after death. On the ground, the maximum speed of sloths is 3&nbsp;m (10&nbsp;ft) per minute. Sloths are surprisingly strong swimmers and can reach speeds of 13.5 m (45 ft) per minute.<ref>{{Cite journal|last=Goffart|first=M.|date=1971|title=Function and Form in the sloth|url=|journal=International Series of Monographs in Pure and Applied Biology|volume=34|pages=94-95}}</ref> They use their long arms to paddle through the water and can easily cross rivers and swim between islands.<ref>{{Citation|last=BBC|title=Swimming sloth - Planet Earth II: Islands Preview - BBC One|date=2016-11-04|url=https://www.youtube.com/watch?v=ctutKTrf_NY|accessdate=2017-04-17}}</ref> Sloths have an amazing ability to reduce their already slow metabolism even further and slow their heart rate to less than a third of normal, allowing them to hold their breath underwater for up to 40 minutes.<ref>{{Cite journal|last=Britton|first=S. W.|date=1941-01-01|title=Form and Function in the Sloth|url=http://www.jstor.org/stable/2808832|journal=The Quarterly Review of Biology|volume=16|issue=1|pages=13–34}}</ref> <!--1.5 m (5 feet) per minute. They mostly move at 15–30&nbsp;cm (0.5–1.0&nbsp;ft) per minute.{{Citation needed|date=February 2008}} Which tree sloth are we citing here for speed?--> Sloths were thought to be among the most [[somnolence|somnolent]] animals, sleeping from 15 to 18 hours each day. In 2008, however, Dr. Neil Rattenborg and his colleagues from the Max Planck Institute for Ornithology in Starnberg, Germany, published a study testing sloth sleep patterns in the wild; this is the first study of its kind. The study indicated that sloths sleep just under 10 hours a day.<ref>{{cite news|last=Briggs |first=Helen |url=http://news.bbc.co.uk/2/hi/science/nature/7396356.stm |title=Article "Sloth's Lazy Image 'A Myth'" |publisher=BBC News |date=2008-05-13 |accessdate=2010-05-21}}</ref> Three-toed sloths are mostly [[Diurnality|diurnal]], while two-toed sloths are [[nocturnal]].<ref name = "Eisenberg2000">{{Cite book | last = Eisenberg | first = John F. |author2=Redford, Kent H. | title = Mammals of the Neotropics, Volume 3: The Central Neotropics: Ecuador, Peru, Bolivia, Brazil | publisher = [[University of Chicago Press]] | date = May 15, 2000 | location = | pages = 624 (see pp. 94–95, 97) | isbn =978-0-226-19542-1 |oclc =493329394 | url = https://books.google.com/books?id=p2MDAzCeQQoC&pg=PA94 }}</ref> [[File:SlothDWA.jpg|thumb|left|[[Three-toed sloth]] in the Dallas World Aquarium]] Sloths go to the ground to urinate and defecate about once a week, digging a hole and covering it afterwards. They go to the same spot each time and are vulnerable to predation while doing so. The reason for this risky behaviour is unknown, although some believe it is to avoid making noise while defecating from up high that would attract predators.<ref>{{Cite journal|title=Life of Mammals|author=David Attenborough|publisher=BBC}}</ref> Consistent with this, they reportedly relieve themselves from their branches during storms in the rainy season.<ref name = "Zoogoer">{{cite web|last = Stewart|first = Melissa|title = Slow and Steady Sloths|work = Smithsonian Zoogoer|publisher = [[Smithsonian Institution]]|date = November 2004|url = http://nationalzoo.si.edu/Publications/ZooGoer/2004/6/sloths.cfm|accessdate = 2009-09-14}}</ref> Another possible explanation is that the [[middens]] provide the sloths with one of their few methods of finding one another for breeding purposes, since their sense of smell is far more acute than their eyesight or hearing.<ref>{{Cite journal|title=David Attenborough's Life Stories|author=David Attenborough|publisher=BBC Radio 4; 8:50&nbsp;am 7 June 2009}}</ref> Still other recent studies have suggested that it might be relevant for maintaining the ecosystem in the sloths' fur.<ref>Title:A syndrome of mutualism reinforces the lifestyle of a sloth Authors:Jonathan N. Pauli, Jorge E. Mendoza, Shawn A. Steffan, Cayelan C.Carey, Paul J. Weimer and M. Zachariah Peery Journal:Proceedings of the Royal Society B</ref> Individual sloths tend to spend the bulk of their time feeding on a single "modal" tree; by burying their excreta near the trunk of that tree, they may help nourish it.<ref name = "Community">{{cite web|last = Montgomery|first = Sy|title = Community Ecology of the Sloth|work = Cecropia: Supplemental Information|publisher = [[Encyclopædia Britannica]]|url = http://www.britannica.com/EBchecked/topic/101053/cecropia/101053suppinfo/Supplemental-Information|accessdate = 2009-09-06}}</ref> Recently there has been some speculation that sloths go to the ground to defecate because of their mutually beneficial relationships with moths. While the sloth defecates, female moths that otherwise live on a sloth will get off and immediately lay their eggs directly on the fecal matter, on which the larvae survive until they mature to adulthood and are able to fly onto sloths. Incidentally, it appears that sloths benefit from their relationship with moths because the moths are responsible for fertilizing algae on the sloth, which provides them with nutrients.<ref>{{cite web|url=http://phenomena.nationalgeographic.com/2014/01/21/can-moths-explain-why-sloths-poo-on-the-ground/|title=Can Moths Explain Why Sloths Poo On the Ground?|author=Ed Yong|author-link=Ed Yong|work=Phenomena}}</ref> Infant sloths normally cling to their mothers' fur, but occasionally fall off. Sloths are very sturdily built and rarely die from a fall. In some cases, they die from a fall indirectly because the mothers prove unwilling to leave the safety of the trees to retrieve the young.<ref>{{Cite journal|last=Soares|first=C. A.|last2=Carneiro|first2=R. S.|date=2002-05-01|title=Social behavior between mothers × young of sloths Bradypus variegatus SCHINZ, 1825 (Xenarthra: Bradypodidae)|url=http://www.scielo.br/scielo.php?script=sci_abstract&pid=S1519-69842002000200008&lng=en&nrm=iso&tlng=en|journal=Brazilian Journal of Biology|volume=62|issue=2|pages=249–252|doi=10.1590/S1519-69842002000200008|issn=1519-6984}}</ref> Females normally bear one baby every year, but sometimes sloths' low level of movement actually keeps females from finding males for longer than one year.<ref>{{Cite journal|last=Pauli|first=Jonathan N.|last2=Peery|first2=M. Zachariah|date=2012-12-19|title=Unexpected Strong Polygyny in the Brown-Throated Three-Toed Sloth|url=http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0051389|journal=PLOS ONE|volume=7|issue=12|pages=e51389|doi=10.1371/journal.pone.0051389|issn=1932-6203|pmc=3526605|pmid=23284687}}</ref> Sloths are not particularly [[sexual dimorphism|sexually dimorphic]] and several zoos have received sloths of the wrong sex.<ref>{{cite news|title=Manly secret of non-mating sloth at London Zoo|url=http://www.bbc.co.uk/news/uk-england-london-11031719|website=BBC News|publisher=BBC|accessdate=30 April 2015|date=19 August 2010}}</ref><ref>{{cite news|title=Same-sex sloths dash Drusillas breeding plan|url=http://www.bbc.co.uk/news/uk-england-sussex-25233287|website=BBC News|publisher=BBC|accessdate=30 April 2015|date=5 December 2013}}</ref> ==Evolution== [[File:Nothrotheriops.jpg|thumb|right|Restoration of the [[Shasta ground sloth]] (''Nothrotheriops shastense'')]] Sloths belong to the superorder [[Xenarthra]], a group of [[Placentalia|placental]] [[mammal]]s that [[Evolution|evolved]] in South America around 60 million years ago,<ref>{{Cite journal|last=O'Leary|first=Maureen A.|last2=Bloch|first2=Jonathan I.|last3=Flynn|first3=John J.|last4=Gaudin|first4=Timothy J.|last5=Giallombardo|first5=Andres|last6=Giannini|first6=Norberto P.|last7=Goldberg|first7=Suzann L.|last8=Kraatz|first8=Brian P.|last9=Luo|first9=Zhe-Xi|date=2013-02-08|title=The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals|url=http://science.sciencemag.org/content/339/6120/662|journal=Science|language=en|volume=339|issue=6120|pages=662–667|doi=10.1126/science.1229237|issn=0036-8075|pmid=23393258}}</ref> although at least one study found that xenarthrans broke off from other placental mammals around 100 Mya.<ref>{{Cite journal|last=Svartman|first=Marta|last2=Stone|first2=Gary|last3=Stanyon|first3=Roscoe|date=2006-07-21|title=The Ancestral Eutherian Karyotype Is Present in Xenarthra|url=http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.0020109|journal=PLOS Genetics|volume=2|issue=7|pages=e109|doi=10.1371/journal.pgen.0020109|issn=1553-7404|pmc=1513266|pmid=16848642}}</ref> [[Anteaters]] and [[armadillos]] are also included among Xenarthra. The earliest xenarthrans were arboreal herbivores with sturdy spines, fused pelvises, stubby teeth, and small brains. The living sloths belong to two families, '''Megalonychidae''' ("two-toed" sloths) and '''Bradypodidae''' (three-toed sloths). All living sloths have in fact three [[toe]]s; the "two-toed" sloths, however, have only two [[finger]]s. Two-toed sloths generally move faster than three-toed sloths. Both types tend to occupy the same forests; in most areas, one species of three-toed sloth and one species of the larger two-toed sloth will jointly predominate. However, their adaptations contradict the actual relationship of the two families, which are more distant from each other than their outward similarity suggests. The common ancestor of the two families lived around 35 Mya, making the living forms exceptional examples of [[convergent evolution|convergent]] or [[parallel evolution]]. The modern two-toed sloths are far more closely related to the Megalonychidae ground sloths than to the living three-toed sloths. Whether the ground-dwelling Megalonychidae descended from tree-climbing ancestors or whether the two-toed sloths are really miniature ground sloths that have converted or reverted to arboreal life cannot be properly determined yet. The latter possibility seems slightly more likely, because the small ground sloths ''[[Acratocnus]]'' and ''[[Neocnus]]'', which were also able to climb, are among the closer relatives of the two-toed sloths, and these together were related to the huge ground sloths ''[[Megalonyx]]'' and ''[[Megalocnus]]''.<ref>{{Cite journal|last=Gaudin|first=Timothy J.|date=2004-02-01|title=Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence|url=https://academic.oup.com/zoolinnean/article/140/2/255/2624254/Phylogenetic-relationships-among-sloths-Mammalia|journal=Zoological Journal of the Linnean Society|volume=140|issue=2|pages=255–305|doi=10.1111/j.1096-3642.2003.00100.x|issn=0024-4082}}</ref> The evolutionary history of the three-toed sloths is not well known. No particularly close relatives have yet been identified. The ground sloths do not constitute a [[clade|monophyletic]] group. Rather, they make up a number of lineages, and as far as is known, until the [[Holocene]], most sloths were in fact ground-dwellers. The famous ''[[Megatherium]]'', for example, belonged to a lineage of ground sloths that was not very close to the living sloths and their ground-living relatives, like the small ''Neocnus'' or the massive ''Megalonyx''. Meanwhile, ''[[Mylodon]]'', among the last ground sloths to disappear, was only very distantly related to either of these.<ref name="Fariña2013">{{cite book|author1=Fariña, Richard A.|author2=Vizcaíno, Sergio F.|author3=De Iuliis, Gerry |title=Megafauna: Giant Beasts of Pleistocene South America|url=https://books.google.com/books?id=kUAKgNfiAvoC&pg=PA181|date=22 May 2013|publisher=Indiana University Press|isbn=0-253-00719-4|oclc= 779244424| page= 181}}</ref> ===Phylogeny=== The following sloth phylogeny was obtained by morphological analysis of craniodental characters, and places ''[[Three-toed sloth|Bradypus]]'' as the [[sister group]] to all other extant and extinct sloths (extant genera are in bold). {{clade | style = font-size: 90%;line-height:50% | label1 = &nbsp;&nbsp;&nbsp;&nbsp;[[Folivora]] |1={{clade |1={{clade |1={{clade | label1 = &nbsp;&nbsp;[[Bradypodidae]]&nbsp;&nbsp; |1='''''[[Bradypus]]''''' }} |2={{clade | label1 = &nbsp;&nbsp;[[Megatherioidea]]&nbsp;&nbsp; |1={{clade |1={{clade | label1 = &nbsp;&nbsp;[[Megalonychidae]]&nbsp;&nbsp; | label2 = [[Megatheria]] |1={{clade |1=''[[Megalonyx]]'' |2={{clade |1={{clade |1=''[[Acratocnus]]'' |2='''''[[Choloepus]]''''' |3=''[[Megalocnus]]'' |4=''[[Neocnus]]'' }} |2=''[[Pliometanastes]]'' }} }} |2={{clade | label1 = &nbsp;&nbsp;[[Megatheriidae]]&nbsp;&nbsp; |1={{clade |1={{clade |1=''[[Eremotherium]]'' |2=''[[Megatherium]]'' }} |2=''[[Planops]]'' }} | label2 = &nbsp;&nbsp;[[Nothrotheriidae]]&nbsp;&nbsp; |2={{clade |1={{clade |1=''[[Nothrotheriops]]'' |2=''[[Nothrotherium]]'' }} |2=''[[Nothropus]]'' }} }} |3=''[[Hapalops]]'' }} |2=''[[Pelecyodon]]'' }} | label2 = &nbsp;&nbsp;[[Mylodontidae]]&nbsp;&nbsp; |2={{clade |1={{clade |1={{clade |1={{clade |1=''[[Lestodon]]'' |2=''[[Thinobadistes]]'' }} |2=''[[Glossotherium]]'' }} |2=''[[Mylodon]]'' |3=''[[Paramylodon]]'' }} |2=''[[Scelidotherium]]'' }} }} }} }} }} However, a limited 2016 study of [[retrovirus]] and [[mitochondrial DNA]] sequences groups ''[[Two-toed sloth|Choloepus]]'' with ''Mylodon'', and ''Bradypus'' with ''[[Nothrotheriops]]''.<ref name="Slater2016">{{cite journal|last1=Slater|first1=G. J.|last2=Cui|first2= P.|last3= Forasiepi|first3=A. M.|last4= Lenz|first4=D.|last5= Tsangaras|first5=K.|last6= Voirin|first6=B.|last7=de Moraes-Barros|first7=N.|last8= MacPhee|first8=R. D. E.|last9=Greenwood|first9=A. D.|title=Evolutionary Relationships among Extinct and Extant Sloths: The Evidence of Mitogenomes and Retroviruses|journal=Genome Biology and Evolution|volume= 8|issue=3|date= 2016-02-14|pages= 607–621|doi= 10.1093/gbe/evw023}}</ref> {{clade | style = font-size: 90%;line-height:50% | label1 = &nbsp;&nbsp;&nbsp;&nbsp;[[Folivora]] |1={{clade |1={{clade |1={{clade | label1 = &nbsp;&nbsp;[[Bradypodidae]]&nbsp;&nbsp; |1='''''[[Bradypus]]''''' }} |2={{clade | label1 = &nbsp;&nbsp;[[Nothrotheriidae]]&nbsp;&nbsp; |1=''[[Nothrotheriops]]'' }} }} |2={{clade |1={{clade | label1 = &nbsp;&nbsp;[[Megalonychidae]]&nbsp;&nbsp; |1='''''[[Choloepus]]''''' }} |2={{clade | label1 = &nbsp;&nbsp;[[Mylodontidae]]&nbsp;&nbsp; |1=''[[Mylodon]]'' }} }} }} }} ==Classification== '''Suborder Folivora (sloths)''' * '''Family [[Bradypodidae]] (three-toed sloths)''' ** ''[[Bradypus]]'' *** [[Pygmy three-toed sloth]] (''Bradypus pygmaeus'') *** [[Maned sloth]] (''Bradypus torquatus'') *** [[Pale-throated sloth]] (''Bradypus tridactylus'')) *** [[Brown-throated sloth]] (''Bradypus variegatus'') * '''Family [[Megalonychidae]] (two-toed sloths and extinct ground sloths)''' **Subfamily [[Choloepodinae]] *** ''[[Acratocnus]]'' *** ''[[Choloepus]]'' ([[two-toed sloth]]s) **** [[Linnaeus's two-toed sloth]] (''Choloepus didactylus'') **** [[Hoffmann's two-toed sloth]] (''Choloepus hoffmanni'') *** ''[[Neocnus]]'' **Subfamily [[Megalonychinae]] *** ''[[Megalocnus]]'' *** ''[[Megalonyx]]'' *** ''[[Pliometanastes]]'' **Incertae sedis: ''[[Imagocnus]]'' * '''Family [[Megatheriidae]] (extinct ground sloths)''' ** ''[[Eremotherium]]'' ** ''[[Hapalops]]'' ** ''[[Megatherium]]'' ** ''[[Pelecyodon]]'' ** ''[[Prepotherium]]'' ** ''[[Promegatherium]]'' * '''Family [[Mylodontidae]] (extinct ground sloths)''' ** ''[[Chubutherium]]'' ** ''[[Glossotherium]]'' ** ''[[Lestodon]]'' ** ''[[Mylodon]]'' ** ''[[Paramylodon]]'' ** ''[[Scelidotherium]]'' **''[[Thinobadistes]]'' * '''Family [[Nothrotheriidae]] (extinct ground and marine sloths)''' ** ''[[Mionothropus]]'' ** ''[[Nothropus]]'' ** ''[[Nothrotheriops]]'' ** ''[[Nothrotherium]]'' ** ''[[Pronothrotherium]]'' ** ''[[Thalassocnus]]''[[File:Scelidotherium leptocephalum side.jpg|thumb|''<nowiki/>[[Scelidotherium|Scelidotherium leptocephalum]]'' [[fossil]], [[Muséum national d'histoire naturelle]], Paris]] [[File:Thalassocnus.jpg|thumb|''Thalassocnus'' skeleton in its hypothetical swimming pose, [[Muséum national d'histoire naturelle]], Paris]] ==Extinctions== [[File:Megatherium americanum Skeleton NHM.JPG|thumb|right|''[[Megatherium]]'' fossil, [[Natural History Museum, London|Natural History Museum]], [[London]]]] Until about 10,000 years ago, ground sloths such as ''[[Megatherium]]'' lived in [[South America]] as well as in much of [[North America]]; they colonized the latter as part of the [[Great American Interchange]]. Along with many other animals, however, they disappeared shortly after the appearance of humans on both continents. Large amounts of evidence suggest human hunting contributed to the extinction of the American [[megafauna]], like that of [[North Asia]], [[Australia]], [[New Zealand]], and [[Madagascar]].<ref name="autogenerated2">{{cite web|url=http://www.bbc.co.uk/nature/wildfacts/factfiles/456.shtml Wildfacts|title=Megatherium|archive-url=http://web.archive.org/web/20140201215430/http://www.bbc.co.uk/nature/wildfacts/factfiles/456.shtml|archive-date=2014-02-01|work=[[BBC]] Science & Nature|accessdate=2017-01-23}}</ref> Simultaneous climate change that came with the end of the last [[ice age]] may have also played a role in some cases. However, the survival of ''[[Megalocnus]]'' on the [[Antilles]] until about 5000 years ago (after these islands were finally settled by humans), long after other ground sloths died out on the mainland, points toward human activities as the cause of extinction.<ref name="Steadman">{{cite journal | last = Steadman | first = D. W. |author2=Martin, P. S. |author3=MacPhee, R. D. E. |author4=Jull, A. J. T. |author5=McDonald, H. G. |author6=Woods, C. A. |author7=Iturralde-Vinent, M. |author8=Hodgins, G. W. L. | author1link = David Steadman | author2link = Paul S. Martin | 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 | publisher = [[United States National Academy of Sciences|National Academy of Sciences]] | date = 2005-08-16 | url = http://www.pnas.org/content/102/33/11763.abstract | doi = 10.1073/pnas.0502777102 | accessdate = 2009-01-24 | pmid = 16085711 | pmc = 1187974}}</ref> In [[Peru]] and [[Chile]], sloths of the genus ''[[Thalassocnus]]'' adapted to a coastal marine lifestyle beginning in the late [[Miocene]]. Initially they just stood in the water, but over a span of 4 million years they eventually evolved into swimming creatures.<ref name = "Amsonetal2014">{{cite journal | last1 = Amson | first1 = E. | last2 = Muizon | first2 = C. de | last3 = Laurin | first3 = M. | last4 = Argot | first4 = C. |last5 = Buffrénil | first5 = V. de | title = Gradual adaptation of bone structure to aquatic lifestyle in extinct sloths from Peru | journal = Proceedings of the Royal Society B: Biological Sciences | volume = 281 | issue = 1782 | pages = 1–6|date=2014 | publisher = [[Royal Society of London]] | url=http://rspb.royalsocietypublishing.org/content/281/1782/20140192.abstract | doi=10.1098/rspb.2014.0192 | pmid=24621950 | pmc=3973278}}</ref> It is thought that when the [[Isthmus of Panama]] closed about 3 million years ago the water grew colder, perhaps contributing to their extinction by the late [[Pliocene]]. The plants these sloths fed on may have grown sparse, or they may have been unable to adapt to the lower water temperatures. ==Conservation== In Costa Rica, the Aviarios Sloth Sanctuary cares for wounded and abandoned sloths. About 130 animals have been released back into the wild.<ref>{{Cite news | author = Sevcenko, Melanie | title = Sloth sanctuary nurtures animals back to health | work = Deutsche Welle | accessdate = 2013-04-18 | date = 2013-04-17 | url = http://www.dw.de/sloth-sanctuary-nurtures-animals-back-to-health/a-16750190 }}</ref> However, a report in May 2016 featured two former veterinarians at the facility who were intensely critical of the sanctuary's efforts, accusing the sanctuary of mistreating the animals.<ref>{{cite news | author = Schelling, Ameena | title = Famous Sloth Sanctuary Is A Nightmare For Animals, Ex-Workers Say | work = The Dodo | accessdate = 2016-05-20 | date = 2016-05-19 | url = https://www.thedodo.com/sloths-sanctuary-nightmare-1807794384.html}}</ref> [[The Sloth Institute Costa Rica]] is also known for caring, rehabilitating and releasing sloths back into the wild. <ref>{{Cite web|url=www.theslothinstitutecostarica.org|title=The Sloth Institute website|last=|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}}</ref> ==In popular culture== Sloths gained popularity during the last decade, with the release of the first of the ''[[Ice Age (franchise)|Ice Age]]'' movies, which featured Sid, a prehistoric ground sloth, as a central character.<ref name="pop-time">{{cite news|url=http://entertainment.time.com/2013/03/22/how-sloths-took-over-pop-culture-the-world/|title=How Sloths Took Over Pop Culture, The World|date=22 March 2013|publisher=Time Magazine|last1=Rothman|first1=Lily|website=Time.com|accessdate=19 June 2015}}</ref> ''[[The Croods]]'' features a sloth as a family pet.<ref name="pop-variety">{{cite news|last1=Marechal|first1=Aj|title=Animal Planet Dives Into Pop Culture’s Sloth Fixation|url=http://variety.com/2013/tv/news/animal-planet-dives-into-pop-cultures-sloth-fixation-1200774935/|publisher=Variety|accessdate=19 June 2015|date=29 October 2013}}</ref> In Disney's animated film ''[[Zootopia]]'', a sloth named Flash works alongside many other sloths at the [[Department of Motor Vehicles]]. They all speak and perform actions extremely slowly, much to the frustration of the other characters.<ref>http://variety.com/2015/film/news/zootopia-trailer-dmv-sloths-1201646717/</ref> == See also == * [[Arthropods associated with sloths]] * [[Ground sloth]] * [[Pilosans of the Caribbean]] * [[Sloth moth]] ==References== {{reflist|30em}} ==External links== {{wiktionary}} {{commons category|Folivora}} {{Americana Poster}} * [http://animals.nationalgeographic.com/animals/mammals/two-toed-sloth.html?nav=A-Z Two-toed sloth page] at [[National Geographic Society|National Geographic]] website * [http://animals.nationalgeographic.com/animals/mammals/three-toed-sloth.html Three-toed sloth page] at [[National Geographic Society|National Geographic]] website * [http://www.srl.caltech.edu/personnel/krubal/rainforest/Edit560s6/www/animals/slothpage.html Caltech sloth page] * [http://www.ogphoto.com/slothrescuecenter/main.htm Aviarios del Caribe] Sloth Sanctuary (open to tourists, and close to the cruise ship pier, in Costa Rica). * [https://web.archive.org/web/20130502202941/http://www.sloth-world.org/ Sloth World: An online bibliography and database of sloth papers from around the world (archived from 2013-05-02)] * [http://www.sloths.org Pictures from sloths.org] * [http://www.bbc.com/news/magazine-26734289 The woman who lost a dog and gained 200 sloths] (2014-04-03 BBC news story) {{Pilosa}} {{Use dmy dates|date=November 2011}} [[Category:Sloths| ]] [[Category:Clawed herbivores]] [[Category:Folivores]] [[Category:Pilosans]] [[Category:Extant Rupelian first appearances]]'