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'{{short description|Genus of mammals}} {{Automatic Taxobox | name = Three-toed sloths<ref name=msw3>{{MSW3 Pilosa | id = 11800004 | pages=100–101}}</ref> | image = Bradypus.jpg | image_caption = [[Brown-throated three-toed sloth]] (''Bradypus variegatus'') | taxon = Bradypus | authority = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]] | display_parents = 2 | type_species = ''[[Pale-throated sloth|Bradypus tridactylus]]'' | type_species_authority = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]] | subdivision_ranks = [[Species]] | subdivision = 4, see [[#Species|text]] | range_map = Bradypus_Range.png | range_map_caption = Green: ''B. variegatus'', blue: ''B. tridactylus'', red: ''B. torquatus'' }} The '''three-toed sloths''' are [[arboreal locomotion|arboreal]] [[neotropical]] mammals (also known as "three-fingered" sloths).<ref name="Delsuc2019" /> They are the only members of the [[genus]] '''''Bradypus''''' and the [[family (biology)|family]] '''Bradypodidae'''. The four living species of three-toed sloths are the [[brown-throated sloth]], the [[maned sloth]], the [[pale-throated sloth]], and the [[pygmy three-toed sloth]]. In complete contrast to past morphological studies, which tended to place ''Bradypus'' as the [[sister group]] to all other [[folivora]]ns, molecular studies place them nested within the sloth superfamily [[Megatherioidea]], making them the only surviving members of that radiation.<ref name="Presslee2019" /><ref name="Delsuc2019" /> ==Extant species== {| class="wikitable" |- ! Image !! Scientific name !! Common name !! Distribution |- | [[File:Bradypus pygmaeus.jpg|120px]] || ''B. pygmaeus'' || [[Pygmy three-toed sloth]]|| Isla Escudos de Veraguas (Panama) |- | [[File:PisaMammalGallery (6).JPG|120px]] || ''B. torquatus''|| [[Maned three-toed sloth]] || Atlantic coastal rainforest of southeastern Brazil |- |[[File:Bradypus tridactylus -Parque del Este, Caracas, Venezuela-8 (2).jpg|120px]] || ''B. tridactylus'' || [[Pale-throated three-toed sloth]] ||Part of northern South America, including Guyana, Suriname, French Guiana, eastern Venezuela and Brazil north of the Amazon River |- |[[File:Bicho-preguiça 3.jpg|120px]] || ''B. variegatus''|| [[Brown-throated three-toed sloth]] || Central America and much of north and central South America, from Honduras through Colombia, Venezuela, Ecuador, eastern Peru, Bolivia and Brazil |- |} ==Evolution== A study of mitochondrial [[cytochrome b]] and [[MT-RNR2|16S rRNA]] sequences suggests that ''[[Maned sloth|B. torquatus]]'' diverged from ''[[Brown-throated sloth|B. variegatus]]'' and ''[[Pale-throated sloth|B. tridactylus]]'' about 12 million years ago, while the latter two split 5 to 6 million years ago. The diversification of ''B. variegatus'' lineages was estimated to have started 4 to 5 million years ago.<ref name="de Moraes-Barros2011">{{cite journal|last1=de Moraes-Barros|first1=N.|last2= Silva|first2=J. A. B.|last3= Morgante|first3=J. S.|title= Morphology, molecular phylogeny, and taxonomic inconsistencies in the study of ''Bradypus'' sloths (Pilosa: Bradypodidae)|journal=Journal of Mammalogy|volume= 92|issue =1|date= 2011-02-16|pages= 86–100|doi= 10.1644/10-MAMM-A-086.1}}</ref> ===Relation to the two-toed sloth=== Both types of [[sloth]] tend to occupy the same forests; in most areas, a particular species of three-toed sloth and a single species of the somewhat larger and generally faster-moving [[two-toed sloth]] will jointly predominate. Although similar in overall appearance, the two [[genus|genera]] are placed in different families. Recent [[phylogenetic]] analyses support the morphological data from the 1970s and 1980s that the two genera are not closely related and that each adopted their [[arboreal]] lifestyles independently.<ref name=Hoss>{{cite journal | last = Hoss | first = Matthias | author2 = Dilling, Amrei| author3 = Currant, Andrew| author4 = Paabo, Svante | title = Molecular phylogeny of the extinct ground sloth ''Mylodon darwinii'' | journal = [[Proceedings of the National Academy of Sciences]] | volume = 93 | issue = 1 | pages = 181–185 | date = 9 Jan 1996 | pmid = 8552600 | doi=10.1073/pnas.93.1.181 | pmc=40202| bibcode = 1996PNAS...93..181H }}</ref> From morphological studies it was unclear from which [[ground-dwelling sloth]] taxa the three-toed sloths evolved or whether they retained their arboreality from the last common ancestor of extant sloths. The two-toed sloths were thought on the basis of morphology to nest phylogenetically within one of the divisions of ground-dwelling [[Caribbean sloth]]s.<ref name = "White">{{Cite book | last = White | first = J. L. | author-link = | last2 = MacPhee | first2 = R. D. E. | author2-link = | title = Biogeography of the West Indies: Patterns and Perspectives | editor-last = Woods | editor-first = C. A. | editor2-last = Sergile | editor2-first = F. E. | publisher = [[CRC Press]] | year = 2001 | chapter =The sloths of the West Indies: a systematic and phylogenetic review | chapterurl =https://books.google.com/books?id=kDchYICxSDsC&pg=PA201&lpg=PA201&dq=The+sloths+of+the+West+Indies:+A+systematic+and+phylogenetic+review&source=bl&ots=nE1h0uppfJ&sig=4-pNcNeA5p17LC33-Zq38BeB0iY&hl=en&ei=OgwbS625CYLOsQOy27yRBw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAoQ6AEwAA#v=onepage&q=The_sloths_of_the_West_Indies%3A_A_systematic_and_phylogenetic_review | pages = 201–235 | url = https://books.google.com/books?id=kDchYICxSDsC&printsec=frontcover#v=onepage&q&f=false | isbn = 978-0-8493-2001-9}}</ref> Our understanding of sloth phylogeny has recently been greatly revised by molecular studies, based on [[collagen]]<ref name="Presslee2019" /> and [[mitochondrial DNA]]<ref name="Delsuc2019" /> sequences. These investigations consistently place three-toed sloths within Megatherioidea, close to ''[[Megalonyx]]'', [[megatheriid]]s and [[nothrotheriid]]s, and two-toed sloths close to [[mylodontid]]s, while moving the Caribbean sloths to a separate, [[basal (phylogenetics)|basal]] branch of the sloth evolutionary tree.<ref name="Presslee2019">{{cite journal|last1= Presslee|first1= S.|last2= Slater|first2=G. J.|last3= Pujos|first3= F.|last4= Forasiepi|first4=A. M.|last5= Fischer|first5= R.|last6= Molloy|first6= K.|last7= Mackie|first7= M.|last8= Olsen|first8=J. V.|last9= Kramarz|first9= A.|last10= Taglioretti|first10= M.|last11= Scaglia|first11= F.|last12= Lezcano|first12= M.|last13= Lanata|first13=J. L.|last14= Southon|first14= J.|last15= Feranec|first15= R.|last16= Bloch|first16= J.|last17= Hajduk|first17= A.|last18= Martin|first18=F. M.|last19= Gismondi|first19= R. S.|last20= Reguero|first20 =M.|last21=de Muizon|first21= C.|last22= Greenwood|first22= A.|last23= Chait|first23=B. T.|last24= Penkman|first24= K.|author24-link=Kirsty Penkman|last25= Collins|first25= M.|last26= MacPhee|first26= R.D.E.|title= Palaeoproteomics resolves sloth relationships|journal=Nature Ecology & Evolution|volume= 3|issue= 7|pages= 1121–1130|year= 2019|doi= 10.1038/s41559-019-0909-z|pmid= 31171860|url= https://www.semanticscholar.org/paper/5fb11e51d27f6af29edf9815cc39b1c89b9f9567}}</ref><ref name="Delsuc2019">{{cite journal|last1= Delsuc|first1= F.|last2= Kuch|first2= M.|last3= Gibb|first3=G. C.|last4= Karpinski|first4= E.|last5= Hackenberger|first5= D.|last6= Szpak|first6= P.|last7= Martínez|first7=J. G.|last8= Mead|first8=J. I.|last9= McDonald|first9=H. G.|last10= MacPhee|first10= R.D.E.|last11= Billet|first11= G.|last12= Hautier|first12= L.|last13= Poinar|first13=H. N.|title= Ancient Mitogenomes Reveal the Evolutionary History and Biogeography of Sloths|journal= Current Biology|volume= 29|issue= 12|pages= 2031–2042.e6|year= 2019|doi= 10.1016/j.cub.2019.05.043|pmid= 31178321|url= https://www.semanticscholar.org/paper/f9d958012e81c419298dd3e8b823ecfb4f90fd2e}}</ref> These results provide further strong support for the long-held belief that arboreality arose separately in the two genera via [[convergent evolution|convergent]] paths. ==Characteristics== Famously slow-moving, a sloth travels at an average speed of {{Convert|0.24|km/h|2|abbr=on}}.<ref name=infoplease>{{cite web|url=http://www.infoplease.com/ipa/A0004737.html|title=Speed of Animals|work=infoplease.com}}</ref> Three-toed sloths are about the size of a small dog or a large cat, with the head and body having a combined length around {{Convert|45|cm|0|abbr=on}} and a weight of {{Convert|3.5|-|4.5|kg|0|abbr=on}}. Unlike the two-toed sloths, they also have short tails of {{Convert|6|-|7|cm|0|abbr=on}}, and they have three clawed toes on each limb. All sloths have three digits on their [[hindlimb]]s; the difference is found in the number of digits on the [[forelimb]]s; thus they are sometimes referred to as three-fingered sloths.<ref>Judy Avey-Arroyo for Gage, L. J. (2008). ''Hand-Rearing Wild and Domestic Mammals'', Iowa State University Press, 2002, pages 81-89.{{doi|10.1002/9780470385005.ch12}}</ref> However, sloths are generally regarded as [[quadruped]]s. ==Behavior== Unlike the [[two-toed sloth]], three-toed sloths are exceptionaly good at fucking people. They are still slow in trees.<ref name="National Geographic">[http://animals.nationalgeographic.com/animals/mammals/three-toed-sloth/ Three-toed Sloth], National Geographic.</ref> The muscles that sloths use to grip and produce a pulling motion are much more prominent than those that produce a pushing motion.<ref>{{Cite journal|last=Olson|first=Rachel A.|last2=Glenn|first2=Zachary D.|last3=Cliffe|first3=Rebecca N.|last4=Butcher|first4=Michael T.|date=2018-12-01|title=Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)|url=https://doi.org/10.1007/s10914-017-9411-z|journal=Journal of Mammalian Evolution|language=en|volume=25|issue=4|pages=573–588|doi=10.1007/s10914-017-9411-z|issn=1573-7055}}</ref> This means that they struggle to support their body weight when walking on all four limbs, so travelling on the ground is a dangerous and laborious process.<ref>{{Citation|last=Keating|first=Ian D.|title=Audacious Sloth|date=2018-01-01|url=https://www.flickr.com/photos/ian-arlett/26121756518/|access-date=2020-03-30}}</ref> Three-toed sloths are arboreal (tree-dwelling), with a body adapted to hang by their limbs. Large, curved claws and muscles specifically adapted for strength and stamina help sloths to keep a strong grip on tree branches.<ref name="Olson2018">{{Cite journal|last= Olson|first= R.A.|last2= Glenn|first2= Z.D.|last3= Cliffe|first3= R.N.|last4= Butcher|first4= M.T.|date= 2018-12-01|title= Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)|journal= Journal of Mammalian Evolution|volume= 25|issue= 4|pages= 573–588|doi=10.1007/s10914-017-9411-z}}</ref> The abdominal organs close to their diaphragm (such as their stomach, liver and kidneys) are attached to their lower ribs (or pelvic girdle in the latter case) by fibrinous adhesions, which prevent the weight of these organs from compressing their lungs when hanging, making inhalation easier.<ref name="Cliffe2014">{{Cite journal|last= Cliffe|first= R.N.|last2= Avey-Arroyo|first2= J.A.|last3= Arroyo|first3= F.J.|last4= Holton|first4= M.D.|last5= Wilson|first5= R.P.|date= 2014-04-30|title= Mitigating the squash effect: sloths breathe easily upside down|doi= 10.1098/rsbl.2014.0172|journal= Biology Letters|volume= 10|issue= 4|page= 20140172|pmc= 4013704|pmid= 24759371}}</ref> They live high in the canopy, but descend once a week to defecate on the forest floor. During this week-long interval their feces and urine accumulate to about a third of their total body mass.<ref name="Cliffe2014" /> It takes about a month for a single leaf to pass through their four-chambered stomach and digestive tract.<ref>{{Cite journal|last=Cliffe|first=Rebecca N.|last2=Haupt|first2=Ryan J.|last3=Avey-Arroyo|first3=Judy A.|last4=Wilson|first4=Rory P.|date=2015-04-02|title=Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus)|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389270/|journal=PeerJ|volume=3|doi=10.7717/peerj.875|issn=2167-8359|pmc=4389270|pmid=25861559}}</ref> Although they get most of their fluids from the  leaves that they eat, they have been observed drinking directly from rivers.<ref>{{Cite journal|last=Cliffe|first=Rebecca N.|last2=Haupt|first2=Ryan J.|date=2018|title=Hanging out for a drink|url=https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/fee.1955|journal=Frontiers in Ecology and the Environment|language=en|volume=16|issue=8|pages=446–446|doi=10.1002/fee.1955|issn=1540-9309}}</ref> Because of their slow metabolism, they do not need to ingest many leaves on a daily basis; however, when ambient temperatures are high, the symbiotic microbes and bacteria present in their gut will break down and ferment food at a faster rate.<ref name="Cliffe2015">{{Cite journal|last= Cliffe|first= R.N.|last2= Haupt|first2= R.J.|last3= Avey-Arroyo|first3= J.A.|last4= Wilson|first4= R.P.|date= 2015-04-02|title= Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (''Bradypus variegatus'')|journal= PeerJ|volume= 3|doi= 10.7717/peerj.875|pmc= 4389270|pmid= 25861559}}</ref> Conversely, when temperatures are lower, sloths will consume less, which is opposite to what has been observed in most other mammals.<ref>{{Cite journal|last=Cliffe|first=Rebecca N.|last2=Haupt|first2=Ryan J.|last3=Avey-Arroyo|first3=Judy A.|last4=Wilson|first4=Rory P.|date=2015-04-02|title=Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus)|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389270/|journal=PeerJ|volume=3|doi=10.7717/peerj.875|issn=2167-8359|pmc=4389270|pmid=25861559}}</ref> Their long, coarse fur often appears greenish, not due to pigment, but to algae growing on it. Sloths' greenish color and their sluggish habits provide an effective camouflage; hanging quietly, sloths resemble a bundle of leaves. They move between different trees up to four times a day, although they prefer to keep to a particular type of tree, which varies between individuals, perhaps as a means of allowing multiple sloths to occupy overlapping home ranges without competing with each other.<ref name=EoM>{{cite book|editor= Macdonald, D.|author= Dickman, Christopher R.|year= 1984|title= The Encyclopedia of Mammals|publisher= Facts on File|location= New York|pages= [https://archive.org/details/encyclopediaofma00mals_0/page/776 776–779]|isbn= 0-87196-871-1|url-access= registration|url= https://archive.org/details/encyclopediaofma00mals_0/page/776}}</ref> Three-toed sloths are predominantly [[Diurnality|diurnal]], although they can be active at any hour of the day, while two-toed sloths are [[nocturnal]].<ref name = "Eisenberg2000">{{Cite book | last = Eisenberg | first = John F. | authorlink = | 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> ===Lifecycle=== [[File:Three-toed sloth crossing road in Costa Rica.jpg|thumb|Three-toed sloth crossing a road in Alajuela, Costa Rica]] Members of this genus tend to live around 25 to 30 years, reaching sexual maturation at three to five years of age. Three-toed sloths do not have a mating season and breed year round. Females give birth to a single young after a [[gestation]] period around six months. The offspring cling to their mother's bellies for around nine months. They are [[weaning|weaned]] around nine months of age, when the mother leaves her home territory to her offspring and moves elsewhere. Adults are solitary, and mark their territories using anal [[scent gland]]s and [[dung midden]]s.<ref name=EoM/> Male three-toed sloths are attracted to females in [[estrus]] by their screams echoing throughout the canopy. Sloth copulation lasts an average of 25 minutes.<ref>{{cite journal | author = Gilmore, D.P.| year = 2000 | title = An update on the physiology of two- and three-toed sloths | journal = Brazilian Journal of Medical and Biological Research | volume = 33 | issue = 2 | pages = 129–146 | doi = 10.1590/S0100-879X2000000200001| pmid = 10657054 |display-authors=etal}}</ref> Male three-toed sloths are strongly polygamous, and exclude competitors from their territory. Males are also able to compete with one another within small habitable territories.<ref>{{cite journal |author1=Pauli, J.N. |author2=Peery, M.Z. |lastauthoramp=yes | year = 2012 | title = Unexpected strong polygyny in the brown-throated three-toed sloth | journal = PLOS ONE | volume = 7 | issue = 12 | pages = e51389 | doi = 10.1371/journal.pone.0051389 | pmid=23284687 | pmc=3526605|bibcode=2012PLoSO...751389P }}</ref> The home ranges used by wild [[brown-throated three-toed sloth]]s in [[Costa Rica]] include [[Theobroma cacao|cacao]], pasture, [[riparian forests]], peri-urban areas and living [[Hedge|fence-row]]s.<ref name=Peery2018>{{Cite journal|last=Garcés‐Restrepo|first= M.F.|last2= Pauli|first2= J.N.|last3= Peery|first3= M.Z.|date= 2018|title= Natal dispersal of tree sloths in a human-dominated landscape: Implications for tropical biodiversity conservation|journal= Journal of Applied Ecology|volume= 55|issue= 5|pages= 2253–2262|doi= 10.1111/1365-2664.13138}}</ref> For the first few months after giving birth, mothers remain at just one or two trees, and guide their young. At about five to seven months of age, when the young have become more independent, mothers expand their resources and leave their young in new areas. During natal dispersion, three-toed sloths prefer tropical forests, often using riparian forest habitat to disperse.<ref>{{Cite journal|last=Garcés‐Restrepo|first=Mario F.|last2=Pauli|first2=Jonathan N.|last3=Peery|first3=M. Zachariah|date=2018|title=Natal dispersal of tree sloths in a human-dominated landscape: Implications for tropical biodiversity conservation|url=https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2664.13138|journal=Journal of Applied Ecology|language=en|volume=55|issue=5|pages=2253–2262|doi=10.1111/1365-2664.13138|issn=1365-2664}}</ref> The [[home range]] for mothers are larger than those of young. After separation, only the mothers use the cacao agro forest, but both use riparian forest. Different types of trees are used by both mother and young, which indicates that this agricultural matrix provides an important habitat type for these animals.<ref>{{cite journal | author = Ramirez, O.| year = 2011 | title = Temporal and spatial resource use by female three-toed sloths and their young in an agricultural landscape in Costa Rica | journal = Revista de Biologia Tropical | volume = 59 | issue = 4 | url=http://www.scielo.sa.cr/scielo.php?script=sci_abstract&pid=S0034-77442011000400027&lng=es&nrm=iso&tlng=en | pages = 1743–1755|display-authors=etal}}</ref> ===Dentition and skeleton=== Three-toed sloths have no [[incisor]] or [[canine (tooth)|canine]] teeth, just a set of peg-shaped cheek teeth that are not clearly divided into [[premolar]]s and [[molar (tooth)|molar]]s, and lack [[Homology (biology)|homology]] with those teeth in other mammals, thus are referred to as molariforms. The molariform dentition in three-toed sloths is simple and can be characterized as [[dentition|dental formula]] of: {{DentalFormula|upper=5|lower=4-5}}.<ref>{{cite book|last1=Ungar|first1=P.S.|title=Mammal Teeth: Origin, Evolution, and Diversity|date=2010|publisher=Johns Hopkins University Press|location=Baltimore, US|isbn=9780801899515|pages=145–6}}</ref> Three-toed sloths are unusual amongst the [[mammals]] in possessing as many as nine [[cervical vertebrae]], which may be due to mutations in the [[homeotic genes]].<ref>{{cite web|title=Sticking Their Necks out for Evolution: Why Sloths and Manatees Have Unusually Long (or Short) Necks|url=https://www.sciencedaily.com/releases/2011/05/110505212314.htm|work=May 6th 2011|publisher=Science Daily|accessdate=25 July 2013}}</ref> All other mammals have seven cervical vertebrae,<ref>{{cite journal |pmid=10327647 |author=Frietson Galis |year=1999 |title=Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes and Cancer |journal=Journal of Experimental Zoology |url=http://wwworm.biology.uh.edu/evodevo/lecture11/galis99.pdf |volume=285 |issue=1 |pages=19–26 |doi=10.1002/(SICI)1097-010X(19990415)285:1<19::AID-JEZ3>3.0.CO;2-Z |url-status=dead |archiveurl=https://web.archive.org/web/20041110200159/http://wwworm.biology.uh.edu/evodevo/lecture11/galis99.pdf |archivedate=2004-11-10 }}</ref> other than the two-toed sloth and the [[manatee]], which have only six. ==References== {{Reflist|30em}} ==External links== {{Commons|Bradypus}} {{Wikispecies|Bradypus}} *[http://passporttoknowledge.com/rainforest/ECOsystem/Animals/3toedsloth.html "Three-toed sloth." Passport to Knowledge. 21 Feb. 2009] {{Pilosa}} {{Taxonbar|from=Q185167}} {{DEFAULTSORT:Three-Toed Sloth}} [[Category:Sloths]] [[Category:Mammals described in 1758]] [[Category:Taxa named by Carl Linnaeus]]'