Three-toed sloth: Difference between revisions

Three-toed sloths
	Brown-throated three-toed sloth (Bradypus variegatus)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Pilosa
Superfamily:	Megatherioidea
Family:	Bradypodidae; Gray, 1821
Genus:	Bradypus; Linnaeus, 1758
Type species
	Bradypus tridactylus; Linnaeus, 1758
Species
	5, see text
	Green: B. pygmaeus, blue: B. tridactylus, red: B. variegatus, yellow: B. torquatus, orange: B. crinitus

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The three-toed or three-fingered sloths are arboreal neotropical mammals.^[2] They are the only members of the genus Bradypus (meaning "slow-footed") and the family Bradypodidae. The five living species of three-toed sloths are the brown-throated sloth, the maned sloth, the pale-throated sloth, the southern maned 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 folivorans, molecular studies place them nested within the sloth superfamily Megatherioidea, making them the only surviving members of that radiation.^[2]^[3]

Extant species

Scientific name	Common name	Distribution
B. pygmaeus	Pygmy three-toed sloth	Isla Escudo de Veraguas (Panama)
B. torquatus	Maned sloth	Atlantic coastal rainforest of southeastern Brazil
B. tridactylus	Pale-throated sloth	Part of northern South America, including Guyana, Suriname, French Guiana, eastern Venezuela and Brazil north of the Amazon River
B. variegatus	Brown-throated sloth	Central America and much of north and central South America, from Honduras through Colombia, Venezuela, Ecuador, eastern Peru, Bolivia and Brazil
B. crinitus	Southern maned sloth	Coastal Brazil in Rio de Janeiro and Espirito Santo.^[4]

Evolution

A study of mitochondrial cytochrome b and 16S rRNA sequences suggests that B. torquatus diverged from B. variegatus and 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.^[5]

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 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.^[6] 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 sloths.^[7]

Understanding of sloth phylogeny has recently been greatly revised by molecular studies, based on collagen^[3] and mitochondrial DNA^[2] sequences. These investigations consistently place three-toed sloths within Megatherioidea, close to Megalonyx, megatheriids and nothrotheriids, and two-toed sloths close to mylodontids, while moving the Caribbean sloths to a separate, basal branch of the sloth evolutionary tree.^[3]^[2] These results provide further strong support for the long-held belief that arboreality arose separately in the two genera via convergent paths.

Cladogram of sloths after Delsuc et al. 2019:^[2]

Folivora (sloths)

†Caribbean sloths

Mylodontoidea

	Two-toed sloths (Choelopus)

	†Mylodontidae (Mylodon)

Megatherioidea

†Megatheriidae (Megatherium)

	†Megalonychidae (Megalonyx)

	†Nothrotheriidae (Nothrotheriops)

Three-toed sloths (Bradypus)

Characteristics

Famously slow-moving, a sloth travels at an average speed of 0.24 km/h (0.15 mph).^[8] Three-toed sloths are about the size of a small dog or a large cat, with the head and body having a combined length of around 45 cm (18 in) and a weight of 3.5–4.5 kg (8–10 lb). Unlike the two-toed sloths, they also have short tails of 6–7 cm (2–3 in), and they have three clawed toes on each limb. All sloths have three digits on their hindlimbs; the difference is found in the number of digits on the forelimbs; thus they are sometimes referred to as three-fingered sloths.^[9] However, sloths are generally regarded as quadrupeds.

Behavior

Like the two-toed sloth, three-toed sloths are agile swimmers. They are still slow in trees.^[10] The muscles that sloths use to grip and produce a pulling motion are much more prominent than those that produce a pushing motion.^[11] This means that they struggle to support their body weight when walking on all four limbs, so traveling on the ground is a dangerous and laborious process.^[12]

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.^[13] 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.^[14]

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.^[14] It takes about a month for a single leaf to pass through its four-chambered stomach and digestive tract.^[15] Although they get most of their fluids from the leaves that they eat, they have been observed drinking directly from rivers.^[16] Because of their slow metabolism, they do not need to ingest many leaves on a daily basis, but when ambient temperatures are high, the symbiotic microbes and bacteria present in their gut will break down and ferment food at a faster rate.^[17] Conversely, when temperatures are lower, sloths will consume less, which is opposite to what has been observed in most other mammals.^[15] Only very few species of sloths are found at higher altitudes, and these are found to have thicker coats than those living in lower altitudes. Some of the extinct species of sloths were able to tolerate cooler temperatures, but researchers believe this was probably due to thicker fur, larger size, larger muscle mass, and more access to a constant food supply.^[18]

Their long, coarse fur often appears greenish, due not to pigment, but to algae growing on it. Sloths will consume the algae growing on their fur through the process of autogrooming, and the algae provides the sloths with carbohydrates and lipids, as an additional nutrition source.^[19] 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.^[20]

Three-toed sloths are predominantly diurnal, although they can be active at any hour of the day, while two-toed sloths are nocturnal.^[21]

Biology

Lifecycle

Members of this genus tend to live around 25 to 30 years, reaching sexual maturity at three to five years of age. Three-toed sloths do not have a mating season but breed year-round.

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.^[22] 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.^[23] Females give birth to a single young after a gestation period of around six months. The offspring cling to their mother's bellies for around nine months. They are 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 glands and dung middens.^[20]

The home ranges used by wild brown-throated three-toed sloths in Costa Rica include cacao, pasture, riparian forests, peri-urban areas, and living fence-rows.^[24] 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 while avoiding pastures and shade-grown cacao.^[25] The home range for mothers is larger than those of young. After separation, only the mothers use the cacao-growing forest, but both use riparian forests. 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.^[26]

Dentition and skeleton

Three-toed sloths have no incisor or canine teeth, just a set of peg-shaped cheek teeth that are not clearly divided into premolars and molars, and lack homology with those teeth in other mammals, and thus are referred to as molariforms. The molariform dentition in three-toed sloths is simple and can be characterized as dental formula of: 54-5.^[27]

Three-toed sloths are unusual amongst mammals in possessing as many as nine cervical vertebrae, which may be due to mutations in the homeotic genes.^[28] All other mammals have seven cervical vertebrae,^[29] other than the two-toed sloth and the manatee, which have only six.

Internal and external ecology

Three-toed sloths use their gut microbiome to break down the lignocellulose found in the leaves of the cecropia trees that they eat into short chain organic acids, which are then absorbed into the bloodstream to provide energy to the sloth.^[30] Firmicutes and Proteobacteria are the main bacterial phyla that dominate the sloth gut microbiome, which is less diverse than in many other herbivores. Not only are Firmicutes bacteria found in feces and digesta, but they are also found externally on the fur of sloths. Some research has found that Firmicutes bacteria in the genera Brevibacterium and Rothia can secrete antibiotic compounds that may provide protection from pathogenic bacteria.^[31]

In addition to the gut microbiome, three-toed sloths have a symbiotic relationship with the unique ecosystem that grows on their fur. ^[32] The ecosystem is home to everything from green algae, insects, and microbes. In particular, there is a proposed symbiosis between three-toed sloths and Trichophilus spp., a genus of green algae, as some Trichophilus spp. have only been found in sloth hair, suggesting that the algae may be passed from the mother to the offspring.^[33] The unique structure of sloth hair makes it the ideal place for algal growth due to its structural characteristics of cracks in the hairs and the ability for the hair to retain moisture. The algae has been found in the stomach of sloths, which may indicate that sloths are consuming the algae for some nutritional benefit, although the extent to which the algae provides dietary nutrients is still unclear.^[34] The algae may serve other purposes, such as insulation and facilitating growth of beneficial bacterial species,^[35] as well as providing the sloths with UV-protection, all in exchange for the habitat for growth provided by the sloth.^[33]

References

^ Gardner, A. L. (2005). "Order Pilosa". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 100–101. ISBN 978-0-8018-8221-0. OCLC 62265494.
^ ^a ^b ^c ^d ^e Delsuc, F.; Kuch, M.; Gibb, G.C.; Karpinski, E.; Hackenberger, D.; Szpak, P.; et al. (2019). "Ancient Mitogenomes reveal the evolutionary history and biogeography of sloths". Current Biology. 29 (12): 2031–2042.e6. Bibcode:2019CBio...29E2031D. doi:10.1016/j.cub.2019.05.043. hdl:11336/136908. PMID 31178321.
^ ^a ^b ^c Presslee, S.; Slater, G. J.; Pujos, F.; Forasiepi, A. M.; Fischer, R.; Molloy, K.; et al. (2019). "Palaeoproteomics resolves sloth relationships" (PDF). Nature Ecology & Evolution. 3 (7): 1121–1130. Bibcode:2019NatEE...3.1121P. doi:10.1038/s41559-019-0909-z. PMID 31171860. S2CID 174813630. Archived (PDF) from the original on 12 September 2020. Retrieved 18 September 2020.
^ Miranda, Flavia (February 2023). "Taxonomic revision of maned sloths, subgenus Bradypus (Scaeopus), Pilosa, Bradypodidae, with revalidation of Bradypus crinitus Gray, 1850". Journal of Mammalogy. 104 (1): 86–103. doi:10.1093/jmammal/gyac059.
^ de Moraes-Barros, N.; Silva, J. A. B.; Morgante, J. S. (2011-02-16). "Morphology, molecular phylogeny, and taxonomic inconsistencies in the study of Bradypus sloths (Pilosa: Bradypodidae)". Journal of Mammalogy. 92 (1): 86–100. doi:10.1644/10-MAMM-A-086.1.
^ Hoss, Matthias; Dilling, Amrei; Currant, Andrew; Paabo, Svante (9 Jan 1996). "Molecular phylogeny of the extinct ground sloth Mylodon darwinii". Proceedings of the National Academy of Sciences. 93 (1): 181–185. Bibcode:1996PNAS...93..181H. doi:10.1073/pnas.93.1.181. PMC 40202. PMID 8552600.
^ White, J.L.; MacPhee, R.D.E. (2001). "The sloths of the West Indies: a systematic and phylogenetic review". In Woods, C.A.; Sergile, F.E. (eds.). Biogeography of the West Indies: Patterns and perspectives. Boca Raton, FL / London, UK / New York, NY / Washington, DC: CRC Press. pp. 201–235. doi:10.1201/9781420039481-14. ISBN 978-0-8493-2001-9.
^ "Speed of Animals". infoplease.com.
^ 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
^ Three-toed Sloth, National Geographic.
^ Olson, Rachel A.; Glenn, Zachary D.; Cliffe, Rebecca N.; Butcher, Michael T. (2018-12-01). "Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)". Journal of Mammalian Evolution. 25 (4): 573–588. doi:10.1007/s10914-017-9411-z. ISSN 1573-7055. S2CID 22238582.
^ Keating, Ian D. (2018-01-01), Audacious Sloth, retrieved 2020-03-30
^ Olson, R.A.; Glenn, Z.D.; Cliffe, R.N.; Butcher, M.T. (2018-12-01). "Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)". Journal of Mammalian Evolution. 25 (4): 573–588. doi:10.1007/s10914-017-9411-z. S2CID 22238582.
^ ^a ^b Cliffe, R.N.; Avey-Arroyo, J.A.; Arroyo, F.J.; Holton, M.D.; Wilson, R.P. (2014-04-30). "Mitigating the squash effect: sloths breathe easily upside down". Biology Letters. 10 (4): 20140172. doi:10.1098/rsbl.2014.0172. PMC 4013704. PMID 24759371.
^ ^a ^b Cliffe, Rebecca N.; Haupt, Ryan J.; Avey-Arroyo, Judy A.; Wilson, Rory P. (2015-04-02). "Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus)". PeerJ. 3: e875. doi:10.7717/peerj.875. ISSN 2167-8359. PMC 4389270. PMID 25861559.
^ Cliffe, Rebecca N.; Haupt, Ryan J. (2018). "Hanging out for a drink". Frontiers in Ecology and the Environment. 16 (8): 446. Bibcode:2018FrEE...16..446C. doi:10.1002/fee.1955. ISSN 1540-9309.
^ Cliffe, R.N.; Haupt, R.J.; Avey-Arroyo, J.A.; Wilson, R.P. (2015-04-02). "Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus)". PeerJ. 3: e875. doi:10.7717/peerj.875. PMC 4389270. PMID 25861559.
^ Gilmore, D. P.; Da Costa, C. P.; Duarte, D. P. F. (January 2001). "Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses". Brazilian Journal of Medical and Biological Research. 34 (1): 9–25. doi:10.1590/S0100-879X2001000100002. ISSN 0100-879X. PMID 11151024.
^ Pauli, Jonathan N.; Mendoza, Jorge E.; Steffan, Shawn A.; Carey, Cayelan C.; Weimer, Paul J.; Peery, M. Zachariah (2014-03-07). "A syndrome of mutualism reinforces the lifestyle of a sloth". Proceedings of the Royal Society B: Biological Sciences. 281 (1778): 20133006. doi:10.1098/rspb.2013.3006. ISSN 0962-8452. PMC 3906947. PMID 24452028.
^ ^a ^b Dickman, Christopher R. (1984). Macdonald, D. (ed.). The Encyclopedia of Mammals. New York: Facts on File. pp. 776–779. ISBN 0-87196-871-1.
^ Eisenberg, John F.; Redford, Kent H. (May 15, 2000). Mammals of the Neotropics, Volume 3: The Central Neotropics: Ecuador, Peru, Bolivia, Brazil. University of Chicago Press. pp. 624 (see pp. 94–95, 97). ISBN 978-0-226-19542-1. OCLC 493329394.
^ Gilmore, D.P.; et al. (2000). "An update on the physiology of two- and three-toed sloths". Brazilian Journal of Medical and Biological Research. 33 (2): 129–146. doi:10.1590/S0100-879X2000000200001. PMID 10657054.
^ Pauli, J.N. & Peery, M.Z. (2012). "Unexpected strong polygyny in the brown-throated three-toed sloth". PLOS ONE. 7 (12): e51389. Bibcode:2012PLoSO...751389P. doi:10.1371/journal.pone.0051389. PMC 3526605. PMID 23284687.
^ Garcés-Restrepo, M.F.; Pauli, J.N.; Peery, M.Z. (2018). "Natal dispersal of tree sloths in a human-dominated landscape: Implications for tropical biodiversity conservation". Journal of Applied Ecology. 55 (5): 2253–2262. Bibcode:2018JApEc..55.2253G. doi:10.1111/1365-2664.13138.
^ Garcés-Restrepo, Mario F.; Pauli, Jonathan N.; Peery, M. Zachariah (2018). "Natal dispersal of tree sloths in a human-dominated landscape: Implications for tropical biodiversity conservation". Journal of Applied Ecology. 55 (5): 2253–2262. Bibcode:2018JApEc..55.2253G. doi:10.1111/1365-2664.13138. ISSN 1365-2664.
^ Ramirez, O.; et al. (2011). "Temporal and spatial resource use by female three-toed sloths and their young in an agricultural landscape in Costa Rica". Revista de Biología Tropical. 59 (4): 1743–1755. PMID 22208090.
^ Ungar, P.S. (2010). Mammal Teeth: Origin, Evolution, and Diversity. Baltimore, US: Johns Hopkins University Press. pp. 145–6. ISBN 9780801899515.
^ "Sticking Their Necks out for Evolution: Why Sloths and Manatees Have Unusually Long (or Short) Necks". May 6th 2011. Science Daily. Retrieved 25 July 2013.
^ Frietson Galis (1999). "Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes and Cancer" (PDF). Journal of Experimental Zoology. 285 (1): 19–26. Bibcode:1999JEZ...285...19G. doi:10.1002/(SICI)1097-010X(19990415)285:1<19::AID-JEZ3>3.0.CO;2-Z. PMID 10327647. Archived from the original (PDF) on 2004-11-10.
^ Dill-McFarland, Kimberly A.; Weimer, Paul J.; Pauli, Jonathan N.; Peery, M. Zachariah; Suen, Garret (2015-09-10). "Diet specialization selects for an unusual and simplified gut microbiota in two- and three-toed sloths". Environmental Microbiology. 18 (5): 1391–1402. doi:10.1111/1462-2920.13022. ISSN 1462-2912. PMID 26271635.
^ Rojas-Gätjens, Diego; Valverde-Madrigal, Katherine S.; Rojas-Jimenez, Keilor; Pereira, Reinaldo; Avey-Arroyo, Judy; Chavarría, Max (2022-04-08). "Antibiotic-producing Micrococcales govern the microbiome that inhabits the fur of two- and three-toed sloths". doi:10.1101/2022.04.08.486316. S2CID 249096251. Retrieved 2023-12-01.
^ Kaup, Maya; Trull, Sam; Hom, Erik F. Y. (2021-06-26). "On the move: sloths and their epibionts as model mobile ecosystems". Biological Reviews. 96 (6): 2638–2660. doi:10.1111/brv.12773. ISSN 1464-7931. PMC 9290738. PMID 34309191.
^ ^a ^b Suutari, Milla; Majaneva, Markus; Fewer, David P.; Voirin, Bryson; Aiello, Annette; Friedl, Thomas; Chiarello, Adriano G.; Blomster, Jaanika (2010-03-30). "Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with Trichophilus welckeri(Chlorophyta, Ulvophyceae)". BMC Evolutionary Biology. 10 (1): 86. Bibcode:2010BMCEE..10...86S. doi:10.1186/1471-2148-10-86. ISSN 1471-2148. PMC 2858742. PMID 20353556.
^ Pauli, Jonathan N.; Mendoza, Jorge E.; Steffan, Shawn A.; Carey, Cayelan C.; Weimer, Paul J.; Peery, M. Zachariah (2014-03-07). "A syndrome of mutualism reinforces the lifestyle of a sloth". Proceedings of the Royal Society B: Biological Sciences. 281 (1778): 20133006. doi:10.1098/rspb.2013.3006. ISSN 0962-8452. PMC 3906947. PMID 24452028.
^ Montgomery, G. Gene, ed. (1978). The Ecology of arboreal folivores: a symposium held at the Conservation and Research Center, National Zoological Park, Smithsonian Institution, May 29-31, 1975. Symposia of the National Zoological Park. Washington: Smithsonian Institution Press. ISBN 978-0-87474-646-4.

External links

"Three-toed sloth." Passport to Knowledge. 21 Feb. 2009

[msw3-1] Gardner, A. L. (2005). "Order Pilosa". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. pp. 100–101. ISBN 978-0-8018-8221-0. OCLC 62265494.

[Delsuc2019-2] Delsuc, F.; Kuch, M.; Gibb, G.C.; Karpinski, E.; Hackenberger, D.; Szpak, P.; et al. (2019). "Ancient Mitogenomes reveal the evolutionary history and biogeography of sloths". Current Biology. 29 (12): 2031–2042.e6. Bibcode:2019CBio...29E2031D. doi:10.1016/j.cub.2019.05.043. hdl:11336/136908. PMID 31178321.

[Presslee2019-3] Presslee, S.; Slater, G. J.; Pujos, F.; Forasiepi, A. M.; Fischer, R.; Molloy, K.; et al. (2019). "Palaeoproteomics resolves sloth relationships" (PDF). Nature Ecology & Evolution. 3 (7): 1121–1130. Bibcode:2019NatEE...3.1121P. doi:10.1038/s41559-019-0909-z. PMID 31171860. S2CID 174813630. Archived (PDF) from the original on 12 September 2020. Retrieved 18 September 2020.

[4] Miranda, Flavia (February 2023). "Taxonomic revision of maned sloths, subgenus Bradypus (Scaeopus), Pilosa, Bradypodidae, with revalidation of Bradypus crinitus Gray, 1850". Journal of Mammalogy. 104 (1): 86–103. doi:10.1093/jmammal/gyac059.

[de_Moraes-Barros2011-5] Moraes-Barros, N.; Silva, J. A. B.; Morgante, J. S. (2011-02-16). "Morphology, molecular phylogeny, and taxonomic inconsistencies in the study of Bradypus sloths (Pilosa: Bradypodidae)". Journal of Mammalogy. 92 (1): 86–100. doi:10.1644/10-MAMM-A-086.1.

[Hoss-6] Hoss, Matthias; Dilling, Amrei; Currant, Andrew; Paabo, Svante (9 Jan 1996). "Molecular phylogeny of the extinct ground sloth Mylodon darwinii". Proceedings of the National Academy of Sciences. 93 (1): 181–185. Bibcode:1996PNAS...93..181H. doi:10.1073/pnas.93.1.181. PMC 40202. PMID 8552600.

[White-7] White, J.L.; MacPhee, R.D.E. (2001). "The sloths of the West Indies: a systematic and phylogenetic review". In Woods, C.A.; Sergile, F.E. (eds.). Biogeography of the West Indies: Patterns and perspectives. Boca Raton, FL / London, UK / New York, NY / Washington, DC: CRC Press. pp. 201–235. doi:10.1201/9781420039481-14. ISBN 978-0-8493-2001-9.

[infoplease-8] "Speed of Animals". infoplease.com.

[9] 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

[National_Geographic-10] Three-toed Sloth, National Geographic.

[11] Olson, Rachel A.; Glenn, Zachary D.; Cliffe, Rebecca N.; Butcher, Michael T. (2018-12-01). "Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)". Journal of Mammalian Evolution. 25 (4): 573–588. doi:10.1007/s10914-017-9411-z. ISSN 1573-7055. S2CID 22238582.

[12] Keating, Ian D. (2018-01-01), Audacious Sloth, retrieved 2020-03-30

[Olson2018-13] Olson, R.A.; Glenn, Z.D.; Cliffe, R.N.; Butcher, M.T. (2018-12-01). "Architectural Properties of Sloth Forelimb Muscles (Pilosa: Bradypodidae)". Journal of Mammalian Evolution. 25 (4): 573–588. doi:10.1007/s10914-017-9411-z. S2CID 22238582.

[Cliffe2014-14] Cliffe, R.N.; Avey-Arroyo, J.A.; Arroyo, F.J.; Holton, M.D.; Wilson, R.P. (2014-04-30). "Mitigating the squash effect: sloths breathe easily upside down". Biology Letters. 10 (4): 20140172. doi:10.1098/rsbl.2014.0172. PMC 4013704. PMID 24759371.

[ReferenceA-15] Cliffe, Rebecca N.; Haupt, Ryan J.; Avey-Arroyo, Judy A.; Wilson, Rory P. (2015-04-02). "Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus)". PeerJ. 3: e875. doi:10.7717/peerj.875. ISSN 2167-8359. PMC 4389270. PMID 25861559.

[16] Cliffe, Rebecca N.; Haupt, Ryan J. (2018). "Hanging out for a drink". Frontiers in Ecology and the Environment. 16 (8): 446. Bibcode:2018FrEE...16..446C. doi:10.1002/fee.1955. ISSN 1540-9309.

[Cliffe2015-17] Cliffe, R.N.; Haupt, R.J.; Avey-Arroyo, J.A.; Wilson, R.P. (2015-04-02). "Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus)". PeerJ. 3: e875. doi:10.7717/peerj.875. PMC 4389270. PMID 25861559.

[18] Gilmore, D. P.; Da Costa, C. P.; Duarte, D. P. F. (January 2001). "Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses". Brazilian Journal of Medical and Biological Research. 34 (1): 9–25. doi:10.1590/S0100-879X2001000100002. ISSN 0100-879X. PMID 11151024.

[19] Pauli, Jonathan N.; Mendoza, Jorge E.; Steffan, Shawn A.; Carey, Cayelan C.; Weimer, Paul J.; Peery, M. Zachariah (2014-03-07). "A syndrome of mutualism reinforces the lifestyle of a sloth". Proceedings of the Royal Society B: Biological Sciences. 281 (1778): 20133006. doi:10.1098/rspb.2013.3006. ISSN 0962-8452. PMC 3906947. PMID 24452028.

[EoM-20] Dickman, Christopher R. (1984). Macdonald, D. (ed.). The Encyclopedia of Mammals. New York: Facts on File. pp. 776–779. ISBN 0-87196-871-1.

[Eisenberg2000-21] Eisenberg, John F.; Redford, Kent H. (May 15, 2000). Mammals of the Neotropics, Volume 3: The Central Neotropics: Ecuador, Peru, Bolivia, Brazil. University of Chicago Press. pp. 624 (see pp. 94–95, 97). ISBN 978-0-226-19542-1. OCLC 493329394.

[22] Gilmore, D.P.; et al. (2000). "An update on the physiology of two- and three-toed sloths". Brazilian Journal of Medical and Biological Research. 33 (2): 129–146. doi:10.1590/S0100-879X2000000200001. PMID 10657054.

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@@ Line 2: / Line 2: @@
 {{Automatic taxobox
 | name = Three-toed sloths<ref name=msw3>{{MSW3 Pilosa | id = 11800004 | pages=100–101}}</ref>
-| image = Perezoso La Mochila.jpg
+| image = Bradypus.jpg
-| image_caption = [[Pygmy three-toed sloth]] (''Bradypus pygmaeus'')
+| image_caption = [[Brown-throated three-toed sloth]] (''Bradypus variegatus'')
 | taxon = Bradypus
 | authority = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
@@ Line 13: / Line 13: @@
 | subdivision = 5, see [[#Extant species|text]]
 | range_map = Three-toed sloth range.jpg
-| range_map_caption = Distribution of the Bradypus's species (Green: ''B. pygmaeus '',blue: ''B. tridactylus'',red: ''B. variegatus '',yellow: ''B. torquatus '',Orange: ''B. crinitus '')
+| range_map_caption = Green: ''B. pygmaeus'', blue: ''B. tridactylus'', red: ''B. variegatus'', yellow: ''B. torquatus'', orange: ''B. crinitus''
 }}
-The '''three-toed sloths''' are [[arboreal locomotion|arboreal]] [[neotropical]] mammals.<ref name="Delsuc2019" /> They are the only members of the [[genus]] '''''Bradypus''''' (meaning "slow-footed") and the [[family (biology)|family]] '''Bradypodidae'''. The five living species of three-toed sloths are the [[brown-throated sloth]], the [[maned sloth]], the [[pale-throated sloth]], the [[southern maned 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="Delsuc2019" /><ref name="Presslee2019" />
+The '''three-toed''' or '''three-fingered sloths''' are [[arboreal locomotion|arboreal]] [[neotropical]] mammals.<ref name="Delsuc2019" /> They are the only members of the [[genus]] '''''Bradypus''''' (meaning "slow-footed") and the [[family (biology)|family]] '''Bradypodidae'''. The five living species of three-toed sloths are the [[brown-throated sloth]], the [[maned sloth]], the [[pale-throated sloth]], the [[southern maned 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 [[evolutionary radiation|radiation]].<ref name="Delsuc2019" /><ref name="Presslee2019" />
 ==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:Bradypus pygmaeus.jpg|120px]] || ''B. pygmaeus'' || [[Pygmy three-toed sloth]]|| [[Isla Escudo de Veraguas]] (Panama)
 |-
-| [[File:PisaMammalGallery (6).JPG|120px]] || ''B. torquatus''|| [[Maned three-toed sloth]] ||  Atlantic coastal rainforest of southeastern Brazil
+| [[File:PisaMammalGallery (6).JPG|120px]] || ''B. torquatus''|| [[Maned sloth]] ||  Atlantic coastal rainforest of southeastern Brazil
 |-
-| [[File:Bradypus tridactylus.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:Bradypus tridactylus.jpg|120px]] || ''B. tridactylus'' || [[Pale-throated 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
+| [[File:Bicho-preguiça 3.jpg|120px]] || ''B. variegatus''|| [[Brown-throated sloth]] || Central America and much of north and central South America, from Honduras through Colombia, Venezuela, Ecuador, eastern Peru, Bolivia and Brazil
 |-
 | [[File:Bradypus torquatus 47880997.jpg|120px]] || ''B. crinitus''|| [[Southern maned sloth]] || Coastal Brazil in [[Rio de Janeiro]] and [[Espírito Santo|Espirito Santo]].<ref>{{cite journal |last1=Miranda |first1=Flavia |title=Taxonomic revision of maned sloths, subgenus Bradypus (Scaeopus), Pilosa, Bradypodidae, with revalidation of Bradypus crinitus Gray, 1850 |journal=Journal of Mammalogy |date=February 2023 |volume=104 |issue=1 |pages=86–103 |doi=10.1093/jmammal/gyac059}}</ref>
-|-
 |}
@@ Line 58: / Line 56: @@
 </ref>
-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">
+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. |display-authors=6 |year=2019 |title=Palaeoproteomics resolves sloth relationships |journal=Nature Ecology & Evolution |volume=3 |issue=7 |pages=1121–1130 |doi=10.1038/s41559-019-0909-z |pmid=31171860 |bibcode=2019NatEE...3.1121P |s2cid=174813630 |url=http://eprints.whiterose.ac.uk/147061/1/5426_3_merged_1554730549.pdf |access-date=18 September 2020 |archive-date=12 September 2020 |archive-url=https://web.archive.org/web/20200912204649/http://eprints.whiterose.ac.uk/147061/1/5426_3_merged_1554730549.pdf |url-status=live}}</ref><ref name="Delsuc2019">
-{{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.
- |last25= Collins  |first25= M.      |last26= MacPhee   |first26= R.D.E.
- |last24= Penkman  |first24= K.  |author24-link=Kirsty Penkman
- |display-authors=6
- |year= 2019
- |title= Palaeoproteomics resolves sloth relationships
- |journal=Nature Ecology & Evolution
- |volume= 3  |issue= 7  |pages= 1121–1130
- |doi= 10.1038/s41559-019-0909-z |pmid= 31171860|s2cid= 174813630
- }}
-</ref><ref name="Delsuc2019">
 {{cite journal
  |last1= Delsuc     |first1= F.    |last2= Kuch      |first2= M.
@@ Line 96: / Line 71: @@
  |volume= 29  |issue= 12  |pages= 2031–2042.e6
  |doi= 10.1016/j.cub.2019.05.043 |doi-access= free |pmid= 31178321
- |url= https://www.researchgate.net/publication/333647272
+ |bibcode= 2019CBio...29E2031D |url= https://www.researchgate.net/publication/333647272
 |hdl= 11336/136908|hdl-access= free}}
 </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.
+Cladogram of sloths after Delsuc et al. 2019:<ref name="Delsuc2019" />{{clade|{{clade
-The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig.&nbsp;4 of Presslee ''et al''., 2019).<ref name="Presslee2019"/>
+|1={{extinct}}[[Megalocnidae|Caribbean sloths]]
-{{clade
+|2={{clade
+|label1=Mylodontoidea
-| style = font-size: 100%;line-height:100%
-| label1 = &nbsp; [[Folivora]] &nbsp;
 |1={{clade
+|1=[[Two-toed sloths]] ''(Choelopus)''
-   |sublabel1= {{big|&nbsp;}}
+|2={{extinct}}[[Mylodontidae]] (''[[Mylodon]]'')
-   |1={{clade
-      |label1 =  &nbsp; {{extinct}} [[Megalocnidae]] &nbsp;
-      |sublabel1 = &nbsp; {{small| (Caribbean sloths) }} &nbsp;
-      |1= &nbsp; (four extinct spp.)
-      }}
-   |2={{clade
-     | 1={{clade
-<!--     |grouplabel1={{clade label|'''Mylodontoidea'''|color=green|width=7.5em}}
-         |bar1=green  -->
-         |label1=&nbsp; Mylodontoidea &nbsp;
-         |1={{clade
-            |1={{clade
-            |label1= &nbsp; {{extinct}} [[Scelidotheriidae]]
-            |1=&nbsp;
-            }}
-         |2={{clade
-          |label1 = <br/> &nbsp; {{extinct}} [[Mylodontidae]]
-          |1=&nbsp;
-            |label2=&nbsp; [[Choloepodidae]] &nbsp;
-            |sublabel2=&nbsp; {{small| (two-fingered sloths) }} &nbsp;
-            |2={{clade
-             |label1 =&nbsp; ''[[Choloepus]]'' &nbsp;
-             |sublabel1={{big| &nbsp; }}
-             |1=&nbsp; [[Choloepus|(two living spp.)]]
-             }}
-          }}
-      }}
-<!--   |grouplabelstyle1=vertical-align:left;
-       |grouplabel2={{clade label|'''Megatherioidea'''|color=red|width=8em}}
-       |bar2=red  -->
-       |label2=&nbsp; Megatherioidea &nbsp;
-       |2={{clade
-          |1={{clade
-             |label1 = &nbsp; {{extinct}} [[Megalonychidae]] &nbsp;
-             |1=&nbsp; {{extinct}} ''[[Megalonyx|Megalonyx jeffersoni]]''
-             |label2 = &nbsp; Bradypodidae &nbsp;
-             |sublabel2 =&nbsp; {{small| (three fingered sloths) }} &nbsp;
-             |2={{clade
-                |label1=&nbsp; ''[[Bradypus]]'' &nbsp;
-                |sublabel1={{small|&nbsp;}}
-                |1={{clade
-                   |1=&nbsp; ''[[Bradypus torquatus|B. torquatus]]''
-                      |2={{clade
-                         |1=&nbsp; ''[[Bradypus pygmaeus|B. pygmaeus]]''
-                         |2={{clade
-                            |1=&nbsp; ''[[Bradypus tridactylus|B. tridactylus]]''
-                            |2=&nbsp; ''[[Bradypus variegatus|B. variegatus]]''
-                            }}
-                          }}
-                   }}
-               }}
-            }}
-          |2={{clade
-             |label1 = &nbsp; {{extinct}} [[Nothrotheriidae]]
-             |1=&nbsp; {{extinct}} ''[[Nothrotheriops|Nothrotheriops shastensis]]''
-             |label2 = &nbsp; {{extinct}} [[Megatheriidae]] &nbsp;
-             |2=&nbsp; {{extinct}} ''[[Megatherium|Megatherium americanum]]''
-             }}
-        }}
-      }}
-    }}
-  }}
 }}
+|label2=Megatherioidea
+|2={{clade
+|1={{extinct}}[[Megatheriidae]] (''[[Megatherium]]'')
+|2={{clade
+|1={{clade
+|1={{extinct}}[[Megalonychidae]] (''[[Megalonyx]]'')
+|2={{extinct}}[[Nothrotheriidae]] (''[[Nothrotheriops]]'')
+}}
+|2='''Three-toed sloths''' (''Bradypus'')
+}}}}}}}}|label1=[[Folivora]] (sloths)}}{{clear}}
 ==Characteristics==
@@ Line 181: / Line 103: @@
 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|last1= Olson|first1= R.A.|last2= Glenn|first2= Z.D.|last3= Cliffe|first3= R.N.|author3-link= Rebecca Cliffe|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|s2cid= 22238582}}</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|last1= Cliffe|first1= R.N.|author1-link= Rebecca Cliffe|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 its four-chambered stomach and digestive tract.<ref name="ReferenceA">{{Cite journal|last1=Cliffe|first1=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)|journal=PeerJ|volume=3|pages=e875|doi=10.7717/peerj.875|issn=2167-8359|pmc=4389270|pmid=25861559 |doi-access=free }}</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|last1=Cliffe|first1=Rebecca N.|last2=Haupt|first2=Ryan J.|date=2018|title=Hanging out for a drink|journal=Frontiers in Ecology and the Environment|language=en|volume=16|issue=8|pages=446|doi=10.1002/fee.1955|issn=1540-9309|doi-access=free}}</ref> Because of their slow metabolism, they do not need to ingest many leaves on a daily basis, but 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|last1= Cliffe|first1= 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|pages= e875|doi= 10.7717/peerj.875|pmc= 4389270|pmid= 25861559|doi-access= free}}</ref> Conversely, when temperatures are lower, sloths will consume less, which is opposite to what has been observed in most other mammals.<ref name="ReferenceA"/> Only very few species of sloths are found at higher altitudes, and these are found to have thicker coats than those living in lower altitudes. Some of the extinct species of sloths were able to tolerate cooler temperatures, but researchers believe this was probably due to thicker fur, larger size, larger muscle mass, and more access to a constant food supply.<ref>{{Cite journal |last1=Gilmore |first1=D. P. |last2=Da Costa |first2=C. P. |last3=Duarte |first3=D. P. F. |date=January 2001 |title=Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses |journal=Brazilian Journal of Medical and Biological Research |language=en |volume=34 |issue=1 |pages=9–25 |doi=10.1590/S0100-879X2001000100002 |pmid=11151024 |issn=0100-879X|doi-access=free }}</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 its four-chambered stomach and digestive tract.<ref name="ReferenceA">{{Cite journal|last1=Cliffe|first1=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)|journal=PeerJ|volume=3|pages=e875|doi=10.7717/peerj.875|issn=2167-8359|pmc=4389270|pmid=25861559 |doi-access=free }}</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|last1=Cliffe|first1=Rebecca N.|last2=Haupt|first2=Ryan J.|date=2018|title=Hanging out for a drink|journal=Frontiers in Ecology and the Environment|language=en|volume=16|issue=8|pages=446|doi=10.1002/fee.1955|issn=1540-9309|doi-access=free|bibcode=2018FrEE...16..446C }}</ref> Because of their slow metabolism, they do not need to ingest many leaves on a daily basis, but 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|last1= Cliffe|first1= 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|pages= e875|doi= 10.7717/peerj.875|pmc= 4389270|pmid= 25861559|doi-access= free}}</ref> Conversely, when temperatures are lower, sloths will consume less, which is opposite to what has been observed in most other mammals.<ref name="ReferenceA"/> Only very few species of sloths are found at higher altitudes, and these are found to have thicker coats than those living in lower altitudes. Some of the extinct species of sloths were able to tolerate cooler temperatures, but researchers believe this was probably due to thicker fur, larger size, larger muscle mass, and more access to a constant food supply.<ref>{{Cite journal |last1=Gilmore |first1=D. P. |last2=Da Costa |first2=C. P. |last3=Duarte |first3=D. P. F. |date=January 2001 |title=Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses |journal=Brazilian Journal of Medical and Biological Research |language=en |volume=34 |issue=1 |pages=9–25 |doi=10.1590/S0100-879X2001000100002 |pmid=11151024 |issn=0100-879X|doi-access=free }}</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.
+Their long, coarse fur often appears greenish, due not to pigment, but to algae growing on it. Sloths will consume the algae growing on their fur through the process of autogrooming, and the algae provides the sloths with carbohydrates and lipids, as an additional nutrition source.<ref>{{Cite journal |last1=Pauli |first1=Jonathan N. |last2=Mendoza |first2=Jorge E. |last3=Steffan |first3=Shawn A. |last4=Carey |first4=Cayelan C. |last5=Weimer |first5=Paul J. |last6=Peery |first6=M. Zachariah |date=2014-03-07 |title=A syndrome of mutualism reinforces the lifestyle of a sloth |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=281 |issue=1778 |pages=20133006 |doi=10.1098/rspb.2013.3006 |issn=0962-8452 |pmc=3906947 |pmid=24452028}}</ref> 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
@@ Line 198: / Line 120: @@
 ===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 maturity 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 of 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/>
+Members of this genus tend to live around 25 to 30 years, reaching sexual maturity at three to five years of age. Three-toed sloths do not have a mating season but breed year-round.
-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| doi-access = free }}</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.  |name-list-style=amp | 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 |doi-access=free }}</ref>
+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| doi-access = free }}</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.  |name-list-style=amp | 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 |doi-access=free }}</ref>  Females give birth to a single young after a [[gestation]] period of 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/>
-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|last1=Garcés-Restrepo|first1= 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|doi-access= free}}</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 while avoiding pastures and shade-grown cacao.<ref>{{Cite journal|last1=Garcés-Restrepo|first1=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|journal=Journal of Applied Ecology|language=en|volume=55|issue=5|pages=2253–2262|doi=10.1111/1365-2664.13138|issn=1365-2664|doi-access=free}}</ref> The [[home range]] for mothers is larger than those of young. After separation, only the mothers use the cacao-growing forest, but both use riparian forests. 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 Biología 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| pmid = 22208090 |display-authors=etal}}</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|last1=Garcés-Restrepo|first1= 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|doi-access= free|bibcode= 2018JApEc..55.2253G}}</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 while avoiding pastures and shade-grown cacao.<ref>{{Cite journal|last1=Garcés-Restrepo|first1=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|journal=Journal of Applied Ecology|language=en|volume=55|issue=5|pages=2253–2262|doi=10.1111/1365-2664.13138|issn=1365-2664|doi-access=free|bibcode=2018JApEc..55.2253G }}</ref> The [[home range]] for mothers is larger than those of young. After separation, only the mothers use the cacao-growing forest, but both use riparian forests. 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 Biología 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| pmid = 22208090 |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, and 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 [[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|access-date=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 |archive-url=https://web.archive.org/web/20041110200159/http://wwworm.biology.uh.edu/evodevo/lecture11/galis99.pdf |archive-date=2004-11-10 }}</ref> other than the two-toed sloth and the [[manatee]], which have only six.
+Three-toed sloths are unusual amongst [[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|access-date=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 |bibcode=1999JEZ...285...19G |url-status=dead |archive-url=https://web.archive.org/web/20041110200159/http://wwworm.biology.uh.edu/evodevo/lecture11/galis99.pdf |archive-date=2004-11-10 }}</ref> other than the two-toed sloth and the [[manatee]], which have only six.
+== Internal and external ecology ==
+Three-toed sloths use their gut [[microbiome]] to break down the [[Lignocellulosic biomass|lignocellulose]] found in the leaves of the [[cecropia]] trees that they eat into short chain organic acids, which are then absorbed into the bloodstream to provide energy to the sloth.<ref>{{Cite journal |last1=Dill-McFarland |first1=Kimberly A. |last2=Weimer |first2=Paul J. |last3=Pauli |first3=Jonathan N. |last4=Peery |first4=M. Zachariah |last5=Suen |first5=Garret |date=2015-09-10 |title=Diet specialization selects for an unusual and simplified gut microbiota in two- and three-toed sloths |url=http://dx.doi.org/10.1111/1462-2920.13022 |journal=Environmental Microbiology |volume=18 |issue=5 |pages=1391–1402 |doi=10.1111/1462-2920.13022 |pmid=26271635 |issn=1462-2912}}</ref> [[Firmicutes]] and [[Proteobacteria]] are the main bacterial phyla that dominate the sloth gut microbiome, which is less diverse than in many other herbivores. Not only are Firmicutes bacteria found in feces and digesta, but they are also found externally on the fur of sloths. Some research has found that Firmicutes bacteria in the genera ''[[Brevibacterium]]'' and ''[[Rothia (bacterium)|Rothia]]'' can secrete antibiotic compounds that may provide protection from pathogenic bacteria.<ref>{{Cite web |last1=Rojas-Gätjens |first1=Diego |last2=Valverde-Madrigal |first2=Katherine S. |last3=Rojas-Jimenez |first3=Keilor |last4=Pereira |first4=Reinaldo |last5=Avey-Arroyo |first5=Judy |last6=Chavarría |first6=Max |date=2022-04-08 |title=Antibiotic-producing Micrococcales govern the microbiome that inhabits the fur of two- and three-toed sloths |url=http://dx.doi.org/10.1101/2022.04.08.486316 |access-date=2023-12-01 |doi=10.1101/2022.04.08.486316 |s2cid=249096251 }}</ref>
+In addition to the gut microbiome, three-toed sloths have a symbiotic relationship with the unique ecosystem that grows on their fur. <ref>{{Cite journal |last1=Kaup |first1=Maya |last2=Trull |first2=Sam |last3=Hom |first3=Erik F. Y. |date=2021-06-26 |title=On the move: sloths and their epibionts as model mobile ecosystems |journal=Biological Reviews |language=en |volume=96 |issue=6 |pages=2638–2660 |doi=10.1111/brv.12773 |issn=1464-7931 |pmc=9290738 |pmid=34309191}}</ref> The ecosystem is home to everything from green algae, insects, and microbes. In particular, there is a proposed symbiosis between three-toed sloths and ''[[Trichophilus]]'' spp., a genus of green algae, as some ''Trichophilus'' spp. have only been found in sloth hair, suggesting that the algae may be passed from the mother to the offspring.<ref name=":0">{{Cite journal |last1=Suutari |first1=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=2010-03-30 |title=Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with Trichophilus welckeri(Chlorophyta, Ulvophyceae) |journal=BMC Evolutionary Biology |volume=10 |issue=1 |pages=86 |doi=10.1186/1471-2148-10-86 |doi-access=free |issn=1471-2148 |pmc=2858742 |pmid=20353556|bibcode=2010BMCEE..10...86S }}</ref> The unique structure of sloth hair makes it the ideal place for algal growth due to its structural characteristics of cracks in the hairs and the ability for the hair to retain moisture. The algae has been found in the stomach of sloths, which may indicate that sloths are consuming the algae for some nutritional benefit, although the extent to which the algae provides dietary nutrients is still unclear.<ref>{{Cite journal |last1=Pauli |first1=Jonathan N. |last2=Mendoza |first2=Jorge E. |last3=Steffan |first3=Shawn A. |last4=Carey |first4=Cayelan C. |last5=Weimer |first5=Paul J. |last6=Peery |first6=M. Zachariah |date=2014-03-07 |title=A syndrome of mutualism reinforces the lifestyle of a sloth |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=281 |issue=1778 |pages=20133006 |doi=10.1098/rspb.2013.3006 |issn=0962-8452 |pmc=3906947 |pmid=24452028}}</ref> The algae may serve other purposes, such as insulation and facilitating growth of beneficial bacterial species,<ref>{{Cite book |title=The Ecology of arboreal folivores: a symposium held at the Conservation and Research Center, National Zoological Park, Smithsonian Institution, May 29-31, 1975 |date=1978 |publisher=Smithsonian Institution Press |isbn=978-0-87474-646-4 |editor-last=Montgomery |editor-first=G. Gene |series=Symposia of the National Zoological Park |location=Washington}}</ref> as well as providing the sloths with UV-protection, all in exchange for the habitat for growth provided by the sloth.<ref name=":0" />
-== Microbial ecology ==
-Three-toed sloths use their gut [[microbiome]] to break down the [[Lignocellulosic biomass|lignocellulose]] found in the leaves of the [[cecropia]] trees that they eat into short chain organic acids, which is then absorbed into the bloodstream to provide energy to the sloth.<ref>{{Cite journal |last1=Dill-McFarland |first1=Kimberly A. |last2=Weimer |first2=Paul J. |last3=Pauli |first3=Jonathan N. |last4=Peery |first4=M. Zachariah |last5=Suen |first5=Garret |date=2015-09-10 |title=Diet specialization selects for an unusual and simplified gut microbiota in two- and three-toed sloths |url=http://dx.doi.org/10.1111/1462-2920.13022 |journal=Environmental Microbiology |volume=18 |issue=5 |pages=1391–1402 |doi=10.1111/1462-2920.13022 |issn=1462-2912}}</ref> [[Firmicutes]] and [[Proteobacteria]] are the main bacterial phyla that dominate the sloth gut microbiome, which is less diverse than in many other herbivores. Not only are Firmicutes bacteria found in feces and digesta, but they are also found externally on the fur of sloths. Some research has found that Firmicutes bacteria in the genera ''[[Brevibacterium]]'' and ''[[Rothia (bacterium)|Rothia]]'' can secrete antibiotic compounds that may provide protection from pathogenic bacteria.<ref>{{Cite web |last1=Rojas-Gätjens |first1=Diego |last2=Valverde-Madrigal |first2=Katherine S. |last3=Rojas-Jimenez |first3=Keilor |last4=Pereira |first4=Reinaldo |last5=Avey-Arroyo |first5=Judy |last6=Chavarría |first6=Max |date=2022-04-08 |title=Antibiotic-producing Micrococcales govern the microbiome that inhabits the fur of two- and three-toed sloths |url=http://dx.doi.org/10.1101/2022.04.08.486316 |access-date=2023-12-01 |doi=10.1101/2022.04.08.486316 }}</ref>
 ==References==