Bradypus tridactylus (*)
Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Megaclassis: Osteichthyes
Cladus: Sarcopterygii
Cladus: Rhipidistia
Cladus: Tetrapodomorpha
Cladus: Eotetrapodiformes
Cladus: Elpistostegalia
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Cladus: Synapsida
Cladus: Eupelycosauria
Cladus: Sphenacodontia
Cladus: Sphenacodontoidea
Cladus: Therapsida
Cladus: Theriodontia
Subordo: Cynodontia
Infraordo: Eucynodontia
Cladus: Probainognathia
Cladus: Prozostrodontia
Cladus: Mammaliaformes
Classis: Mammalia
Subclassis: Trechnotheria
Infraclassis: Zatheria
Supercohors: Theria
Cohors: Eutheria
Infraclassis: Placentalia
Superordo: Xenarthra
Ordo: Pilosa
Subordo: Folivora
Familia: Bradypodidae
Genus: Bradypus
Species: Bradypus tridactylus
Name
Bradypus tridactylus Linnaeus, 1758
Type locality: "Americae meridionalis arboribus", Surinam (Thomas, 1911)
Holotype: ZSM 43
Synonyms
Bradypus cuculliger Wagler, 1831
Bradypus dysonii (Gray, 1869)
Bradypus flaccidus (Gray, 1850)
Bradypus gularis Rüppell, 1842
Bradypus smithii (Gray, 1869)
Bradypus flaccions Sanderson, 1949
Acheus ai (Lesson, 1827)
References
Linnaeus, C. 1758. Systema Naturae per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, Tomus I. Editio decima, reformata. Holmiæ: impensis direct. Laurentii Salvii. i–ii, 1–824 pp DOI: 10.5962/bhl.title.542: 34. Reference page.
Bradypus tridactylus in Mammal Species of the World.
Wilson, Don E. & Reeder, DeeAnn M. (Editors) 2005. Mammal Species of the World – A Taxonomic and Geographic Reference. Third edition. ISBN 0-8018-8221-4.
IUCN: Bradypus tridactylus Linnaeus, 1758 (Least Concern)
Bradypus tridactylus Linnaeus, 1758 – Taxon details on Integrated Taxonomic Information System (ITIS).
Vernacular names
български: Трипръст ленивец
brezhoneg: Lezireg tri biz
català: Peresós de coll pàl·lid
Deutsch: Weißkehl-Faultier
English: Pale-throated Three-toed Sloth
español: Bradypus tridactylus, mono perezoso
euskara: Hiru hatzeko nagi
suomi: Kolmivarvaslaiskiainen
français: Paresseux à trois doigts
hrvatski: Troprsti ljenivac
magyar: Háromujjú lajhár
italiano: Bradipo tridattilo
日本語: ノドジロミユビナマケモノ
한국어: 엷은목세발가락나무늘보
Nederlands: Drievingerige luiaard
polski: Leniwiec trójpalczasty
português: Preguiça-de-bentinho, Bicho-preguiça
slovenčina: Leňoch trojprstý
српски / srpski: Тропрсти лењивац
svenska: Tretåig sengångare
Türkçe: Üç parmaklı tembelhayvan
中文: 白喉三趾樹懶
The pale-throated sloth (Bradypus tridactylus), occasionally known as the ai (/ˈɑːi/),[4] is a species of three-toed sloth that inhabits tropical rainforests in northern South America.
It is similar in appearance to, and often confused with, the brown-throated sloth, which has a much wider distribution. Genetic evidence has been interpreted to suggest the two species diverged only around 400,000 years ago, although the most recent evidence indicates the split was closer to 6 million years.[5][6]
Description
Skull
Pale-throated sloths have a rounded head with a blunt nose and small external ears. The limbs are long and weak, with the arms being nearly twice the length of the hindlimbs. The hands and feet each have three digits, armed with long, arched claws, with the middle claw being the largest and most powerful. Males are 45 to 55 centimetres (18 to 22 in) in head-body length, with a short, 4 to 6 centimetres (1.6 to 2.4 in), tail, and weigh from 3.2 to 6 kilograms (7.1 to 13.2 lb). However, the females are noticeably larger, being from 50 to 75 centimetres (20 to 30 in) in length, and weighing 3.8 to 6.5 kilograms (8.4 to 14.3 lb).[7]
The body is covered with coarse guard hairs up to 10 centimetres (3.9 in) long, with a finer undercoat. Green algae live mutualistically between the microscopic scales on the surface of the guard hairs, giving the sloth a somewhat greenish appearance that serves as camouflage. Adults are blackish-grey over most of the body, with darker patches distributed over the backs, shoulders, and hips. Males have a bright yellow or orange patch on the back, divided by a central black stripe. Pale-throated sloths are difficult to distinguish from the closely related brown-throated sloth, but, as their name implies, have a pale yellow patch on the throat.[7]
The eyes are large and forward facing for binocular vision, with round pupils. Unusually, they appear to lack any cone cells in the retina, suggesting that the sloth is unable to see color. Despite its apparently small ears, the pale-throated sloth has excellent hearing; it has also been reported to have a good sense of smell.[7]
Anatomy
Skeleton of pale-throated sloth
The sloth has nine cervical vertebrae, giving it extreme flexibility. As a result, a pale-throated sloth can bend its head backwards and forwards through 270° and rotate it through 330°. It possesses a pair of foramina in the anterodorsal nasopharynx, a feature that distinguishes it from its sister species. The females have two mammae in the chest region, a simple uterus. Males have no discrete prostate gland, no scrotum, and only rudimentary seminal vesicles.[7]
The mouth is lined by a black colored mucosa, although the large and heavy tongue is pink. The palate is wrinkled in texture, and the tongue is lined with numerous grooves, apparently adaptations to the sloth's diet. Like other three-toed sloths, it has just five teeth on each side of the upper jaw, and four on each side of the lower jaw; these are all simple and rounded in shape, with the front teeth in the upper jaw being much smaller than the others. The esophagus is short, but the stomach is large and complex, and there is also a large diverticulum in the cecum.[7]
Distribution and habitat
The pale-throated sloth is found only in the tropical forests of northern South America, including Guyana, Suriname, French Guiana, eastern Venezuela and Brazil north of the Amazon River.[2] There are no recognised subspecies.
Behavior and biology
Pale-throated sloths are solitary,[8] herbivorous animals that spend almost their entire lives in trees. Depending on habitat, population densities of anything from 1.7 to 221 per square kilometre (4.4 to 572.4/sq mi) have been reported.[2] They eat only leaves, twigs, and buds of the trees of Cecropia, Ceiba, Elizabetha, and Hevea.[9] Known predators include jaguars, margays, harpy eagles, and anacondas.[7]
The pale-throated sloth can hang so securely with its hooklike claws that it even falls asleep in this position. It may even stay suspended in the trees for some time after it dies. They have been reported to spend over eighteen hours each day asleep, and move through the tree canopy only very slowly. They periodically descend from the trees to defecate, depositing a pile of small pellets in a hole dug into the ground. Despite their arboreal lifestyle, they are effective swimmers. Their call is a bird-like whistle described as an "ai-ai" sound.[7]
In addition to their mutualism with green algae, pale-throated sloths are also commensal with sloth moths, and with certain species of beetle. These insects live in the sloth's fur, and lay their eggs in its dung, on which their larvae feed.[7]
Reproduction
Mating takes place in the trees, with the pair either face to face, or with the male on the female's back. The female gives birth to a single infant after a gestation period of about six months.[10]
The young are born already fully furred, and with open eyes. The young animal clings to the mother's underside for the first month of life, by which time it has reached a weight of around 300 grams (10 oz). They begin to take solid food at three weeks, and are fully weaned some time after the first month. The young initially have soft greyish-brown fur, which darkens and becomes rougher as they age.[7] They reach sexual maturity at around three years.[10]
References
Gardner, A. (2005). Wilson, D.E.; Reeder, D.M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 100. ISBN 978-0-8018-8221-0. OCLC 62265494.
Chiarello, A.; Moraes-Barros, N. (2014). "Bradypus tridactylus". IUCN Red List of Threatened Species. 2014: e.T3037A47436865. doi:10.2305/IUCN.UK.2014-1.RLTS.T3037A47436865.en. Retrieved 19 November 2021.
Linnæus, Carl (1758). Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I (in Latin) (10th ed.). Holmiæ: Laurentius Salvius. p. 34. Retrieved 23 November 2012.
"ai". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
Barros, M.C.; et al. (2003). "Phylogenetic analysis of 16S mitochondrial DNA data in sloths and anteaters". Genetics and Molecular Biology. 26 (1): 5–11. doi:10.1590/S1415-47572003000100002.
Moraes-Barros, M.C.; et al. (2011). "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.
Hayssen, V. (2009). "Bradypus tridactylus (Pilosa: Bradypodidae)". Mammalian Species. 839: 1–9. doi:10.1644/839.1. S2CID 85870343.
Taube, E.; et al. (1999). "Distribution of two sympatric species of sloths (Choloepus didactylus and Bradypus tridactylus) along the Sinnamary River, French Guiana". Biotropica. 31 (4): 686–691. doi:10.1111/j.1744-7429.1999.tb00418.x. S2CID 54226310.
"Pale-Throated Sloth: The Animal Files". www.theanimalfiles.com. Retrieved 2019-06-12.
Taube, E.; et al. (2001). "Reproductive biology and postnatal development in sloths, Bradypus and Choloepus: review with original data from the field (French Guiana) and from captivity". Mammalian Review. 31 (3–4): 173–188. doi:10.1111/j.1365-2907.2001.00085.x.
BBC Science & Nature. "Wildfacts - Pale throated Three-toed Sloth". Retrieved 2007-01-02.
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