Brown-throated sloth

Brown-throated sloth
Conservation status
	; Least Concern (IUCN 3.1)
	CITES Appendix II (CITES)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Pilosa
Family:	Bradypodidae
Genus:	Bradypus
Species:	B. variegatus
Binomial name
	Bradypus variegatus; Schinz, 1825
Subspecies
	7, see text
	Brown-throated sloth range

Last updated May 14, 2024

The brown-throated sloth (Bradypus variegatus) is a species of three-toed sloth found in the Neotropical realm of Central and South America.^[4]

Description

The brown-throated sloth is of similar size and build to most other species of three-toed sloths, with both males and females being 42 to 80 cm (17 to 31 in) in total body length. The tail is relatively short, only 2.5 to 9 cm (1.0 to 3.5 in) long. Adults weigh from 2.25 to 6.3 kg (5.0 to 13.9 lb), with no significant size difference between males and females. Each foot has three fingers, ending in long, curved claws, which are 7 to 8 cm (2.8 to 3.1 in) long on the fore feet, and 5 to 5.5 cm (2.0 to 2.2 in) on the hind feet.^[6]

The head is rounded, with a blunt nose and inconspicuous ears. As with other sloths, the brown-throated sloth has no incisor or canine teeth, and the cheek teeth are simple and peg-like. They have no gall bladder, cecum, or appendix.^[6]

The brown-throated sloth has grayish-brown to beige-color fur over the body, with darker brown fur on the throat, the sides of the face, and the forehead. The face is generally paler in color, with a stripe of very dark fur running beneath the eyes.^[6]

The guard hairs are very coarse and stiff, and overlie a much softer layer of dense under-fur. The hairs are unusual in lacking a central medulla, and have numerous microscopic cracks across their surfaces. These cracks are host to a number of commensal species of algae, including Rufusia pillicola , Dictyococcus bradypodis , and Chlorococcum choloepodis . The algae are generally absent in the hair of young sloths, and may also be absent in particularly old individuals, where the outer cuticle of the hair has been lost.^[6] Sloth hair also harbours a rich fungal flora.^[7] Certain strains of fungi that grow on brown-throated sloth fur have been shown to possess anti-parasitic, anti-cancer, and anti-bacterial qualities.^[8]

Over parts of its range, the brown-throated sloth overlaps the range of Hoffmann's two-toed sloth. Where this overlap occurs, the three-toed sloth tends to be smaller and more numerous than its relative, being more active in moving through the forest and maintaining more diurnal activity.^[9]

Male showing black patch between shoulders
female

Distribution and habitat

The brown-throated sloth is the most widespread and common of the three-toed sloths. It is found from Honduras in the north, through Nicaragua, Costa Rica and Panama into Venezuela, Colombia, Ecuador, Bolivia, Brazil and eastern Peru. It is probably not found immediately north of the Amazon Rainforest or east of the Rio Negro, although its similarity to the pale-throated sloth found in these regions has led to some confusion in the past.^[6]

It is found in many different kinds of environments, including evergreen and dry forests and in highly perturbed natural areas. It is generally found from sea level to 1,200 m (3,900 ft), although some individuals have been reported from much higher elevations.

Behaviour and diet

Brown-throated sloths sleep 15 to 18 hours every day and are active for only brief periods of time, which may be during either the day or night. Although they can walk along the ground, and even swim, they spend most of their lives in the high branches of trees, descending once every eight days or so to defecate in the soil. The brown-throated sloths are cathemeral, with no preference for sleeping at day or night.^[10] Large, curved claws and muscles specifically adapted for strength and stamina help them to keep a strong grip on tree branches.^[11] They are able to withstand hanging inverted for extended periods of time due to fibrinous adhesions which attach their organs (such as their liver and stomach) to their lower ribs.^[12] Given that feces and urine can account for up to a third of their body weight, this adaptation prevents these organs from pressing on the lungs when hanging upside down, making breathing easier.^[12] Adult animals are solitary, except when raising young, and males have been observed to fight one another using their fore claws.^[6]

Brown-throated sloths inhabit the high canopy of the forest, where they eat young leaves from a wide range of different trees (primarily in the genus Cecropia ), as well as flowers and fruits.^[13] They do not travel far, with home ranges of only around 0.5 to 9 ha (1.2 to 22.2 acres), depending on the local environment. Within a typical, 5-hectare (12-acre) range, a brown-throated sloth will visit around 40 trees, and may specialise on one particular species, even spending up to 20% of its time in a single specific tree. Thus, although the species are generalists, individual sloths may feed on a relatively narrow range of leaf types.^[6] Although they get most of their fluids from the leaves that they eat, brown-throated sloths have been observed drinking directly from rivers.^[14]

Sloths descend about once every eight days to defecate on the ground. The reason and mechanism behind this behavior have long been debated among scientists. There are at least five hypotheses: 1) fertilize trees when feces are deposited at the base of the tree;^[15] 2) cover feces and avoid predation;^[16]^[17]^[18] 3) chemical communication between individuals;^[19] 4) pick up trace nutrients in their claws, that are then ingested;^[20] and 5) favor a mutualistic relationship with populations of fur moths.^[20]^[18] More recently, a new hypothesis has emerged, which presents evidence against the previous ones and proposes that all current sloths are descendants from species that defecated on the ground, and there simply has not been enough selective pressure to abandon this behavior, since cases of predation during defecation are actually very rare.^[21]

In addition to the algae in their fur, brown-throated sloths also live commensally with a species of moth, Cryptoses choloepi , which lives in their fur, and lays its eggs in the dung.^[22] Jaguars and harpy eagles are among the few natural predators of the brown-throated sloth. The yellow-headed caracara has been observed to forage for small invertebrates in the fur of the sloths, apparently without the sloth being disturbed by the attention.^[23]

The female of the species is known to emit a loud, shrill scream during the mating season to attract males. Its cry sounds like "ay ay", much like that of a woman screaming. The male can be identified by a black stripe surrounded by orange fur on its back between the shoulders.

Reproduction

Brown-throated sloths have a polygynous mating system.^[24] Studies of the brown-throated sloth indicate that mating is most common between January and March in at least the northern parts of its range, but this may vary elsewhere. Gestation lasts at least seven months, and the single young is born fully furred and clawed. Young sloths cling to the mother's underside for five months or more, even though they are fully weaned after just four to five weeks.^[25]

The mammary glands of the females do not store significant quantities of milk as most other mammals do, since the infant sloth remains attached to the nipple at all times, and consumes the milk as soon as it is generated.^[26] The young begin to take solid food as early as four days after birth, initially licking particles of food from their mother's mouths. This process apparently allows them to quickly identify edible leaves, and young sloths typically have the same preferences for leaf types as their mothers.^[6]

In the wild, the lifespan of adult brown-throated three-toed sloths is typically between 30 and 40 years.^{[ citation needed ]}

Taxonomy

The brown-throated sloth was first described by Heinrich Rudolf Schinz in 1825 from a South American specimen.^[27] The type locality was later specified as "probably Bahia (Brazil)" by Robert Mertens in 1925.^[28]

The seven recognized subspecies of the brown-throated sloth, although these are not all readily distinguishable, are:^[29]

B. v. boliviensis Gray, 1871
B. v. brasiliensis Blainville, 1840
B. v. ephippiger Philippi, 1870
B. v. gorgon Thomas, 1926
B. v. infuscatus Wagler, 1831
B. v. trivittatus Cornalia, 1849
B. v. variegatus Schinz, 1825

The closest living relative of the species is the pale-throated sloth, which has a very similar appearance, except for the color of the fur around the throat. The two species are estimated to have diverged just 400,000 years ago, whereas their ancestors diverged from the maned sloth over 7 million years ago.^[30]

Related Research Articles

<span class="mw-page-title-main">Xenarthra</span> Superorder of mammals including anteaters, sloths, and armadillos

Xenarthra is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Extinct xenarthrans include the glyptodonts, pampatheres and ground sloths. Xenarthrans originated in South America during the late Paleocene about 60 million years ago. They evolved and diversified extensively in South America during the continent's long period of isolation in the early to mid Cenozoic Era. They spread to the Antilles by the early Miocene and, starting about 3 million years ago, spread to Central and North America as part of the Great American Interchange. Nearly all of the formerly abundant megafaunal xenarthrans became extinct at the end of the Pleistocene.

<span class="mw-page-title-main">Giant anteater</span> Species of mammal

The giant anteater is an insectivorous mammal native to Central and South America. It is one of four living species of anteaters, of which it is the largest member. The only extant member of the genus Myrmecophaga, it is classified with sloths in the order Pilosa. This species is mostly terrestrial, in contrast to other living anteaters and sloths, which are arboreal or semiarboreal. The giant anteater is 182 to 217 cm in length, with weights of 33 to 50 kg for males and 27 to 47 kg for females. It is recognizable by its elongated snout, bushy tail, long fore claws, and distinctively colored pelage.

The pale-throated sloth, occasionally known as the ai, is a species of three-toed sloth that inhabits tropical rainforests in northern South America.

The maned sloth is a three-toed sloth that is native to South America. It is one of four species of three-toed sloths belonging to the suborder Xenarthra and are placental mammals. They are endemic to the Atlantic coastal rainforest of southeastern and northeastern Brazil, located in the states of Espírito Santo, Rio de Janeiro and Bahia. Each of the individuals within the species are genetically distinct with different genetic makeup.The maned sloth is listen under Vulnerable (VU) according to the IUCN Red List and have a decreasing population trend.

The silky anteater, also known as the pygmy anteater, has traditionally been considered a single species of anteater, Cyclopes didactylus, in the genus Cyclopes, the only living genus in the family Cyclopedidae. Found in southern Mexico, and Central and South America, it is the smallest of all known anteaters. It has nocturnal habits and appears to be completely arboreal; its hind feet are highly modified for climbing.

The Hoffmann's two-toed sloth, also known as the northern two-toed sloth, is a species of sloth from Central and South America. It is a solitary, largely nocturnal and arboreal animal, found in mature and secondary rainforests and deciduous forests. The common name commemorates the German naturalist Karl Hoffmann.

Linnaeus's two-toed sloth, also known as the southern two-toed sloth, unau, or Linne's two-toed sloth is a species of sloth from South America, found in Venezuela, Suriname, Guyana, French Guiana, Colombia, Ecuador, Peru, and Brazil north of the Amazon River. There is now evidence suggesting the species' range expands into Bolivia. It's the largest extant sloth species.

<span class="mw-page-title-main">Two-toed sloth</span> Genus of sloth

Choloepus is a genus of xenarthran mammals of Central and South America within the monotypic family Choloepodidae, consisting of two-toed sloths, sometimes also called two-fingered sloths. The two species of Choloepus, Linnaeus's two-toed sloth and Hoffmann's two-toed sloth, were formerly believed on the basis of morphological studies to be the only surviving members of the sloth family Megalonychidae, but have now been shown by molecular results to be closest to extinct ground sloths of the family Mylodontidae.

<span class="mw-page-title-main">Three-toed sloth</span> Genus of mammals

The three-toed or three-fingered sloths are arboreal neotropical mammals. They are the only members of the genus Bradypus 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.

Sloths are a Neotropical group of xenarthran mammals constituting the suborder Folivora, including the extant arboreal tree sloths and extinct terrestrial ground sloths. Noted for their slowness of movement, tree sloths spend most of their lives hanging upside down in the trees of the tropical rainforests of South America and Central America. Sloths are considered to be most closely related to anteaters, together making up the xenarthran order Pilosa.

The pygmy three-toed sloth, also known as the monk sloth or dwarf sloth, is a species of sloth in the family Bradypodidae. The species is endemic to Isla Escudo de Veraguas, a small island off the Caribbean coast of Panama. The species was first described by Robert P. Anderson of the University of Kansas and Charles O. Handley Jr., of the Smithsonian Institution in 2001. The pygmy three-toed sloth is significantly smaller than the other three members of its genus, but otherwise resembles the brown-throated three-toed sloth. According to Anderson and Handley Jr., the head-and-body length is between 48 and 53 centimetres, and the body mass ranges from 2.5 to 3.5 kg.

Acratocnus is an extinct genus of ground sloths that were found on Cuba, Hispaniola, and Puerto Rico.

The mammalian order Pilosa, which includes the sloths and anteaters, includes various species from the Caribbean region. Many species of sloths are known from the Greater Antilles, all of which became extinct over the last millennia, but some sloths and anteaters survive on islands closer to the mainland.

A sloth moth is a coprophagous moth which has evolved to exclusively inhabit the fur of sloths and to use sloth dung as a substrate for the early stages of reproduction. Sloth moths include Bradypodicola hahneli, Cryptoses choloepi, Cryptoses waagei, Cryptoses rufipictus, and Bradypophila garbei.

Cryptoses choloepi is a sloth moth in the snout moth family that as an adult lives exclusively in the fur of sloths, mammals found in South and Central America.

<span class="mw-page-title-main">Arthropods associated with sloths</span>

A large number of arthropods are associated with sloths. These include biting and blood-sucking flies such as mosquitoes and sandflies, triatomine bugs, lice, ticks and mites. The sloth’s fur forms a micro-ecozone inhabited by green algae and hundreds of insects. Sloths have a highly specific community of commensal beetles, mites and moths.

Rebecca Cliffe is a British zoologist, award winning conservationist, and one of the leading experts on sloth biology and ecology. She is the Founder and Executive Director of The Sloth Conservation Foundation and author of the book Sloths: Life in the Slow Lane.

TheSloth Conservation Foundation (SloCo) is a non-profit organisation based in Costa Rica that is dedicated to the protection of sloths living in wild and human-modified habitats through research, education and community-based conservation. SloCo was founded in 2017 by sloth researcher Dr. Rebecca Cliffe.

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.
↑ Moraes-Barros, N.; Chiarello, A.; Plese, T. (2014). "Bradypus variegatus". IUCN Red List of Threatened Species . 2014: e.T3038A47437046. doi: 10.2305/IUCN.UK.2014-1.RLTS.T3038A47437046.en . Retrieved 19 November 2021.
↑ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
↑ Gardner, A. L. (2007). "Bradypus variegatus Schinz, 1825". In Gardner, A. L. (ed.). Mammals of South America. Vol. 1: Marsupials, Xenarthrans, Shrews, and Bats. Chicago: University of Chicago Press. pp. 161–164. ISBN 978-0-226-28240-4.
↑ Emmons, Louise H.; Feer, François (February 1997). Neotropical rainforest mammals. A field guide (2nd ed.). Chicago: University of Chicago Press. p. 43. ISBN 978-0-226-20721-6. OCLC 44179508.
1 2 3 4 5 6 7 8 Hayssen, V. (2010). "Bradypus variegatus (Pilosa: Bradypodidae)". Mammalian Species (42): 19–32. doi: 10.1644/850.1 .
↑ Higginbotham S, Wong WR, Linington RG, Spadafora C, Iturrado L, Arnold AE (2014). "Sloth hair as a novel source of fungi with potent anti-parasitic, anti-cancer and anti-bacterial bioactivity". PLOS ONE. 9 (1): e84549. Bibcode:2014PLoSO...984549H. doi: 10.1371/journal.pone.0084549 . PMC 3893167 . PMID 24454729.
↑ Higginbotham, Sarah; Wong, Weng Ruh; Linington, Roger G.; Spadafora, Carmenza; Iturrado, Liliana; Arnold, A. Elizabeth (2014-01-15). "Sloth Hair as a Novel Source of Fungi with Potent Anti-Parasitic, Anti-Cancer and Anti-Bacterial Bioactivity". PLOS ONE. 9 (1): e84549. Bibcode:2014PLoSO...984549H. doi: 10.1371/journal.pone.0084549 . ISSN 1932-6203. PMC 3893167 . PMID 24454729.
↑ Dickman, Chris (1993). Macdonald, David (ed.). The Encyclopedia of Mammals. p. 777.
↑ Castro-Sa, M. J., Dias-Silva, R. H. P., & Barnett, A. A. (2021). Where to go when all options are terrible: ranging behavior of brown-throated three-toed sloths (Bradypus variegatus) in central Amazonian flooded igapó forests. Canadian Journal of Zoology, 99(9), 823–831. https://doi.org/10.1139/cjz-2020-0176
↑ 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.
1 2 Cliffe, Rebecca N.; Avey-Arroyo, Judy A.; Arroyo, Francisco J.; Holton, Mark D.; Wilson, Rory 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.
↑ "Bradypus variegatus (Brown-throated three-toed sloth)". Animal Diversity Web .
↑ 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.
↑ Montgomery, G. G., & Sunquist, M. E. (1975). Impact of Sloths on Neotropical Forest Energy Flow and Nutrient Cycling. Ecological Studies, 69–98. DOI:10.1007/978-3-642-88533-4_7
↑ Bailey, T. N. (1974). Social organization in a bobcat population. The Journal of Wildlife Management, 38(3),435-446.
↑ Liberg, O. (1980). Spacing patterns in a population of rural free roaming domestic cats. Oikos, 32(3),336-349.
1 2 Pauli, J. N., Mendoza, J. E., Steffan, S. A., Carey, C. C., Weimer, P. J., & Peery, M. Z. (2014). 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
↑ Chiarello, A. G. (2008). Sloth ecology: an overview of field studies. The biology of the Xenarthra, 269-280.
1 2 Voirin, B., Kays, R., Wikelski, M., & Lowman, M. (2013). Why Do Sloths Poop on the Ground? In M. Lowman, S. Devy, & T. Ganesh (eds). Treetops at Risk(pp. 195-199). Springer, New York, NY.
↑ Monge Nájera, J. (2021). Why sloths defecate on the ground: rejection of the mutualistic model. UNED Research Journal, 13(1), 4-4.
↑ Waage, J.K. & Montgomery, G.G. (1976). "Cryptoses choloepi: a coprophagous moth that lives on a sloth". Science. 193 (4248): 157–158. Bibcode:1976Sci...193..157W. doi:10.1126/science.193.4248.157. PMID 17759254. S2CID 32766454.
↑ Krakauer, A.H. & Krakauer, T.H. (1999). "Foraging of yellow-headed caracaras in the fur of a three-toed sloth" (PDF). Journal of Raptor Research. 33 (3): 270.
↑ Pauli, Jonathan N.; Peery, M. Zachariah (2012-12-19). "Unexpected Strong Polygyny in the Brown-Throated Three-Toed Sloth". PLOS ONE. 7 (12): e51389. Bibcode:2012PLoSO...751389P. doi: 10.1371/journal.pone.0051389 . ISSN 1932-6203. PMC 3526605 . PMID 23284687.
↑ 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". Mammal Review. 31 (3–4): 173–188. doi:10.1111/j.1365-2907.2001.00085.x.
↑ Mirsky, Steve (2009). "The Bradypus Bunch". Scientific American. 300 (5): 34. Bibcode:2009SciAm.300e..34M. doi:10.1038/scientificamerican0509-34 (inactive 2024-03-08).{{cite journal}}: CS1 maint: DOI inactive as of March 2024 (link)
↑ Schinz, H. R. (1825). Das Thierreich Eingetheilt nach dem Bau der Thiere als Grundlage ihrer Naturgeschichte und der Vergleichenden Anatomie [The Animal Kingdom Divided according to the Building of the Animals as the Basis of their Natural History and the Comparative Anatomy] (in German). Stuttgart and Tubingen: J. G. Cotta. p. 510.
↑ Mertens, R. (1925). "Verzeichnis der saugetier-typen des Senckenbergischen Museums" [Directory of the mammal types of the Senckenberg Museum]. Senckenbergiana (in German). 7: 18–37.
↑ Anderson, R.P. & Handley, C.O. Jr. (2001). "A new species of three-toed sloth (Mammalia: Xenarthra) from Panamá, with a review of the genus Bradypus". Proceedings of the Biological Society of Washington. 114 (1): 1–33. PDF copy Archived 2010-06-13 at the Wayback Machine
↑ Barros, M.C.; et al. (2003). "Phylogenetic analysis of 16S mitochondrial DNA data in sloths and anteaters" (PDF). Genetics and Molecular Biology. 26 (1): 5–11. doi: 10.1590/S1415-47572003000100002 .