The maned sloth (Bradypus torquatus), also known as the ai, is a three-toed sloth that lives only in Brazil. It is one of four species of three-toed sloth.
Distribution and habitat
The maned sloth is now found only in the Atlantic coastal rainforest of southeastern Brazil, although it was once also found further north. It has been identified predominantly from evergreen forests, although, being able to eat a wide range of leaves, it can also inhabit semi-deciduous and secondary forest. It is typically found in hot, humid climates without any dry season, and with annual rainfall of at least 120 centimetres (47 in). There are no recognised subspecies.
Anatomy and morphology
Maned sloths have a pale brown to gray pelage. Long outer hair covers a short, dense, black and white underfur. The coarse outer coat is usually inhabited by algae, mites, ticks, beetles, and moths. The maned sloth's small head features fur-covered pinnae and anterior oriented eyes that are usually covered by a mask of black hair. The sides of the maned sloth's face and neck feature long hair covering the short hair of the sloth's snout. Facial vibrissae on the maned sloth are sparse. The maned sloth earns its name from a mane of black hair running down its neck and over its shoulders. The mane is usually larger and darker in males than in females, and in the latter, may be reduced to a pair of long tufts. Other than the mane, the fur is relatively uniform in color, and, in particular, the males lack the patch of bright fur found on the back of other, closely related, sloths.
Adult males have a total head-body length of 55 to 72 centimetres (22 to 28 in), with a tail about 5 centimetres (2.0 in) long and a weight of 4.0 to 7.5 kilograms (8.8 to 16.5 lb). Females are generally larger, measuring 55 to 75 centimetres (22 to 30 in), and weighing 4.5 to 10.1 kilograms (9.9 to 22.3 lb). Like all other sloths, the maned sloth has very little muscle mass in comparison to other mammals its size. This reduced muscle mass allows it to hang from thin branches.
Ecology and behavior
Maned sloths are solitary diurnal animals, spending from 60–80% of their day asleep, with the rest more or less equally divided between feeding and travelling. Sloths sleep in crotches of trees or by dangling from branches by their legs and tucking their head in between their forelegs.
Maned sloths are folivores, and feed exclusively on tree and liana leaves, especially Cecropia. Although individual animals seem to prefer leaves from particular species of tree, the species as a whole is able to adapt to a wide range of tree types. Younger leaves are preferred to older, and tree leaves are preferred to liana leaves. Individual maned sloths have reported to travel over a home range of 0.5 to 6 hectares (1.2 to 14.8 acres), with estimated population densities of 0.1 to 1.25 per hectare (0.040 to 0.506/acre).
Maned sloths rarely descend from the trees because, when on a level surface, they are unable to stand and walk, only being able to drag themselves along with their front legs and claws. They travel to the ground only to defecate or to move between trees when they cannot do so through the branches. The sloth's main defenses are to stay still and to lash out with its formidable claws. It can swim well.
Although some reports indicate that maned sloths are able to breed year round, others have observed that the majority of births occur between February and April. The mother gives birth to a single young, which initially weighs around 300 grams (11 oz) and lacks the distinctive mane found on adults. The young begin to take solid food at two weeks, and are fully weaned by two to four months of age. The young leave the mother at between nine and eleven months of age. Although their lifespan has not been studied in detail, they have been reported to live for at least twelve years.
In 1955, the maned sloth occurred only in Bahia, Espírito Santo and Rio de Janeiro in eastern Brazil, in the Bahia coastal forests. It has declined since then as these forests have dwindled. The major threat to the maned sloth is the loss of its forest habitat as a result of lumber extraction, charcoal production, and clearance for plantations and cattle pastures. Excessive hunting is also a threat.
- ^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. ISBN 978-0-8018-8221-0. OCLC 62265494.
- ^ abChiarello, A. & Moraes-Barros, N. (2014). "Bradypus torquatus". The IUCN Red List of Threatened Species. IUCN. 2014: e.T3036A47436575. doi:10.2305/IUCN.UK.2014-1.RLTS.T3036A47436575.en. Retrieved 4 January 2018.
- ^"ai". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
- ^ abZSL Living Conservation (2010). "Maned three-toed sloth (Bradypus torquatus)". Evolutionary Distinct & Globally Endangered. ZSL Living Conservation. Retrieved 2010-06-07.
- ^World Land Trust (2010). "Maned Three-toed Sloth Bradypus torquatus". World Land Trust. World Land Trust. Retrieved 2010-06-06.
- ^Gardner 2008, p. 158
- ^ abcdHayssen, V. (2009). "Bradypus torquatus (Pilosa: Bradypodidae)". Mammalian Species. 829: 1–5. doi:10.1644/829.1.
- ^Chiarello, A.G. (1998). "Activity budgets and ranging patterns of the Atlantic forest maned sloth". Journal of Zoology. 246 (1): 1–10. doi:10.1111/j.1469-7998.1998.tb00126.x.
- ^Stewart, Melissa (2004). "At the Zoo: Slow and Steady Sloths". Zoogoer. Friends of the National Zoo. Archived from the original on 7 June 2011. Retrieved 2010-06-07.
- ^Adriano, Chiarello (September 1998). "Diet of the Atlantic forest maned sloth Bradypus torquatus". Journal of Zoology. 246 (1): 10. doi:10.1111/j.1469-7998.1998.tb00127.x.
- ^Pinder, L. (1993). "Body measurements, karyotype, and birth frequencies of maned sloth (Bradypus torquatus)". Mammalia. 57 (1): 43–48. doi:10.1515/mamm.19188.8.131.52.
- ^Dias, B.B.; et al. (2009). "First observation on mating and reproductive seasonality in maned sloths Bradypus torquatus (Pilosa: Bradypodidae)". Journal of Ethology. 27 (1): 97–103. doi:10.1007/s10164-008-0089-9.
- ^ abLara-Ruiz, P. & Chiarello, A.G. (2005). "Life-history traits and sexual dimorphism of the Atlantic forest maned sloth Bradypus torquatus (Xenarthra: Bradypodidae)"(PDF). Journal of Zoology. 267 (1): 63–73. doi:10.1017/S0952836905007259.
The genus Bradypus, the sole genus in the family Bradypodidae, includes four species:
1) the Brown-throated Three-toed Sloth (B. variegatus), which is found over much of Central and South America
2) the Pale-throated Three-toed Sloth (B. tridactylus), which is found in northeastern South America
3) the Maned Three-toed Sloth (B. torquatus), which is limited to the remaining fragments of the Atlantic coastal forest in Brazil
4) the Pygmy Three-toed Sloth (B. pygmaeus), described only in 2001, which is found exclusively in Red Mangroves on the several square kilometer Isla Escudo de Veraguas of Bocas del Toro, around 17 km off the Caribbean coast of Panama (Anderson and Handley 2001, 2002; Hayssen 2008)
With the exception of the Pygmy Three-toed Sloth, all three-toed sloths are restricted to New World tropical rainforests. de Moraes-Barros et al. (2011) address the confusion between the Brown-throated and Pale-throated Three-toed Sloths, especially in north-central Brazil (mainly actual Brown-throated specimens misidentified as Pale-throateds).
The two species of two-toed sloths (Hoffmann's Two-toed Sloth, Choloepus hoffmanni, and Southern Two-toed Sloth, C. didactylus) are now placed in the family Megalonychidae (with the extinct giant ground sloths) rather than with the three-toed sloths in the Bradypodidae as they used to be.
Sloth feet have no free toes, but do have two or three long, curved claws that form a hook by which the animals can hang passively from a branch or clasp objects against the palm. Sloths have long limbs, short bodies, and stumpy tails. Their heads can rotate over 90 degrees. Sloths feed mainly on forest canopy leaves, which they digest by bacterial fermentation in a many-chambered stomach. Consistent with their reputation, sloths move slowly—and not much. The single young spends 6 to 9 months clinging to its mother, usually to her chest. Although sloths are silent and inconspicuous, they are preyed on extensively by eagles and, in some places, Jaguars.
The long, coarse hairs of sloths have either deep grooves running the length of each hair (two-toed sloths, Choloepus) or irregular transverse cracks that increase in number and size with age (three-toed sloths, Bradypus). A wide variety of organisms have been reported to occur both in the grooves and cracks of sloth hairs (including cyanobacteria and diatoms) and among their hairs (including moths, beetles, cockroaches, and nematode roundworms). However, the greenish color of the hair, which is most evident in three-toed sloths, is due to green algae, which have generally been identified as Trichophilus welckeri. It is often assumed that the association between three-toed sloths and the algae embedded in their hairs is a mutualistic one, with the algae obtaining shelter in the cracks of the hair while providing green camouflage for the sloth (it has also has been proposed, however, that the relationship may be a commensal one, with the alga offering no benefit to the sloth but simply taking advantage of an available habitat).
Analyses by Suutari et al. (2010) provided support for the hypothesis that there is a specific symbiosis of some sort between sloths and Trichophilus green algae. Suutari et al. identified three different patterns of algae occurrence in the hair of five sloth species: 1) The green alga in the fur of Brown-throated Three-toed Sloths and Pygmy Three-toed Sloths was a unique species and no other green algae were found in their fur. Microscopic features of the algae on the hair were consistent with the genus Trichophilus. 2)Maned Three-toed Sloths were found to host a variety of algae belonging to genera known to be terrestrial,such as Trentepholia and Myrmecia. 3) Hoffmann's Two-toed Sloths and Pale-throated Three-toed Sloths showed both patterns, hosting terrestrial green algae from their surroundings as well as Trichophilus. Molecular phylogenetic analyses of the Trichophilus green algae revealed that those found on Brown-throated Three-toed Sloths, Pygmy Three-toed Slothsand Pale-throated Three-toed Slothsbelong to a separate lineage from those occurring on Hoffmann's Two-toed Sloths. Given that Brown-throated Three-toed Sloths and Hoffmann's Two-toed Sloths co-occur, this finding suggests evolved specialized associations between Trichophilus species and different slothspecies. The three or more Trichophilus green alga species that have been found only in sloth hair are presumably passed directly from mother to offspring.
In addition to primary producers (algae), sloth fur also harbors heterotrophic organisms (ciliates, apicomplexans, and dinoflagellates) as well as decomposers (fungi), suggesting that sloth fur supports a versatile microscopic ecosystem. Several pyralid moths are known to be closely associated with sloths (Waage and Montgomery 1976; Bradley 1982).
(Emmons 1990; Suutari et al. 2010 and references therein)