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Brief Summary

    Three-toed sloth: Brief Summary
    provided by wikipedia

    The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. The four living species of three-toed sloths are the brown-throated sloth, the maned sloth, the pale-throated sloth, and the pygmy three-toed sloth.

    Brief Summary
    provided by EOL authors

    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, Choloepushoffmanni, 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 onBrown-throated Three-toed Sloths, Pygmy Three-toed Sloths andPale-throated Three-toed Sloths belong 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 sloth species. 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)

Comprehensive Description

    Three-toed sloth
    provided by wikipedia

    The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. The four living species of three-toed sloths are the brown-throated sloth, the maned sloth, the pale-throated sloth, and the pygmy three-toed sloth.

    Extant Species

    Image Scientific name Common Name Distribution B. pygmaeus pygmy three-toed sloth Isla Escudos de Veraguas B torquatus Paulo Chaves.jpg B. torquatus maned three-toed sloth Atlantic coastal rainforest of southeastern Brazil Bradypus tridactylus -Parque del Este, Caracas, Venezuela-8.jpg B. tridactylus pale-throated three-toed sloth northern South America, including Guyana, Suriname, French Guiana, western Venezuela and Colombia, and Brazil north of the Amazon River Bradypus.jpg B. variegatus brown-throated three-toed sloth Honduras in the north, through Nicaragua, Costa Rica and Panama into Venezuela, Colombia, Ecuador, Bolivia, Brazil and eastern Peru

    Evolution

    A study of 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.[2]

    Relation to the two-toed sloth

    Although similar to the somewhat larger and generally faster-moving two-toed sloths, 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.[3] It is unclear from which ground-dwelling sloth taxa the three-toed sloths evolved or whether they retain their arboreality from the last common ancestor of sloths; the two-toed sloths appear to nest phylogenetically within one of the divisions of ground-dwelling Caribbean megalonychids,[4] thus probably either descended from them or are part of a clade that invaded the Caribbean multiple times. 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 larger two-toed type will jointly predominate. Famously slow-moving, the sloth travels at an average speed of 0.24 km/h (0.15 mph).[5]

    Characteristics

    Three-toed sloths are about the size of a small dog or a large cat, with the head and body having a combined length around 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. They are frequently referred to as three-toed sloths, but all sloths have three toes; the difference is found in the number of fingers, meaning that they are now more appropriately referred to as three-fingered sloths. This idea was first implemented by Judy Avey-Arroyo, cofounder of the Sloth Sanctuary of Costa Rica, but is now recognized in numerous publications as the correct terminology for these animals.[6]

    Behavior

    Unlike the two-toed sloth, three-toed sloths are agile swimmers. They are still slow in trees.[7] The offspring cling to their mother's bellies for around nine months. They cannot walk on all four limbs, so they must use their front arms and claws to drag themselves across the rainforest floor.

    Three-toed sloths are arboreal (tree-dwelling), with a body adapted to hang by their limbs. They live high in the canopy, but descend once a week to defecate on the forest floor. 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. Large, curved claws help sloths to keep a strong grip on tree branches.[5]

    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.[8]

    Three-toed sloths are predominantly diurnal, although they can be active at any hour of the day, while two-toed sloths are nocturnal.[9]

    Lifecycle

    Members of this genus tend to live around 25 to 30 years, reaching sexual maturation at three to five years of age.

    Three-toed sloths do not have a mating season and breed year round. Females give birth to a single young after a gestation period around six months. 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.[8]

    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.[10] 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.[11]

    The home ranges used by wild brown-throated three-toed sloths in Costa Rica include cacao, pasture, riparian forests, and living fence-rows. 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. The home range for mothers are larger than those of young. After separation, only the mothers use the cacao agro forest, but both use riparian forest. Different types of trees are used by both mother and young, which indicates that this agricultural matrix provides an important habitat type for these animals.[12]

    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, 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.[13]

    Three-toed sloths are unusual amongst the mammals in possessing as many as nine cervical vertebrae, which may be due to mutations in the homeotic genes.[14] All other mammals have seven cervical vertebrae,[15] other than the two-toed sloth and the manatee, which have only six.

    References

    1. ^ Gardner, A.L. (2005). "Order Pilosa". In Wilson, D.E.; Reeder, D.M. 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..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
    2. ^ 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.
    3. ^ 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. doi:10.1073/pnas.93.1.181. PMC 40202. PMID 8552600. Retrieved 2009-12-28.
    4. ^ 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. Biogeography of the West Indies: Patterns and Perspectives. CRC Press. pp. 201–235. ISBN 978-0-8493-2001-9.
    5. ^ a b "Speed of Animals". infoplease.com.
    6. ^ 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.
    7. ^ Three-toed Sloth, National Geographic.
    8. ^ 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.
    9. ^ 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.
    10. ^ 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.
    11. ^ Pauli, J.N. & Peery, M.Z. (2012). "Unexpected strong polygyny in the brown-throated three-toed sloth". PLOS ONE. 7 (12): e51389. doi:10.1371/journal.pone.0051389. PMC 3526605. PMID 23284687.
    12. ^ 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 Biologia Tropical. 59 (4): 1743–1755.
    13. ^ Ungar, P.S. (2010). Mammal Teeth: Origin, Evolution, and Diversity. Baltimore, US: Johns Hopkins University Press. pp. 145–6. ISBN 9780801899515.
    14. ^ "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.
    15. ^ 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. 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.