Pygmy three-toed sloth

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Pygmy three-toed sloth
Bradypus pygmaeus.jpg
CITES Appendix II (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Pilosa
Family: Bradypodidae
Genus: Bradypus
Species:
B. pygmaeus
Binomial name
Bradypus pygmaeus
Anderson & Handley, 2001
Pygmy Three-toed Sloth area.png
Range of the pygmy three-toed sloth

The pygmy three-toed sloth (Bradypus pygmaeus), 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 (19 and 21 in), and the body mass ranges from 2.5 to 3.5 kg (5.5 to 7.7 lb).

Contents

This sloth, like other sloths, is arboreal (tree-living) and feeds on leaves. It has a body adapted to hang by its limbs; the large curved claws help the sloth to keep a strong grip on tree branches. It lives high in the canopy but descends once a week to defecate on the forest floor. [3] It is symbiotically associated with green algae, that can provide it with a camouflage. Details of mating behavior and reproduction have not been documented. The pygmy three-toed sloth is found exclusively in the red mangroves of Isla Escudos de Veraguas, restricted to an area of 4.3 square kilometres (1.7 sq mi). A 2012 census of pygmy three-toed sloths estimated the total population at 79. The IUCN lists the pygmy three-toed sloth as critically endangered and they are listed on the world's 100 most threatened species.

Discovery and taxonomy

The pygmy three-toed sloth was first described by Robert P. Anderson of the University of Kansas and Charles O. Handley Jr., of the Smithsonian Institution in 2001. The researchers noted that the three-toed sloths found on Isla Escudo de Veraguas were significantly smaller than those that occur on the nearby outer islands of Bocas del Toro Province. Moreover, they differ from other populations in terms of pelage and cranial characteristics. Hence, they considered the three-toed sloths in Isla Escudo de Veraguas to be an independent species and formally described it from the skin and skull of an adult female. The researchers further pointed out that Isla Escudos de Veraguas is the oldest island and located farthest from the mainland, which began breaking up into small islands due to rises in sea levels 10,000 years ago. They proposed that this species evolved from an isolated population that had originated from the mainland population of brown-throated three-toed sloths; it gradually differentiated enough to become an independent species through insular dwarfism. [4] In another study the following year, the researchers observed that the mean body size of three-toed sloths on an island decreases linearly as the age of the island increases; the area of the island and the distance from the mainland, however, do not appear to significantly affect dwarfing. [5]

The pygmy three-toed sloth is one of the four extant members of the genus Bradypus , and is classified under the family Bradypodidae. [6] According to molecular phylogenetic analysis, Bradypodidae nests with Megalonychidae, Megatheriidae and Nothrotheriidae in the sloth superfamily Megatherioidea. [7] [8] The generic name Bradypus is the combination of two Greek words: brady ("slow") and pous ("foot"). [9] The specific name pygmaeus comes from the Greek pugmaios ("as small as a fist"). [10] 'Monk sloth' and 'dwarf sloth' are two other names for this sloth. [11]

Characteristics

Pygmy three-toed sloth on Isla Escudo de Veraguas Perezoso La Mochila.jpg
Pygmy three-toed sloth on Isla Escudo de Veraguas

The pygmy three-toed sloth is significantly smaller than the other members of its genus, but otherwise resembles the brown-throated sloth. According to Anderson and Handley Jr., the head-and-body length is between 48 and 53 centimetres (19 and 21 in), and the body mass ranges from 2.5 to 3.5 kg (5.5 to 7.7 lb). The brown-throated sloth is nearly 40% heavier and 15% smaller in head-and-body length than the pygmy three-toed sloth. Moreover, the brown-throated sloth is lighter on the crown. The face is buff to tan; a dark band runs across the brow, surrounded by an orange patch. The throat is gray to brown, lighter than the underbelly; the dark brown back is spotted and has a dark stripe along the midline. Facial hair is short, while the long, rough hair on the crown and shoulders forms a hood. The grayish limbs have three claws each. The tail is 4.5 to 6 centimetres (1.8 to 2.4 in) long. [4] [5] [12]

They have a relatively small and slender skull, with a large external auditory meatus, narrow squamosal and mandibular processes, a minuscule stylomastoid foramen, and usually lack foramina for the external carotid artery and anterodorsal (meaning in front and toward the back) nasopharynx. The dental formula of three-toed sloths is: 54–5 [13] Two of the teeth in each jaw are incisor-like, although those in the upper jaw are small or may be absent. Many of the features found in pygmy sloths are thought to be indicative of a relatively rapid evolution of a new species in an isolated, island habitat. [4]

They host algae inside their fur which causes them to have a greenish color. The algae is generally more noticeable on the top of their head and neck, dorsal portions of the forelimbs, and upper backside. [14]

Distribution and status

Pygmy three-toed sloths live on red mangroves. Rhizophora yngtree.jpg
Pygmy three-toed sloths live on red mangroves.

The pygmy three-toed sloth is unique in that it is found exclusively in the red mangroves of Isla Escudo de Veraguas; the island has a small area of approximately 4.3 square kilometres (1.7 sq mi). A 2012 census of pygmy three-toed sloths estimated the total population at 79 – of which 70 occurred on mangroves and 9 in the surroundings. The population density was calculated as 5.8 per hectare (2.3 per acre). The total area occupied by mangroves on the island was estimated to be around 10.67 hectares (0.0412 sq mi). [15] While their population has presumably always been low due to their restricted range, the 2012 census found far lower numbers than had been estimated (less than 500) by the IUCN in 2010. [16]

The IUCN lists the pygmy three-toed sloth as critically endangered; it is also listed in CITES Appendix II. According to the IUCN, conservation efforts are being hampered by conflict between local peoples and the government. [1] Threats to the sloth's survival include timber harvesting and human settlement, that might lead to habitat degradation. [17] After several observations, the corpses of the pygmy three-toed sloth were found to be unharmed physically, suggesting that predation is not a major threat. Instead, disease, habitat loss, or natural causes were larger factors in the species’ death. A study in 2011 showed that there were 79 pygmy sloths in the wild. Studies in 2010 and 2013 suggested a recent population bottleneck and decline in genetic variability. [1]

Ecology and behavior

The pygmy three-toed sloth, like others in its genus, is an arboreal (tree-living) animal. This sloth can spend as many as 15 to 20 hours per day on trees. It moves at an extremely slow speed of 0.24 kilometres per hour (0.15 mph), making it one of the slowest animals. [18] The pygmy three-toed sloth is symbiotically related to green algae; a 2010 study investigated this in detail. Different sloths harbour different types of algae – only Tricophilus species were found on the brown-throated and pygmy three-toed sloths. These algae discolor the fur of the sloth, giving it a greenish hue – this serves as an efficient camouflage. [19] Some of these algae might be transferred to offspring through the mother, others may be picked up from the surroundings over time. [20] The smaller size of pygmy sloths reduces their energy requirements for survival and reproduction, making them an apparent example of insular dwarfism. [5] A BBC documentary, in which English naturalist Chris Packham recognizes the pygmy three-toed sloth as the first in his list of the top ten discoveries in the 2000s, shows a rare clip of a swimming pygmy three-toed sloth. [21]

Like other sloths, the pygmy three-toed sloth feeds on leaves. It feeds on red mangrove leaves, which are relatively poor in nutrients and coarser than the tender leaves of Cecropia species eaten by brown-throated sloths on the mainland. [5] Details of mating behavior and reproduction have not been documented. [11]

See also

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">Pale-throated sloth</span> Species of mammals related to anteaters and armadillos

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

<span class="mw-page-title-main">Maned sloth</span> Species of mammals related to anteaters and armadillos

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.

<span class="mw-page-title-main">Brown-throated sloth</span> Species of New World mammals related to anteaters and armadillos

The brown-throated sloth is a species of three-toed sloth found in the Neotropical realm of Central and South America.

<span class="mw-page-title-main">Hoffmann's two-toed sloth</span> Species of mammals related to anteaters and armadillos

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.

<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.

<span class="mw-page-title-main">Sloth</span> Group of tree dwelling mammals noted for slowness

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.

<span class="mw-page-title-main">Cozumel raccoon</span> Species of critically endangered raccoon

The Cozumel raccoon is a critically endangered species of island raccoon endemic on Cozumel Island off the coast of the Yucatan Peninsula, Mexico. It is sometimes also called the pygmy raccoon, dwarf raccoon, Cozumel Island raccoon, and Cozumel raccoon bear.

<span class="mw-page-title-main">Isla Escudo de Veraguas</span>

Isla Escudo de Veraguas is a small (4.3 km2) isolated Caribbean island of the Republic of Panama. Despite its name, it is not part of the province of Veraguas, but rather Bocas del Toro. Although located only 17 km from the coastline in the Golfo de los Mosquitos and isolated for only about 9000 years, several animals found on the island are distinct from their mainland counterparts, and two mammal species or subspecies are recognized as occurring only on the island: the fruit bat Dermanura watsoni incomitata and the sloth Bradypus pygmaeus. These two taxa and the worm salamander Oedipina maritima are all considered to be critically endangered due to their being unique to the small island. Other mammals found on the island include the bats Glossophaga soricina, Micronycteris megalotis, Carollia brevicauda, Myotis riparius, and Saccopteryx leptura, the spiny rat Hoplomys gymnurus, and the opossum Caluromys derbianus. The island has 26.36 acres (10.67 ha) of mangrove forest and 247 acres (100 ha) of coral reef with 55 coral species. It houses over 11,000 species, such as the pygmy sloth. The island has an average high temperature of 23 degrees Celsius and a low temperature of 12 degrees Celsius.

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.

<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.

References

  1. 1 2 3 Voirin, B.; Smith, D.; Chiarello, A.; Moraes-Barros, N. (2014). "Bradypus pygmaeus". IUCN Red List of Threatened Species . 2014: e.T61925A47444229. doi: 10.2305/IUCN.UK.2014-1.RLTS.T61925A47444229.en . Retrieved 19 November 2021.
  2. ↑ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. ↑ "Amazing Facts about the Three Toed Sloth | OneKindPlanet Education". OneKindPlanet. Retrieved 2019-06-12.
  4. 1 2 3 Anderson, R.P.; Handley Jr., C. O. (2001). "A new species of three-toed sloth (Mammalia: Xenarthra) from Panama, with a review of the genus Bradypus". Proceedings of the Biological Society of Washington . 114 (1): 1–33. Open Access logo PLoS transparent.svg
  5. 1 2 3 4 Anderson, R.P.; Handley Jr., C.O. (2002). "Dwarfism in insular sloths: biogeography, selection, and evolutionary rate". Evolution . 56 (5): 1045–58. doi: 10.1111/j.0014-3820.2002.tb01415.x . PMID   12093018. S2CID   12803566. Open Access logo PLoS transparent.svg
  6. ↑ 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. p. 100. ISBN   978-0-8018-8221-0. OCLC   62265494.
  7. ↑ Delsuc, F.; Kuch, M.; Gibb, G. C.; Karpinski, E.; Hackenberger, D.; Szpak, P.; Martínez, J. G.; Mead, J. I.; McDonald, H. G.; MacPhee, R.D.E.; Billet, G.; Hautier, L.; Poinar, H. N. (2019). "Ancient Mitogenomes Reveal the Evolutionary History and Biogeography of Sloths". Current Biology. 29 (12): 2031–2042.e6. doi: 10.1016/j.cub.2019.05.043 . hdl: 11336/136908 . PMID   31178321.
  8. ↑ Presslee, S.; Slater, G. J.; Pujos, F.; Forasiepi, A. M.; Fischer, R.; Molloy, K.; Mackie, M.; Olsen, J. V.; Kramarz, A.; Taglioretti, M.; Scaglia, F.; Lezcano, M.; Lanata, J. L.; Southon, J.; Feranec, R.; Bloch, J.; Hajduk, A.; Martin, F. M.; Gismondi, R. S.; Reguero, M.; de Muizon, C.; Greenwood, A.; Chait, B. T.; Penkman, K.; Collins, M.; MacPhee, R.D.E. (2019). "Palaeoproteomics resolves sloth relationships" (PDF). Nature Ecology & Evolution. 3 (7): 1121–1130. doi:10.1038/s41559-019-0909-z. PMID   31171860. S2CID   174813630.
  9. ↑ "Bradypus". Merriam-Webster.com Dictionary . Retrieved 28 May 2016.
  10. ↑ Beddard, F.E. (2015). The Cambridge Natural History, Vol X. Mammalia. The Library of Alexandria. ISBN   978-1-5115-9533-9.
  11. 1 2 Hayssen, V. (2008). "Bradypus pygmaeus (Pilosa: Bradypodidae)". Mammalian Species . 812: 1–4. doi:10.1644/812.1. S2CID   84387124. Open Access logo PLoS transparent.svg
  12. ↑ Reid, F.A. (2009). A Field Guide to the Mammals of Central America & Southeast Mexico (2nd ed.). Oxford, UK: Oxford University Press. p. 59. ISBN   978-0-19-534322-9.
  13. ↑ Ungar, P.S. (2010). Mammal Teeth: Origin, Evolution, and Diversity. Baltimore, US: Johns Hopkins University Press. pp. 145–6. ISBN   9780801899515.
  14. ↑ Voirin, Bryson (2015-08-03). "Biology and conservation of the pygmy sloth, Bradypus pygmaeus". Journal of Mammalogy. 96 (4): 703–707. doi:10.1093/jmammal/gyv078. ISSN   0022-2372.
  15. ↑ Kaviar, S.; Shockey, J.; Sundberg, P.; Evans, A.R. (2012). "Observations on the endemic pygmy three-toed sloth, Bradypus pygmaeus of Isla Escudo de Veraguas, Panamá". PLOS ONE . 7 (11): e49854. Bibcode:2012PLoSO...749854K. doi: 10.1371/journal.pone.0049854 . PMC   3504081 . PMID   23185461. Open Access logo PLoS transparent.svg
  16. ↑ "Portraits in Red". IUCN Red List . Archived from the original on 13 December 2007. Retrieved 1 January 2008.
  17. ↑ Voirin, B. (2015). "Biology and conservation of the pygmy sloth, Bradypus pygmaeus". Journal of Mammalogy. 96 (4): 703–7. doi:10.1093/jmammal/gyv078. S2CID   73534122.
  18. ↑ Hearst, M. (2012). Unusual Creatures: A Mostly Accurate Account of some of the Earth's Strangest Animals. San Francisco, US: Chronicle Books LLC. p. 82. ISBN   978-1-4521-1985-4.
  19. ↑ Suutari, M.; Majaneva, M.; Fewer, D.P; Voirin, B.; Aiello, A.; Friedl, T.; Chiarello, A.G; Blomster, J. (2010). "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. doi: 10.1186/1471-2148-10-86 . PMC   2858742 . PMID   20353556.} Open Access logo PLoS transparent.svg
  20. ↑ Feldhamer, G.A.; Drickamer, L.C.; Vessey, S.H.; Merritt, J.F.; Krajewski, C. (2015). Mammalogy: Adaptation, Diversity, Ecology (4th ed.). JHU Press. ISBN   978-1-4214-1588-8.
  21. ↑ Packham, C. (17 March 2011). "Rare swimming pygmy sloth". Decade of Discovery. BBC Two. Event occurs at 51:56. Retrieved 28 May 2016.
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