Overview

Brief Summary

Biology

Very little is known about the biology of the pygmy three-toed sloth, although much can be inferred from what is known about three-toed sloths generally. Three-toed sloths are arboreal folivores that eat the leaves of a variety of trees. This is an energy-poor diet, and these animals have a very low metabolic rate (3). Their main defences are camouflage, stealth and stillness, whereby they avoid predation largely by avoiding detection (3) (5). However, should they be attacked, sloths also have a remarkable capacity to survive due to their tough hides, tenacious grips and extraordinary ability to heal from grievous wounds (5).
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Description

With only a small population confined to a single tiny island off the coast of Panama, the pygmy three-toed sloth is the most endangered of all Xenarthra. As its name suggests, this recently discovered species is a dwarf compared with its mainland relatives (4). In addition to its small size, the pygmy three-toed sloth is characterised by usually blotchy, pale grey-brown fur and a tan-coloured face with a distinctive dark band across the forehead, from which long, shaggy hair hangs over the face, giving a hooded appearance. Sloths have an unusual means of camouflage to avoid predation; their outer fur is often coated in algae, giving the pelage a greenish tint that helps hide them in their forest habitat. Three-toed sloths (Bradypus) can be distinguished from their distant relatives, the two-toed sloths (Choloepus), by the three digits on their forelimbs, blunter muzzle, and simpler, peg-like teeth (3).
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Distribution

Bradypus pygmaeus, commonly called monk, dwarf, or pygmy three-toed sloth, is found only on the Isla Escudo de Veraguas of Bocas del Toro, which is located off the coast of Panama. This island is small, only about 5 square kilometers in area.

Biogeographic Regions: neotropical (Native )

Other Geographic Terms: island endemic

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Range Description

Bradypus pygmaeus is known only from Isla Escudo de Veraguas, in the islands of Bocas del Toro, Panama. Sloths on the younger islands of the Bocas del Toro archipelago are conspecific with Bradypus variegatus. Isla Escudo de Veraguas has an area of approximately 4.3 km² and is about 17.6 km from the mainland of Panama.
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Range

Known only from Isla Escudo de Veraguas in the archipelago of Bocas del Toro, Panama (1) (3).
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Physical Description

Morphology

Bradypus pygmaeus is similar to Bradypus variegatus but smaller. Pygmy three-toed sloths have buff-colored faces with dark circles that surround the eye and go outwards to their temples. Clay-orange fur covers the face, starting underneath the dark eye circles. The hair on the head and shoulders is long and bushy, distinctive against the shorter facial hair and making it look as if these sloths have a hood. The throat is brown-gray and the dorsum is speckled and has a dark mid-sagittal stripe. Males differ in that they have a dorsal ginger speculum with fuzzy hair following the margin. Pygmy three-toed sloths have in total 18 teeth, 10 from the upper jaw which consists of 2 anterior chisel-shaped teeth and 8 molariform teeth. On the bottom jaw there are 8 teeth; 2 anterior chisel-shaped, and 6 molariform teeth. The skull is small in comparison to other closely related species, lacks foramina in the anterodorsal nasopharynx, and doesn't have pterygoid sinuses that are inflated. The zygomatic arch is incomplete with slim roots, and the process of the jugal descends long and thin. Bradypus pygmaeus also have large external auditory meatus. Like other sloths, body temperature regulation is likely to be imperfect, making them heterothermic.

Range mass: 2.5 to 3.5 kg.

Average mass: 2.9 kg.

Range length: 485 to 530 mm.

Average length: 505.4 mm.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes colored or patterned differently

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Type Information

Type for Bradypus pygmaeus Anderson & Handley, 2001
Catalog Number: USNM 579179
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Female; Adult
Preparation: Skin; Skull
Collector(s): C. Handley & E. Nelson
Year Collected: 1991
Locality: Isla Escudo de Veraguas, N quarter W point, Bocas Del Toro, Panama, North America
Microhabitat: Ecological remarks by collector(s): yes
  • Type: Anderson, R. P. & Handley, C. O. 2001 Apr 19. Proceedings of the Biological Society of Washington. 114 (1): 17.
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Ecology

Habitat

Bocas del Toro-San Bastimentos Island-San Blas Mangroves Habitat

This taxon is found in the Bocas del Toro-San Bastimentos Island-San Blas mangroves ecoregion, but not necessarily exclusive to this region. The Bocas del Toro-San Bastimentos Island-San Blas mangroves is one of the ecoregions of Panama, situated on the Caribbean coast of northern Panama. Precipitation in this region, entirely in the form of rainfall, amounts to approximately 6000 mm per annum. This ecoregion is largely comprised of mangrove swamps and contains an extensive coral reef system that protects the mangroves by moderating ocean wave action; in turn the mangroves trap sediment and promote water clarity than enhance coral reef development. Extensive submerged areas of this ecoregion are considered seagrass meadows, a highly biodiverse marine ecosystem that has high primary productivity as well as considerable species richness In the shallower waters are found manatee along with numerous corals, sponges, pipefishes and baracuda. The deeper coastal waters are habitat for dolphins, most notably at Dolphin Bay, somewhat south of Bastimentos Island.

The dominant shoreline ecoregion feature is the presence of Red Mangrove trees, whose submerged roots stabilize the shoreline. The near coastal zone and low elevation upland areas of this ecorefion also support a host of other flora, as well as birds, mammals, amphibians and arthropods.

Birdlife at the coastal upland and rich coastal riparian zone and other near shore upland habitats is quite diverse. A notable terrestrial bird endemic to the Bocas del Toro region is the Brown Parakeet. Another notable bird found in this ecoregion is the Pale-billed woodpecker, Campephilus guatemalensis, a large bird, who is found at the southern limit of his range here. The White-fronted nunbird, Monasa morphoeus, is a near passerine species found at the moist lowland forest edge, including secondary growth. Another bird found here that is tolerant of degraded forest is the Crimson-fronted parakeet, Aratinga finschi. A specialist bird to the mangroves and also dense somewhat upland areas of Bocas is the Rufous-necked wood-rail, Aramides axillaris. The Bare-necked umbrella bird is normally found at the higher elevation margin of the Bocas area, but can often be found in the near coastal fringe in non-breeding season.

Mammalian species include the Collared-peccary, who may be found in mainland Bocas del Toro lowland moist forest or grasslands. Also found here is the critically endangered Pygmy three-toed sloth, Bradypus pygmaeus, whose extant population of no more than a few hundred animals is restricted to the tiny (3.4 km2) island of Isla Escudo de Veraguas. There are also Central American red brocket, Mazama temama, a species of forest deer widespead in Mesoamerica.

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Pygmy three-toed sloths have been found living only in coastal, red mangroves at sea level.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: rainforest

Aquatic Biomes: coastal

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Habitat and Ecology

Habitat and Ecology
This smallest of all sloths is found both in mangrove patches and on the interior of Isla Escudo. Although previously thought to exclusively inhabit the red mangroves of the island, recent tracking studies have found the sloths on the interior of the island, in dense tropical rainforest. Because of the difficulty of censusing cryptic canopy mammals, their density and abundance in the thicker forests is unknown. Nothing is known about their reproduction, lifespan, home range, or diet, although it is suspected that it primarily, if not exclusively, feeds on mangrove leaves. Its population is likely larger than previously estimated, but is still limited due to its restricted habitat range.

Systems
  • Terrestrial
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Known exclusively in red mangrove forests surrounding the island at near sea level (1) (3).
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Trophic Strategy

Pygmy three-toed sloths are arboreal folivores. They eat leaves from many different kinds of trees and have low metabolic rates.

Plant Foods: leaves

Primary Diet: herbivore (Folivore )

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Associations

Because pygmy three-toed sloths are a recently described species, little is known about their ecosystem roles. They are hosts to various parasites, may influence vegetation through their browsing, and act as prey for larger, arboreal predators.

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Predators of pygmy three-toed sloths have not been reported. However, like other sloths, they are very slow-moving animals with long, hair that often grows algae, allowing them to blend in well in their leafy habitats. Other sloth species are preyed on by harpy eagles (Harpia harpyja), jaguars (Panthera onca), jaguarundis (Puma yagouaroundi) and ocelots (Leopardus pardalis).

Anti-predator Adaptations: cryptic

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Life History and Behavior

Behavior

There is little information on communication in Bradypus pygmaeus. Like other sloths, pygmy three-toed sloths are likely to have relatively poor eyesight. They may use vocalizations and are likely to use chemical cues in communication.

Perception Channels: visual ; tactile ; acoustic ; chemical

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Life Expectancy

Little information is known at this time about the lifespan or longevity for Bradypus pygmaeus. Other species of sloths have been known to live 30 to 40 years in captivity.

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Reproduction

There is little information on the Bradypus pygmaeus mating system. However, in other Bradypus species, there is evidence that males compete for access to mating opportunities with receptive females.

Reproduction in Bradypus pygmaeus has not been researched enough to report details. Bradypus torquatus has been studied more extensively. They copulate towards the end of the dry season and early wet season, which occurs from August through October, which results in gestation and lactation occurring during times of plenty of food. Births occur from February to April, marking the end to the wet season and start of the dry season. One infant is born after a gestation period of 6 months. The interbirth interval is 1 year for maned sloths.

Breeding interval: A close relative, Bradypus torquatus, breeds once yearly, but the breeding interval for B. pygmaeus is not known.

Average number of offspring: 1.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Female pygmy three-toed sloths invest heavily in young through gestation and lactation, as do females in other sloth species. Details of parental care are not reported for pygmy three-toed sloths, but related species care for their young for up to 6 months.

Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)

  • Bezerra, B. 2008. Observation of Brown-Throated Three Toed Sloths, Mating Behavior and Simultaneous Nurturing of Two Young. Journal of Ethology, 26/1: "175-178".
  • Dias, B. 2009. First Observation on Mating and Reproductive Seasonality in Manned Sloths Bradypus torquatus ( Pilosa: Bradypodidae). Journal of Ethology, 27/1: "97-103".
  • Hayssen, V. 2008. Bradypus pygmaeus (Pilosa:Bradypodidae). Mammalian Species, 812: "1-4". Accessed July 26, 2009 at http://www.bioone.org/doi/pdf/10.1644/812.1.
  • Lynch, W. 2006. Slowpokes. Wildlife Conservation, 109/1: "44-49".
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Conservation

Conservation Status

Because of their extremely restricted range, habitat degradation in that area, increasing tourism, and illegal hunting, Bradypus pygmaeus has been listed as Critically Endangered by the IUCN.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: critically endangered

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IUCN Red List Assessment


Red List Category
CR
Critically Endangered

Red List Criteria
B1ab(ii,iii)+2ab(ii,iii)

Version
3.1

Year Assessed
2014

Assessor/s
Voirin, B., Smith, D., Chiarello, A. & Moraes-Barros, N.

Reviewer/s
Abba, A.M. & Superina, M.

Contributor/s
Anderson, R.P.

Justification
Bradypus pygmaeus is listed as Critically Endangered as this species has a very restricted range, being found only on one very small island less than 5 km² in size, and there is likely a continuing decline in the quality of habitat and area of occupancy due to habitat degradation.

History
  • 2013
    Critically Endangered
  • 2006
    Critically Endangered
    (IUCN 2006)
  • 2006
    Critically Endangered
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Status

Classified as Critically Endangered (CR) on the IUCN Red List 2006 (1).
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Population

Population
There is no accurate information available on the total population size of B. pygmaeus. Previous censuses only searched for sloths in mangroves, which comprise less than 3% of the island. Bradypus pygmaeus has been observed in the interior forests of the island; however, censusing cryptic, slow moving arboreal mammals in dense forest is challenging and limited. For instance, a census carried out on existing mangrove tracts in Isla Escudo de Veraguas (0.02% of the island area) sighted a total of 79 individuals, 70 of which were in the mangroves and nine in non-mangrove trees in the periphery of the mangroves (Kaviar et al. 2012). However, no estimates on the total island population were made; the population is likely to be relatively small. In the mangroves the population density of this sloth is relatively high (5.8 sloths/ha).

Population Trend
Decreasing
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Threats

Major Threats
Although the island is uninhabited, there are seasonal visitors (fishermen, campesinos, lobster divers, tourists, and local people) who harvest timber to maintain wooden houses on the island. Preliminary studies suggest a reduced level of genetic diversity for pygmy sloths compared to its putative population of origin, the common sloth population from mainland Panama. This is expected, considering the history of species diversification and isolation on the island. However, signs of a more recent population bottleneck were also detected (Silva et al. 2010, N. Moraes-Barros pers. comm. 2013). These results highlight the need of a continuous evaluation of the population status, trends, and additional studies considering a possible scenario of endogamic depression if the (already low) population size decreases any further.

Despite having been designated as a protected landscape through a governmental resolution in 2009, a number of domestic and international efforts have been mounted to develop tourism infrastructure on the island. This includes plans for an eco-lodge, a casino, a marina, and a banking centre. The current status of the island’s custody is vague; a governmental resolution, and thus the protected status of the island, cannot be revoked, but no government staff has been appointed specifically to enforce protection of the island. Ongoing disagreements between the local Ngäbe bugle Comarca, regional politicians, and the Panamanian government are further complicating long-term protection of the island and the pygmy sloths. Additionally, as pygmy sloths have become more widely recognized internationally, there is growing interest in collecting them for captivity.
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The pygmy three-toed sloth has an extremely restricted range on one very small island. Although the island is uninhabited, fishermen, farmers, lobster divers and local people are all seasonal visitors, and are thought to hunt the sloths illegally. The growing tourism industry is also a potential threat to the species, by degrading its habitat (1).
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Management

Conservation Actions

Conservation Actions
Bradypus pygmaeus is endemic to a single island of Panama, which is protected as a wildlife refuge and is contained within the Ngäbe bugle Comarca. There is a need to improve the enforcement of this protected area. A comprehensive conservation plan is underway, bringing together the local community, wildlife authorities in Panama, and the national and international scientific community to protect the island, using the pygmy sloth as a flagship species.

The pygmy sloth is listed on CITES Appendix II (Notification to the Parties 2013/052, 20 November 2013).
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Conservation

Isla Escudo de Veraguas is protected as a wildlife refuge and is contained within the Comarca Indigenous Reserve. However, law enforcement within this protected area is currently inadequate, and needs to be improved (1).
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Relevance to Humans and Ecosystems

Benefits

There are no known adverse effects of Bradypus pygmaeus on humans.

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There are no known benefits to humans from Bradypus pygmaeus at this time.

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