Bradypus is a terrestrial mammal of the sloth family, which is often characterized by its slow-moving demeanor and coarse hair. Although Bradypus variegatus has similar features to other bradypodidae, as a species it can be clearly distinguished by the brown coloration along the “sides of its face and throat, prominent dark brown forehead, suborbital stripe outlining the ocular area of the face and shorter mandibular spout”(1). Found in the forest canopies of Central and South America, the brown-throated three-toed sloth feeds off of leaves and shoots, descending from the treetops every eight days to defecate(1). Home ranges vary in size from 0.5 to 9 hectares, and sloths are said to spend time in an average of 40 trees for every 5 hectares(2). A portion of Bradypus variegatus’ home range is passed on from mother to baby sloth for competition reduction. Mating season occurs annually before the start of the rainy season, and one offspring per litter is born after an estimated gestation period of 4-6 months(3).
Aptly named for its three distinct claws, the three-toed sloth is an unusual looking mammal best known for its sloth (slow) movements throughout its forest habitat. In terms of color and fur, Bradypus variegatus has grey-brown fur, which grows “ventral to dorsal, opposite than most mammals, providing quick rain runoff”(3). A finer layer of fur grows beneath for further insulation from the elements(3). Unusually, the sloth’s fur changes to a green tinged color during the rainy season because of the algae that grows in the grooves on its hairs; this provides further protection and camouflage from its predators(2). Males differ from females in that they have “an orange patch [of hair] that contains a brown stripe through the middle”(3) Bradypus variegatus has a small head, tail, and facial features as well as limited eyesight and hearing(1).
Aptly named for its three distinct claws, the three-toed sloth is an unusual looking mammal best known for its sloth (slow) movements throughout its forest habitat. In terms of color and fur, Bradypus variegatus has grey-brown fur, which grows “ventral to dorsal, opposite than most mammals, providing quick rain runoff”(2). A finer layer of fur grows beneath for further insulation from the elements(2). Unusually, the sloth’s fur changes to a green tinged color during the rainy season because of the algae that grows in the grooves on its hairs; this provides further protection and camouflage from its predators. Males differ from females in that they have “an orange patch [of hair] that contains a brown stripe through the middle”(2). Bradypus variegatus has a small head, tail, and facial features as well as limited eyesight and hearing(1).
Brown-throated three-toed sloths are native to South America and southern Central America. Their geographic range includes Bolivia, Brazil, Columbia, Ecuador, Honduras, Nicaragua, Panama, Paraguay, Peru, and Venezuela. Although once present in Argentina, it is now thought to be extinct.
Biogeographic Regions: neotropical (Native )
- Chiarello, A. 2008. "Bradypus variegatus" (On-line). The IUCN Red List of Endangered Species. Accessed March 12, 2011 at http://www.iucnredlist.org/apps/redlist/details/3038/0.
There are no confirmed records for B. variegatus in the Pantanal biome of Brazil, but the species might occur in the contact zones between this biome and the Amazon forest to the north. Additional field studies are necessary in order to properly define the current species distribution in the Cerrado, Caatinga and Pantanal.
The southernmost distribution of this sloth in Brazil was reported by Cabrera (1957) as the state of Rio Grande do Sul, which could, however, not be confirmed (Gardner 2007). It is historically absent from the state of Santa Catarina (Brazil) and northeastern Argentina; the southernmost confirmed record of the species is near Londrina, in the state of Paraná, Brazil, but today it is considered extinct in this state (Mikich and Bernils 2004). The last record from Argentina was collected in Jujuy province and dates back to 1916 (Vizcaíno et al. 2006), but field studies specifically aiming at this species are lacking from this country. Bradypus variegatus is found from sea level to at least 2,400 m asl (Ureña et al. 1986).
Brown-throated three-toed sloths can be found throughout Central and South America, ranging as far north as Honduras and as far south as Brazil(4). They are native to Nicaragua, Paraguay, Venezuela, Peru, Bolivia, Costa Rica, Brazil, Ecuador, Panama, Argentina, Columbia, and Honduras, but their population density within each habitat varies(4). In Panama, for example there are an estimated 8.5 animals per hectare, whereas in Costa Rica, an estimated 9.9 dwell per hectare(4).
As indicated by their common, brown-throated three-toed sloths have brown coloration on their throat and head. Their coat consists of a layer of short, soft, and fine fur and a layer of thick, woolly fur. Algae often resides on outer layer, giving some individuals a greenish appearance. They have long forelimbs with three clawed-toes on each limb. They also have approximately 10 cervical vertebrate that enable them to rotate their necks up to 270 degrees. Their teeth are cylindrical and lack enamel. Similar to many ungulates, their stomachs are multi-compartmentalized, with intestinal microfauna that help digest cellulose from their exclusively vegetarian diets. Even as endotherms, brown-throated three-toed sloths have difficulty regulating their body temperature in cold environments and in cooler ambient temperatures. This is likely due to sparse muscle mass, their relatively small heart, and low-ranging heart rate. Adults range in mass from 3.49 to 5.19 kg, with an average of 4.34 kg. Average length is 60 cm, and they have a basal metabolic rate of 147 cm^3 oxygen/hour. Although size-dimorphism is not present in this species, males have a mid-dorsal speculum that is not present in females.
Range mass: 3.49 to 5.19 kg.
Average length: 60 cm.
Average basal metabolic rate: 147 cm3.O2/g/hr.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes colored or patterned differently
- Feldhamer, G., L. Drickamer, S. Vessey, J. Merritt. 2007. Mammalogy: Adaptation, Diversity, Ecology. Maryland: Johns Hopkins University Press.
- Gilmore, D., C. Da Costa, D. Duarte. 2001. Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses. Brazilian Journal of Medical and Biological Research, 34: 9-25.
- Gilmore, D., C. Da-Costa, D. Duarte. 2000. An update on the physiology of two- and three-toed sloths. Brazilian Journal of Medical and Biological Research, 33: 129-146. Accessed February 22, 2011 at http://www.scielo.br/pdf/bjmbr/v33n2/3528c.pdf.
Rio Negro-Rio San Sun Mangroves Habitat
This taxon occurs in the Rio Negro-Rio San Sun mangroves, which consists of a disjunctive coastal ecoregion in parts of Costa Rica, extending to the north slightly into Nicaragua and south marginally into Panama. Furthermore, this species is not necessarily restricted to this ecoregion. Mangroves are sparse in this ecoregion, and are chiefly found in estuarine lagoons and small patches at river mouths growing in association with certain freshwater palm species such as the Yolillo Palm (Raphia taedigera), which taxon has some saline soil tolerance, and is deemed a basic element of the mangrove forest here. These mangrove communities are also part of a mosaic of several habitats that include mixed rainforest, wooded swamps, coastal wetlands, estuarine lagoons, sand backshores and beaches, sea-grasses, and coral reefs.
The paucity of mangroves here is a result of the robust influx of freshwater to the coastline ocean zone of this ecoregion. Among the highest rates of rainfall in the world, this ecoregion receives over six metres (m) a year at the Nicaragua/ Costa Rica national border. Peak rainfall occurs in the warmest months, usually between May and September. A relatively dry season occurs from January to April, which months coincides with stronger tradewinds. Tides are semi-diurnal and have a range of less than one half metre.
Mangroves play an important role in trapping sediments from land that are detrimental to the development of both coral reefs and sea grasses that are associated with them. Mangrove species including Rhizopora mangle, Avicennia germinans, Laguncularia racemosa, Conocarpus erecta and R. harrisonii grow alone the salinity gradient in appropriate areas. Uncommon occurrences of Pelliciera rhizophorae and other plant species associated with mangroves include Leather ferns Acrostichum spp., which also invade cut-over mangrove stands and provide some protection against erosion. In this particular ecoregion, the mangroves are associated with the indicator species, freshwater palm, Raphia taedigera. Other mangrove associated species are Guiana-chestnut ( Pachira aquatica) and Dragonsblood Tree (Pterocarpus officinalis).
Reptiles include the Basilisk Lizard (Basiliscus basiliscus), Caiman (Caiman crocodilus), Green Sea Turtle (Chelonia mydas), Leatherback Turtle (Dermochelys coriacea) and Green Iguana (Iguana iguana). The beaches along the coast within this ecoregion near Tortuguero are some of the most important for nesting green turtles. The offshore seagrass beds, which are among the most extensive in the world, are a source of food and refuge for the endangered Green Sea Turtle (Chelonia mydas). Several species of frogs of the family Dendrobatidae are found in this mangrove ecoregion as well other anuran species and some endemic salamander taxa.
Mammal species found in this highly diverse ecoregion include: Lowland Paca (Agouti paca), primates such as Mantled Howler Monkey (Alouatta palliata), Geoffrey's Spider Monkey (Ateles geoffroyi), White-faced Capuchin (Cebus capucinus), Brown-throated Sloth (Bradypus variegatus), Silky Anteater (Cyclopes didactylus) and Nine-banded Armadillo (Dasypus novemcintus). Also found in this ecoregion are carnivores such as Ocelot (Leopardus pardalis), Central American Otter (Lutra annectens), Jaguar (Panthera onca), Northern Racooon (Procyoon lotor), and Crab-eating Racoon (P. cancrivorus).
Brown-throated three-toed sloths can be found in many new-world tropical forests, though some have also been discovered in semi-deciduous forests and subtropical lowlands and swamps. They live in the canopy for the majority of their lives and are capable swimmers. They seldom travel on the ground. They can be found at elevations ranging from sea level to 2400 m. Although not selective about the species of tree they choose to inhabit, they tend to seek out trees with crowns that are highly exposed to sunlight. This preference has been attributed to the sloths using sunlight to fulfill their thermoregulatory needs.
Range elevation: 0 to 2400 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest ; rainforest
Aquatic Biomes: rivers and streams
Other Habitat Features: riparian
- 2008. "Brown-throated three-toed sloth (Bradypus variegatus)" (On-line). World Association of Zoos and Aquariums - United For Conservation. Accessed March 12, 2011 at http://www.waza.org/en/zoo/visit-the-zoo/sloths-anteaters-armadillos-pangolins-and-aardvark/bradypus-variegatus.
Habitat and Ecology
Bradypus variegatus is a tree dweller of the humid, subtropical areas of Central and South America(1). “The crowns of the trees in tropical forests are often thick with interlocking lianas and other vegetation and provide strong footholds for sloth travel, sleeping, and mating”(1). Because Bradypus spends the near entirety of its time hanging from tree limbs in the middle to upper layers of the canopy, it prefers more densely wooded areas, which allow for migration from one tree to the next. With that in mind, “Bradypus prefers trees with large crowns and selects them based on the amount of time the crowns are exposed to sun,” mostly because of its low body temperature and dependence on external sources of heat(1).
Bradypus variegatus is a strict herbivore that feeds primarily on trees in the genus Cercropia (e.g., embauba). They consume various parts of the tree, including leaves, flowers, and fruits. Bradypus variegatus is a facultative drinker and receives most of its water from ingested plant materials.
Plant Foods: leaves; fruit; flowers
Primary Diet: herbivore (Folivore , Frugivore )
The brown-throated sloth eats various leaves and foliage in its habitat, however the majority of its diet is supplied by Cecropia trees which also tend to be located in prime locations for such limited organisms (by clearings and riverbanks)(1). Most of the water these sloths need comes from the leaves that they eat(1). Bradypus variegatus’ hooked claws allow it to pull leaves towards its mouth(1).
Brown-throated three-toed sloths have are mutualists with algae, which reside in the coats of sloths. The presence of algae confers a greenish tint to the outermost fur coat, which is hypothesized to function as camouflage. It has also been suggested that algae provides essential trace elements and nutrients. In exchange, algae receives shelter in the coats of their host and sunlight, as sloths prefer sections of sun-exposed canopy. Brown-throated three-toed sloths are primary prey for a number of vertebrate predators including harpy eagles and many species of felid; however, they do not make up a large portion of any one species' diet. Known parasites of this species include Leishmania and Pneumocystis carinii.
Ecosystem Impact: creates habitat
- algae, (Chlorophyta)
- algae, (Chrysophyta)
- algae, (Cyanophyta)
- algae, (Rhodophyta)
- trypanosomatid protozoans, (Leishmania)
- fungus, (Pneumocystis carinii)
Brown-throated three-toed sloths are highly camouflaged and slow-moving, both of which help decrease risk of predation via decreased visibility. Major predators of this species include spectacled owls, harpy eagles and a variety of felid species. Brown-throated three-toed sloths descend from the canopy to defecate and urinate on the ground. Although they only descend from teh canopy once every 3 to 8 days, this behavior greatly increases vulnerability to predation.
- spectacled owls, (Pulsatrix perspicillata)
- harpy eagle, (Harpia harpyja)
- felids, (Felidae)
Anti-predator Adaptations: cryptic
- Touchton, J., Y. Hsu, A. Palleroni. 2002. FORAGING ECOLOGY OF REINTRODUCED CAPTIVE-BRED SUBADULT HARPY EAGLES (HARPIA HARPYJA) ON BARRO COLORADO ISLAND, PANAMA. ORNITOLOGIA NEOTROPICAL, 13: 365–379.
- Voirin, J., R. Kays, M. Lowman, M. Wikelski. 2009. Evidence for Three-Toed Sloth (Bradypus variegatus) Predation by Spectacled Owl (Pulsatrix perspicillata). Edentata, 8-10: 15-20.
Life History and Behavior
Social interactions between Bradypus variegatus adults are relatively rare. However, communication between mothers and their young is significant, particularly in the form of vocalization. Vocalizations are also used to communicate with other conspecifics during breeding season, as females call out to attract a potential mate. Bradypus variegatus lack a ciliary muscle in their eyes and have very few ganglion cells and nerve fibers, which result in poor eyesight and visual acuity. Evidence suggests that vision functions optimally at low light intensities. Defecation and urination occur on the ground, and both have been suggested to function as a means of communicating with other conspecifics.
Communication Channels: visual ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
In the wild, the lifespan of adult brown-throated three-toed sloths is typically between 30 and 40 years. There is no other information available regarding the lifespan of this species.
Status: wild: 30 to 40 years.
Status: wild: 30 to 40 years.
- MORAES-BARROS, ., J. SILVA, J. MORGANTE. 2011. Morphology, molecular phylogeny, and taxonomic inconsistencies in the study of Bradypus sloths (Pilosa: Bradypodidae). Journal of Mammalogy, 92: 86-100.
Brown-throated three-toed sloths are thought to be monogamous. Females vocalize to attract males when they are ready to mate. Females typically mate with the first male they encounter. Although it is unclear if they have a defined breeding season, evidence suggests mating occurs just prior to the rainy season. Copulation lasts 10 to 15 minutes and takes place in the female's tree, approximately 15 m above the ground. During copulation, the male positions himself behind the female. Once mating is complete, the male leaves shortly there after.
Mating System: monogamous
Once copulation is finished, males immediately leave and do not provide any parental care to young. Bradypus variegatus gives birth to a single offspring once a year. During gestation, which lasts for 5 to 8 months, the mother does not make any preparations, such as nest-building. After birth, neonates are held ventrally, which is thought to help provide protection for young, including attack from predators. Neonates weigh less than 1 kg at birth. Most individuals become independent once weaning is complete, which takes approximately 4 months. Females become reproductively mature by 3 years of age, and males become reproductively mature between 3 and 5 years of age, with an average of 4 years of age.
Breeding interval: Brown-throated three-toed sloths breed once yearly
Average number of offspring: 1.
Range gestation period: 5 to 8 months.
Average weaning age: 4 months.
Range time to independence: 2 to 4 months.
Average age at sexual or reproductive maturity (female): 3 years.
Range age at sexual or reproductive maturity (male): 3 to 5 years.
Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Brown-throated three-toed sloths give birth on the ground or in trees. During birth, the mother pulls the infant between her hindlegs, and other sloths aid in the birthing process by cleaning the mother and infant and by ensuring that the infant doesn't fall. Mothers help young establish motor behavior, posture, learning development, and independent exploration in young. Paternal care is thought to be non-existent in this species.
Parental Investment: female parental care ; pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)
- Bezerra, B., A. Souto, L. Halsey, N. Schiel. 2007. Observation of brown-throated three-toed sloths: mating behaviour and the simultaneous nurturing of two young. Japan Ethological Societ, 26: 175–178.
- Gilmore, D., C. Da-Costa, D. Duarte. 2000. An update on the physiology of two- and three-toed sloths. Brazilian Journal of Medical and Biological Research, 33: 129-146. Accessed February 22, 2011 at http://www.scielo.br/pdf/bjmbr/v33n2/3528c.pdf.
- SOARES, C., R. CARNEIRO. 2002. SOCIAL BEHAVIOR BETWEEN MOTHERS ´ YOUNG OF SLOTHS Bradypus variegatus SCHINZ, 1825 (XENARTHRA: BRADYPODIDAE). Brazilian Journal of Biology, Volume 62, Issue 2: 249-252.
Evolution and Systematics
The head of the three-toed sloth swivels 270 degrees thanks to three extra cervical vertebrae.
"Because the three-toed sloth has three extra cervical vertebrae than other mammals, including its close relative the two-toed sloth, it is able to turn its head 270 degrees, or three-quarters the way around." (Young 1999)
Learn more about this functional adaptation.
Young, Amy. 1999. Bradypus variegatus. University of Michigan Museum of Zoology.
Bradypus variegatus is classified as a species of least concern on the IUCN's Red List of Threatened Species. Although precise population trends are unknown, is has been estimated that densities ranging from 2.2 to 8.5 animals per hectare occur throughout their geographic range. Although some populations in the Brazilian Amazon are thought to be declining due to deforestation, there are no major threats to the long-term persistence of this species.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2013Least Concern
- 2006Least Concern(IUCN 2006)
- 2006Least Concern
Recent phylogeographic studies reveal that B. variegatus from the Central American, Western Amazon and Atlantic forests constitute distinct and unique evolutionary units that are distinguishable by molecular and morphological traits.
Predators of the brown-throated sloth include jaguars, harpy eagles, and anacondas(1). There are few other threats to the sloth aside from deforestation and humans trespassing on sloth habitat(7).
Relevance to Humans and Ecosystems
There are no known adverse effects of Bradypus variegatus on humans.
There are no known positive effects of Bradypus variegatus on humans.
The brown-throated sloth (Bradypus variegatus) is a species of three-toed sloth found in the neotropical ecozone. It is the most common of the four species of three-toed sloth, and is found in the forests of South and Central America.
The brown-throated sloth is of similar size and build to most other species of three-toed sloth, with both males and females being 42 to 80 centimetres (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.
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.
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.
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. Sloth hair also harbours a rich fungal flora.
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.
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, and eastern Peru. It is probably not found 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.
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 a few brief periods, 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. Adult animals are solitary, except when raising young, and males have been observed to fight one another using their fore claws.
Brown-throated sloths inhabit the high canopy of the forest, where they eat young leaves from a wide range of different trees. 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.
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. 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.
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.
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.
The female's mammary glands do not store significant quantities of milk as most other mammals do, since the lactating infant sloth remains attached to the nipple at all times, and consumes the milk as soon as it is generated. 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.
Brown-throated sloths have lived for at least three years in captivity.
- 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 seven million years ago.
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