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).

B. variegatus ranges from Honduras in the north, through southern Central America. In South America, it ranges from Colombia into western and southern Venezuela, and south into Ecuador, eastern Peru and Bolivia, into Brazil and northern Argentina (where it is now considered to be extirpated). Its distribution overlaps with B. torquatus in the central part of the Atlantic forest (Hirsch and Chiarello unpublished data). In Brazil, the species currently occurs in forested areas of the Amazon, Atlantic forest, and Cerrado biomes. There are historical records of B. variegatus in the Caatinga biome (Moraes-Barros unpublished data 2010).
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. B. variegatus is found from sea level to at least 2,400 m asl (Ureña et al. 1986).

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 )

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 cm^3 oxygen/hour.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes colored or patterned differently

Habitat and Ecology

Systems

• Terrestrial

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

Wetlands: swamp

Other Habitat Features: riparian

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

Mutualist Species:

• algae, (Chlorophyta)
• algae, (Chrysophyta)
• algae, (Cyanophyta)
• algae, (Rhodophyta)

Commensal/Parasitic Species:

• 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.

Known Predators:

• spectacled owls, (Pulsatrix perspicillata)
• harpy eagle, (Harpia harpyja)
• felids, (Felidae)

Anti-predator Adaptations: cryptic

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 ; acoustic

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.

Range lifespan

Status: wild: 30 to 40 years.

Typical lifespan

Status: wild: 30 to 40 years.

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 birth mass: less than 1 kg.

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); 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)

Neck swivels 270 degrees: three-toed sloth
 

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.

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

Population

Population Trend

Major Threats

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).

Conservation Actions

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

There are no known positive effects of Bradypus variegatus on humans.