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 sloths, with both males and females being 42 to 80 cm (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.
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, Brazil 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.
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.
Brown-throated sloths have a polygynous mating system. 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.
In the wild, the lifespan of adult brown-throated three-toed sloths is typically between 30 and 40 years.
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.
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 )
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
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
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 )
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
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.
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 ; 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.
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)
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
There are no known adverse effects of Bradypus variegatus on humans.
There are no known positive effects of Bradypus variegatus on humans.