The brown-throated sloth (Bradypus variegatus) is a species of three-toed sloth found in the Neotropical realm of Central and South America.
It is the most common of the four species of three-toed sloth, and is found in the forests of South and Central America.
Description
The brown-throated sloth is of similar size and build to most other species of three-toed sloths, with both males and females being in total body length. The tail is relatively short, only long. Adults weigh from , with no significant size difference between males and females. Each foot has three fingers, ending in long, curved claws, which are long on the fore feet, and 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. Certain strains of fungi that grow on brown-throated sloth fur have been shown to possess anti-parasitic, anti-cancer, and anti-bacterial qualities.
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, Brazil and eastern Peru. It is probably not found immediately 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 , 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 brief periods of time, 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. The brown-throated sloths are cathemeral, with no preference for sleeping at day or night. Large, curved claws and muscles specifically adapted for strength and stamina help them to keep a strong grip on tree branches. They are able to withstand hanging inverted for extended periods of time due to fibrinous adhesions which attach their organs (such as their liver and stomach) to their lower ribs. Given that feces and urine can account for up to a third of their body weight, this adaptation prevents these organs from pressing on the lungs when hanging upside down, making breathing easier. 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 (primarily in the genus Cecropia), as well as flowers and fruits. They do not travel far, with home ranges of only around , depending on the local environment. Within a typical, 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. Although they get most of their fluids from the leaves that they eat, brown-throated sloths have been observed drinking directly from rivers.