Description

The three-toed sloth is an arboreal mammal found throughout Central and South America. Its namesake is one of the seven deadly sins (sloth) and ‘three-toed’ refers to its three claws on each limb. There are four species of three-toed sloths, two of which are found in the Amazon rainforest. The brown-throated sloth (Bradypus variegatus) is the most widely distributed three-toed sloth. Its range spans as far north as Honduras, through Central America and encompasses the entire Amazon rainforest and beyond to the eastern coast of Brazil in the Atlantic rainforest.

Habitat

Three-toed sloths inhabit forests of many types including cloud and lowland tropical forest in the Amazon, though they also occasionally reside in cacao plantations [1]. They spend most of their time hanging from branches high up in the rainforest canopy, where they eat, sleep, mate and even give birth.

Behavior and Diet

Rightly or wrongly, sloths have gained a reputation as the laziest members of the animal kingdom. In captivity they may sleep 15-20 hours a day, but in the wild they only sleep on average about 9.6 hours a day [2]. However, it is true that sloths are among the slowest-moving mammals in the world, moving on average only about half the length of a football field (41 yards) per day [3].

Sloths are folivores, meaning they exclusively consume leaves, twigs and buds, and eat the leaves of close to 30 different tree and liana (woody vines) species. To aid in the breakdown of such tough material, they have four-part stomachs and highly specialized gut bacteria, similar to digestive systems in other ruminants such as domestic cattle. Given their diet, it is not surprising sloths have an incredibly slow metabolism and low percent muscle mass compared to other mammals. What first may appear to be a lazy lifestyle is actually a successful evolutionary adaptation: sloths are morphologically and physiologically specialized to live in the high canopy and consume foods low in nutritional value that many other mammals would not be able to thrive on.

Threats

Though the conservation status of both species of three-toed sloths in the Amazon are currently listed as ‘Least Concern’ by the IUCN, they do face threats such as capture by humans for illicit pet trade, and they are also hunted to be sold as food and medicine [4]. Deforestation and habitat fragmentation threaten sloths like all other Amazonian creatures. Lack of forest cover deprives them of their food source and renders them defenseless against predation on open ground – sloths are not agile on land and would be easy prey for jaguars and other big cats.

Ecological Importance

Sloths are integral components of the Amazon rainforest. They foster a symbiotic relationship with a species of algae found only on sloths and nowhere else [5]! The relationship is beneficial to both: the algae gains shelter and water in the sloth’s hair, while providing the sloth with camouflage, protecting it from predators. Algae aren’t the only opportunists taking up residence in sloths – recent research has discovered that a number of fungi inhabiting sloths have disease-fighting properties [6].

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