Three-Toed Sloth

Life in Slow Motion

The pale-throated three-toed sloth (Bradypus tridactylus) is found in the forests of Venezuela, Guyana, Suriname, French Guiana and northern Brazil. Adults average about 4.25 kg, and three-toed sloths in general grow 1.5 to 2.5 feet (46 to 76 cm) long. Three-toed sloths live high in the rainforest canopy and feed on the twigs, buds and leaves of Cecropia trees. They need relatively little food and run a lower metabolic rate than other mammals of similar size, and at night a sloth’s body temperature drops to save energy. No detailed study of its lifespan exists, but it has been estimated to live up to 40 years in the wild. The Red List rated it Least Concern in 2022, though its population is decreasing.

A Fur Coat Full of Neighbors

Sloths carry a complex community of organisms in their hair, including moths and algae, and green algae living in the hair can give a sloth an overall greenish look that camouflages it in the canopy. In 1977, Wulf Koch, curator of an algae collection at Germany’s University of Göttingen, isolated one of those algae from the hairs of a pale-throated sloth in Brazil’s Amazon. It was filed under the name Trichophilus welckeri. In 2024, scientists re-examined its shape and DNA and found it belonged in a different genus. They described it as a new species and named it Prasiolopsis wulf-kochii, after him.

Ground Rules

Climbing down to defecate on the ground puts a sloth at risk from predators, and scientists have proposed at least five explanations for why sloths do it. One is a partnership with fur moths: the sloth covers its droppings to benefit moth larvae that develop inside them. That model was built on the brown-throated three-toed sloth (Bradypus variegatus), a close relative, and a 2021 review found it contradicted by the scientific literature. The pale-throated sloth may not even follow the same script.

Business from the branches Bradypus tridactylus sometimes relieves itself straight from the canopy, and the review’s author suggests it may be on its way to a more fully tree-bound life.

It is usually a loner: during a wildlife rescue along French Guiana’s Sinnamary River, over 73 percent of the pale-throated sloths captured were solitary. Three-toed sloths defend themselves from predators like jaguars with long arms, sharp claws and sharp teeth. On the rare occasions one comes down to the ground, it drags itself along by its hands. It can stand on its feet but cannot walk on them. In water, though, it is an excellent swimmer.