Slow-moving South American mammal, about 70 cm/2.5 ft long, family Bradypodidae, order Edentata. Sloths are greyish brown and have small rounded heads, rudimentary tails, and prolonged forelimbs. Each foot has long curved claws adapted to clinging upside down from trees. On the ground the animals cannot walk, but drag themselves along. They are vegetarian.

The hair is brown, long, coarse and shaggy. An alga lives in it, and in damp weather turns the hair green, which helps the animal to blend in with its leafy background. Sloths are nocturnal animals. They usually live alone in the treetops, eating leaves. They give birth to one young at a time, which spends its first few weeks clinging to its mother's hair.

Species
There are six living species in two genera. Bradypus has four species of three-toed sloths, including B. tridactylus. They have nine vertebrae in their necks instead of the usual mammalian seven, and can turn their heads almost completely around to see behind them. Choloepus contains two species of two-toed sloths, including C. didactylus of northern South America.