Sloths are beloved for being the world's slowest mammal, so sedentary that algae grow on its furry coat. The plant gives it a greenish tint that is useful camouflage in the trees of its Central and South American rain forest home. There are two different types of sloths: two-toed and three-toed. Like other three-toed sloths, the brown-throated sloths (Bradypus variegatus) have an advantage that few other mammals possess: They have extra neck vertebrae that allow them to turn their heads some 270 degrees.All sloths are built for life in the treetops. They spend nearly all of their time aloft, hanging from branches with a powerful grip aided by their long claws. (Dead sloths have been known to retain their grip and remain suspended from a branch.) Sloths even sleep in trees, and they sleep a lot—some 15 to 20 hours every day. Even when awake they often remain motionless. At night they eat leaves, shoots, and fruit from the trees and get almost all of their water from juicy plants. Surprisingly, sloths are excellent swimmers, occasionally dropping from their treetop perches into water for a paddle.