Sloths—the sluggish tree-dwellers of Central and South America—spend their lives in the tropical rain forests. They move through the canopy at a rate of about 40 yards per day, munching on leaves, twigs and buds. Sloths have an exceptionally low metabolic rate and spend 15 to 20 hours per day sleeping. And surprisingly enough, the long-armed animals are excellent swimmers. They occasionally drop from their treetop perches into water for a paddle.