A fully arboreal mammal that walks on the ground only with difficulty, spending its life hanging upside down from tree branches by means of its large, curved claws. A sloth has a short, rounded head, long limbs, and long, coarse, grooved fur that grows away from the animal’s extremities so that rainwater drains from it. The fur hosts cyanobacteria and other organisms, giving the sloth a greenish colour. A sloth moves as little as possible and then slowly, feeds on leaves, and comes to the ground about once a week to urinate and defecate. There are two families, Bradypodidae of three-toed sloths comprising four species, and Megalonychidae of two-toed sloths comprising two species. Sloths occur in Central and South American tropical rainforests.