Sloths are slow because they have extremely low metabolic rates. In other words, they have very little energy and move slowly in order to conserve the energy that is available. This is due in part to their herbivorous diets.
Sloths, which are the slowest mammals on earth, are found in the tropical rainforests of Central and South America. They travel, at most, only about 40 yards per day. Aside from their slow metabolic rate, sloths also have significantly less muscle tissue compared to other types of mammals of similar size, resulting in their having less strength and mobility. Sloths are so slow, in fact, that algae grows on the outer layer of their fur, providing them with camouflage while in the trees.
There are six species of sloths. They sleep for most of the day, sometimes for up to 20 hours. Sloths are arboreal, spending most of their lives in the tree canopies, thanks in part to their long claws that help them grip and move between limbs where they eat leaves, shoots and fruit. Though they are excellent swimmers, sloths get most of their water from the fruit they eat. Their long claws make it difficult for sloths to move along the ground. They only come down about once a week to urinate and defecate and perhaps also to leave a scent for other sloths to find during mating.