Sloth

Sloth, common name for certain slow-moving arboreal (tree-dwelling) mammals that inhabit the tropical forests of South and Central America. Sloths are divided into two groups: the three-toed sloths, among which is the ai, and the two-toed sloths, among which is the unau. Sloths are usually about 41 to 74 cm (16 to 29 in) long. The flat, short head has large eyes, a snub nose, and rudimentary ears. The entire body is covered with greyish-brown, short hair. The tail is small in three-toed sloths and absent or vestigial in two-toed sloths. An ancestral form, the giant ground sloth, which lived in the Western hemisphere more than 10,000 years ago, reached the size of an elephant.

Sloths are relatively long-lived, sometimes living for more than 20 years. They spend their entire existence hanging suspended from the boughs of trees, with the legs and face turned upward and the back downward. The limbs are long and well developed, and terminate in long, curved claws that hook over and grasp the supporting bough. The forelimbs are longer, better developed, and more mobile than the hindlimbs, particularly in the three-toed sloths. The animal moves by advancing one limb at a time in a slow, deliberate fashion. Sloths descend to the ground only about once each week in order to defecate and urinate. When placed on the ground they lie on their backs or crawl with the greatest difficulty.

The sloth sleeps during the day, curled up with the feet drawn close together and the head placed between the forelimbs. In this position the animal resembles a stump of a bough and is relatively well camouflaged from the assault of natural enemies such as the jaguar. An incrustation of a green alga, which forms in the hair of some species and makes them indistinguishable from the surrounding foliage and moss, affords additional protection. The animal is habitually silent but sometimes utters a low, plaintive call. It feeds chiefly on foliage and shoots, which are pulled within reach of the mouth with typical slow movements. Each year the female produces a single offspring, which clings to the mother until it can take care of itself.

Scientific classification: Sloths belong to the order Xenarthra. Three-toed sloths make up the genus Bradypus in the family Bradypodidae. The ai is classified as Bradypus tridactylus. Two-toed sloths make up the genus Choloepus in the family Megalonychidae. The unau is classified as Choloepus hoffmanni.