SLOTH

Three-toed sloth (Bradypus tridactylus) tree-dwelling mammal belonging to the family Bradypodidae and placed with armadillos and anteaters in the order Edentata. The six living species are found in tropical South and Central America. Their extinct relatives, the ground sloths, once ranged into areas of the North American continent. Sloths have rounded heads, inconspicuous ears, and flattened faces. The head and body are about 6070 cm (2427 inches) long, and the tail is short or rudimentary. The forelimbs are longer than the hind limbs, with long, curved claws sharp enough to cause deep wounds. The four species of three-toed sloths, or ais (Bradypus), have three toes on each limb; the two species of two-toed sloths, or unaus (Choloepus), have two on the forelimbs but three on the hind limbs. Although most mammals have seven neck vertebrae, three-toed sloths have nine, and two-toed sloths have six or seven. Three-toed sloths can turn the head through a 270 arc. Sloths seldom voluntarily descend to the ground. Because they cannot walk but must pull themselves along the ground with their claws, they are easy prey for jaguars and other predators. They cling erect to tree trunks and branches or hang upside down and move with extreme slowness, hand over hand, through the trees, feeding on the vegetation. They are nocturnal and are generally solitary, fighting off others of the same sex. Sloths can swim well and are able to survive immersion better than other land mammals. In the trees they are well camouflaged among the leaves, especially during the rainy season, when a green alga grows among their stiff, brownish hairs. Generally silent, they can utter a shrill cry or a hiss. A single young is born after about four to six months' gestation and clings to the fur of the mother from birth until about five weeks of age. In captivity the unau has lived more than 20 years; the ai rarely survives more than a few months, partly because of its apparent dietary restriction to the leaves of a trumpet tree (Cecropia).