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Feeding Brown-throated Three-toed Sloth (Bradypus variegatus), Cahuita National Park, Costa Rica Sloths are classified as folivores as the bulk of their diet consists mostly of buds, tender shoots, and leaves, mainly of Cecropia trees. Some two-toed sloths have been documented as eating insects, small reptiles and birds as a small supplement to their diet. Linnaeus's Two-toed Sloth has recently been documented eating human faeces from open latrines. They have made extraordinary adaptations to an arboreal browsing lifestyle. Leaves, their main food source, provide very little energy or nutrition and do not digest easily. Sloths therefore have very large, specialized, slow-acting stomachs with multiple compartments in which symbiotic bacteria break down the tough leaves. As much as two-thirds of a well-fed sloth's body-weight consists of the contents of its stomach, and the digestive process can take a month or more to complete. Even so, leaves provide little energy, and sloths deal with this by a range of economy measures: they have very low metabolic rates (less than half of that expected for a mammal of their size), and maintain low body temperatures when active (30 °C (86 °F) to 34 °C (93 °F)), and still lower temperatures when resting. Although unable to survive outside the tropical rainforests of South and Central America, within that environment sloths are outstandingly successful creatures: they can account for as much as half the total energy consumption and two-thirds of the total terrestrial mammalian biomass in some areas. Of the six living species, only one, the Maned Three-toed Sloth (Bradypus torquatus), has a classification of "endangered" at present. The ongoing destruction of South America's forests, however, may soon prove a threat to other sloth species.  Physiology
Sloth furs exhibit specialized functions: the outer hairs grow in a direction opposite from that of other mammals. In most mammals, hairs grow toward the extremities, but because sloths spend so much time with their legs above their bodies, their hairs grow away from the extremities in order to provide protection from the elements while the sloth hangs upside down. In most conditions, the fur hosts two species of symbiotic cyanobacteria, which provide camouflage. Because of the cyanobacteria, sloth fur is a small ecosystem of its own, hosting many species of non-parasitic insects. Sloths have short, flat heads; big eyes; a short snout; long legs; and tiny ears. They also have stubby tails, usually 6–7 cm long. Altogether, sloths' bodies usually are anywhere between 50 and 60 cm long. Sloths' claws serve as their only natural defense. A cornered sloth may swipe at its attackers in an effort to scare them away or wound them. Despite sloths' apparent defenselessness, predators do not pose special problems: sloths blend in with the trees and, moving only slowly, do not attract attention. Only during their infrequent visits to ground level do they become vulnerable. The main predators of sloths are the jaguar, the harpy eagle, and humans. The majority of sloth deaths in Costa Rica are due to contact with...