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8:52 p.m. // 2008-10-01

The living sloths comprise six species of medium-sized mammals that live in Central and South America belonging to the families Megalonychidae and Bradypodidae, part of the order Pilosa. Most scientists call the sloth suborder Folivora, while some call it Phyllophaga. Both names mean "leaf-eaters"; the first is derived from Latin, the second from ancient Greek. Tribal names include Ritto, Rit and Ridette, mostly forms of the word "sleep", "eat" and "dirty" from Tagaeri tribe of Huaorani.

This article mainly deals with the living tree-dwelling sloths. Until geologically recent times, large ground sloths such as Megatherium[2] lived in South America and parts of North America, but along with many other animals they disappeared immediately after the arrival of humans on the continent.[citation needed] Much evidence suggests that human hunting contributed to the extinction of the American megafauna, like that of far northern Asia, Australia, New Zealand, and Madagascar. Simultaneous climate change that came with the end of the last Ice age may have also played a role in some cases. However, the fact that ground sloths survived on the Antilles long after they had died out on the mainland points towards human activities as the agency of extinction.

The living sloths are omnivores. They may eat insects, small lizards, and carrion, but their diet consists mostly of buds, tender shoots, and leaves, mainly of Cecropia trees. 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 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 creature of their size), and maintain low body temperatures when active (30 to 34 �C or 86 to 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.[citation needed] 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.

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