Sloths are classified as folivores, as the bulk of their diets consist 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 diets. 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 nutrients, and do not digest easily. Sloths, therefore, have large, specialized, slow-acting stomachs with multiple compartments in which symbiotic bacteria break down the tough leaves. Sloths have the unique ability to protrude their tongues from their mouths 10 to 12 inches (25 to 30 cm), an ability that is useful for collecting leaves just out of reach. 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.
Since leaves provide little energy, 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 (30–34 °C or 86–93 °F), and still lower temperatures when resting.