The three-toed sloth's lethargic life revolves around sleeping and eating, and most energy is expended descending trees to go to the toilet. Often described as having a body built to hang, they look like bundles of leaves, partly owing to their silent stillness and partly because their fur contains a camouflaging algae. Of the four species, which are found hanging around in the rainforests of South America, one - the critically endangered pygmy three-toed sloth - is found only on a tiny five square kilometre island off the coast of Panama.

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