Sloths are very slow-moving animals from the tropical forests of the Americas. They have the strange characteristic of changing colour according to the climate. In warm, dry weather, their coat is a brown colour. When it rains, the coat becomes greener, like the grass. This happens because tiny algae live in a sloth's fur which, in humid conditions, grow and turn the animal's coat green. Dozens of species of insects also live in fur without disturbing their host in the least. The sloth simply sleeps on, for hours and hours.