Sloths move only when necessary and even then very slowly: they have about a quarter as much muscle tissue as other animals of similar weight. They can move at a marginally higher speed if they are in immediate danger from a predator (4.5 m or 15 feet per minute), but they burn large amounts of energy doing so.
Sloth
The living sloths comprise six species of medium-sized mammals belonging to the families Megalonychidae and Bradypodidae, part of the order Pilosa. They are arboreal residents of the rainforests of Central and South America. The sloth's taxonomic suborder is Folivora, while some call it Phyllophaga. Both names mean "leaf-eaters"; the first is derived from Latin, the second from ancient Greek. Names for the animals used by tribes in Ecuador include Ritto, Rit and Ridette, mostly forms of the word "sleep", "eat" and "dirty" from Tagaeri tribe of Huaorani.