The sloth's scientific name, Bradypus, is Greek for "slow feet", which seems fitting since they are the world's slowest animal. Sloths are so slow that algae actually grow on their fur! The algae is actually a good thing for the sloth, as it helps them blend into the trees.
Sloths can only climb 6 to 8 feet per minute, which is very slow compared to most mammals. Sloths however, are excellent swimmers. Sloths will drop themselves off branches in order to get to the rivers for a swim.
Since sloths bodies are only made up of 25 percent muscle, they can't shiver when they are cold to warm up. This is why they are found in tropical climates and are covered in fur. There are times of cold in the forest, though. If a female gets too cold, she is unable to digest food. If her young is still nursing, she may starve to death.
A sloth only has its claws for defense against predators. However, its very low level of movement and the camouflage make it difficult to notice.
Source: Live Science