What is the world's slowest animal?

A three-toed sloth with its baby on a branch.

Fast animals get plenty of attention for their incredible feats of speed. But what about animals that move at a slower pace?

"We definitely are programmed to think that speed is good," said James Maclaine, senior curator of fish at the Natural History Museum in London. "For a lot of animals, that doesn't make any sense to them at all."