Your pet cat purrs, and so do some of her larger relatives, like the puma and the bobcat, as well as the cat-like animal called a genet, raccoons, badgers, tapirs, and even guinea pigs. Scientists aren't entirely sure how a cat purrs, but they do know that felines can either purr or roar, but not both (lions, for example, don't purr). They also suspect that a purr evolved as communication between mother cats and nursing kittens.