A long time ago, people used to think bats were birds without feathers. But now we know that there is no such thing as a featherless bird. We know that bats are MAMMALS, just like people.
Some of the things that tell us bats are mammals:
But bats are very special mammals. They are the only mammals that can fly (without an airplane!) Flying squirrels are mammals too, but they don't really fly. They jump from high in a tree glide through the air like a kite. Bats flap their wings and fly like a bird.
Scientific Information: Bats make up the order Chiroptera.