Question

what would be the only flying mammal

Answer 1

Bats are the only mammals capable of flying.
They exhibit true and sustained flight.

Answer 2

Did you know that there is only one mammal in the world that can fly? Many people think that flying squirrels, flying possums and colugos (flying lemurs, which actually aren't even lemurs) can fly. But, the can't. They can only glide for limited distances. The only mammal that is actually capable of powered flight is the bat.