What is the only mammal capable of true, flapping flight?

Flying squirrels, sugar gliders and colugos all have a stretchy flap of furry skin between their limbs. They launch from a high branch and glide down — but they can’t flap to climb back up. That makes them gliders, not fliers.

Bats are different. They beat their wings to create lift, so they can take off, climb, hover and turn on a dime. That’s powered flight, and among mammals only bats can do it.