Most of a bat’s wing is hand. The name of the mammal group that includes bats, its Order, is Chiroptera which literally means hand wing. The finger bones are much longer in proportion than ours, especially compared to the forearm, elbow and upper arm bones. A thin, double membrane of skin connects the long fingers with the rest of the arm and the bat’s body to create the flying surface.
This creates a wing that is extremely flexible in how it attacks the air. Most bats are extremely maneuverable because of that. Tiny hairs across the whole wing are tiny sensors to help the bat “know” how it is going through the air (the visible hairs on the red bat wing above are for warmth and protection).
They use their thumb to help them climb and move around when not flying. Some bats can move around extremely well on “all fours”, their feet and thumbs. It is surprising, too, how fast most bats can climb with their feet and thumbs.
The bat’s wing muscles are very different than the wing muscles of a bird. A bird’s wing muscles are mainly across the chest, whereas the bat’s wing muscles are fairly equal across the chest and back.
Bats fly with a swimming motion through the air. Think of an Olympic swimmer, like Michael Phelps, doing the butterfly stroke. Like swimming, flying is energy demanding. When in flight, a bat’s heartbeat can reach 900-1000 beats a minute (compared to 400 beats a minute when resting and 20 beats a minute when in torpor).
Bat wings come in varied sizes and shapes, which affect how the bat can fly. Some wings are sleek and narrow, called high-aspect ratio wings, just like on a jet. Like a jet, bats with these wings are fast fliers.
At the other end of the spectrum are wings that are short and round, called low-aspect ration wings, just like on a stunt biplane. And like that biplane, bats with these wings fly slow, but are extremely maneuverable. Different bat species will have a whole range of wing shapes in between, too.