How bats fine-tune flight with tiny muscles

Bats are the only mammals to have developed the capacity to fly and to find their prey. They can maneuvre flight in difficult environment in ways that birds cannot.

Researchers have now discovered that the synchronised acts of their tiny muscles can help bats fine tune their flight.

Birds and insects have stiff wings, but bats employ a network of nearly hair-thin muscles embedded in the membrane of their inherently floppy wing skin to adjust the wings' stiffness and curvature while they fly, the study said.

"Because bats have these muscles in their wings, and also bones that can control the general shape as well, they can adopt any number of profiles," said Jorn Cheney of Brown University in the US.

The researchers attached electrode sensors to a few tiny muscles called plagiopatagiales on the wings of a few Jamaican fruit bats and filmed them as they flew in the lab's wind tunnel.

The results showed that the plagiopatagiales modulated skin stiffness.

One result was that the muscle activation and relaxation follows a distinct pattern during flight: They tense on the downstroke and relax on the upstroke.

"This is the first study showing that bats turn these muscles on and off during a typical wingbeat cycle," said Sharon Swartz, a professor of biology at Brown University.

The study appeared in the journal Bioinspiration and Biomimetics.