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How Bats Fine Tune their Flight
Jun 18, 2014

Researchers have said that a new study of bats reveals a capability within their wondrous wings that may help them fine-tune their flight. 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. 

Birds and insects have stiff wings, but the new evidence suggests bats have evolved this muscular means of preserving or adjusting wing shape. The aerodynamic performance depends upon wing shape, the shape of a membrane wing might initially begin flat but as soon as it starts producing lift it's not going to remain flat because it has to deform in response to that aerodynamic load.


The shape it adopts could be a terrible one—it could make the animal crash—or it could be beneficial, but they are not locked into that shape. 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.


For this study electrode sensors were attached to a few muscles on the wings of a few Jamaican fruit bats and filmed them as they flew in the lab's wind tunnel. Three key findings emerged from the data. They all point to the plagiopatagiales modulating skin stiffness.

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

  • Wing surface changes during flight area of detail shows plagiopatagiales, tiny muscles that work together to stiffen or reshape an area of the bat's wing during the wingbeat cycle.

  • Another finding was that the muscles don't act individually. Instead they exert their force in synchrony, providing enough collective strength to stiffen the wing.


Finally, the muscles appeared to activate with different timing at different flight speeds. As the bats flew faster, they tensed the muscles sooner in the up-stroke-down-stroke cycle.




 

 


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