From Agence France Press:
Feb. 29, 2008 — Nectar-sipping bats use the same aerodynamic trick that bugs use to hover in place, a study in the journal Science has found.
Swedish researchers set up honey water feeding stations in a massive wind tunnel and used fog, lasers and high speed cameras to track exactly how the bats flew.
They found that when the bats flapped their wings downward they created tiny air cyclones above the wings called a leading vortex which pulls the animal upward and allows them to hover in place without expending nearly as much energy as simply flapping their wings.
Without this trick they would not have the strength to hover in place in order to feed as the vortex provides as much as 40 percent of the lift force which keeps the bats in the air.
The bats used the thumbs and fingers embedded in the skin membrane of their flexible wings much like flaps on an airplane to alter the curve of the wing and create the lift force necessary to hover.
“To be able to generate these vortexes they need this exquisite control of their wing surface and it’s a really delicate thing to control the stability of this vortex,” said lead author Anders Hedenstrom of Lund University.
Posted in Nature, red in tooth and claw
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