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Bats use same flying trick as insects

Bats stay aloft by employing an aerodynamic trick previously thought unique to insects, researchers said on Thursday.
Embargoed: Not for Release Until 2:00 pm US ET, 28 February 2008    TO GO WITH AFP STORY-SCIENCE-US-SWEDEN-ANIMALS-BATS by Mira Oberman This handout photo received on February 28,2008 courtesy of Science/F.T. Muijres,Lund University shows a Pallas' long-toungued bat in flight. Nectar-sipping bats use the same aerodynamic trick that bugs use to hover in place, a study released on February 28, 2008 by 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. AFP PHOTO/SCIENCE/F.T. Muijres,Lund University //HANDOUT= RESTRICTED TO EDITORIAL USE =GETTY OUT= (Photo credit should read F.T. MUIJRES/AFP/Getty Images)
Embargoed: Not for Release Until 2:00 pm US ET, 28 February 2008 TO GO WITH AFP STORY-SCIENCE-US-SWEDEN-ANIMALS-BATS by Mira Oberman This handout photo received on February 28,2008 courtesy of Science/F.T. Muijres,Lund University shows a Pallas' long-toungued bat in flight. Nectar-sipping bats use the same aerodynamic trick that bugs use to hover in place, a study released on February 28, 2008 by 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. AFP PHOTO/SCIENCE/F.T. Muijres,Lund University //HANDOUT= RESTRICTED TO EDITORIAL USE =GETTY OUT= (Photo credit should read F.T. MUIJRES/AFP/Getty Images)F.t. Muijres / AFP - Getty Images
/ Source: Reuters

Bats stay aloft by employing an aerodynamic trick previously thought unique to insects, researchers said on Thursday.

Using a wind tunnel to study the wake bats leave as they fly, they found that a tiny cyclone of air over each wing called a leading edge vortex provided as much as 40 percent of the lift required to keep the animals in the air.

"It wasn't known that vertebrates can do it too," Anders Hedenstrom, a biologist at the University of Lund in Sweden who led the study, said in a telephone interview. "Now we have found bats have used a similar mechanism."

The shape of the wings of planes and birds produce lift by utilizing a more steady stream of air, Hedenstrom said. Bats take advantage of additional lift created in the downstroke of the wing that allows them to hover and fly more nimbly.

The researchers filled the wind tunnel with an aerosol fog to help capture images of the bats as they flew towards a tube of honey water, then analyzed the images on a computer.

When the bats hovered they created a vortex above each wing.

"This is the mechanism behind this high lift force during hovering flight," Hedenstrom said.

The findings, published in the journal Science, have practical implications. Engineers, for example, can use this knowledge when developing micro-air vehicles, Hedenstrom added.

Such robotic machines — with potential uses for surveillance — might be able to fly in and out of buildings and confined areas because their flapping wings would permit hairpin turns and hovering, he added.

"To really make them work this is an important piece of information, because it shows how we control the wing's structure during a wing stroke," Hedenstrom said. "With fixed wings they can't turn on a dime."