As bats cruise the night skies looking for insect prey, one species of moth has developed an intriguing defense strategy, using its long wing tip "tails" to fool attacking bats into missing their target - the moth's body.
This diversionary tactic was discovered by researchers at Boise State University using high-speed cameras to watch bats using echolocation to hunt one type of prey, the luna moth, renowned for the long trailing tails on its wings.
The researchers found that as the moths fly, those tails spin, creating a sonic signal that can garble the echo returning to the bats, leading them to attack the expendable tails and miss the moths' vulnerable bodies.
Distracting a predator in an attempt to get it to attack a non-essential part of the body is common in nature, but most techniques are visual -- brightly colored spots on the wings of butterflies or the fins of fish to encourage predators to strike at the edges of the wings or fins, for example.
The luna moth's deception technique is more unusual in its use of sonic rather than visual cues, the researchers reported in the Proceedings of the National Academy of Sciences.
Luna moths can fly perfectly well if they lose those tails, studies have found, suggesting they evolved as a protection against predators rather than as an aerodynamic aid.
In an experiment, the Boise State scientists with research colleagues from the University of Florida and Northeast Ohio Medical University took 200 luna moths and clipped the wing tails off half of them.
They then introduced the moths into an enclosed area housing eight hungry brown bats, and recorded the result with high-speed cameras and ultrasonic microphones that could capture the bat's echolocation squeaks.
Luna moths allowed to keep their tails were 50 percent more likely to survive than those whose tails had been clipped, they found.
More than half the time, when bats went after the intact moths they did attack the wing tails.
Normally when bats attack, they use their wings and tail to scoop an insect's body towards their faces so they can deliver a killing bite.
The luna moth's auditory distraction, courtesy of their wing tails, proved highly effective, the researchers found, either causing the bats to miss the moths entirely or at best getting just a mouthful of wingtip while the moth escapes.
"Clearly, tails provide an anti-bat advantage," Barber says.
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