Spinning Tails: How These Moths Confuse Preying Bats

If you're a moth gracefully fluttering through a clear night sky, a bat is a lot like a giant flying monstrosity of claws, fangs, and leathery skin. And thanks to their nifty sonar, those monsters can zero in on you in seconds, even while a new moon cloaks you in the cover of darkness. That just hardly seems fair!

What moths really need is some way to keep bats confused despite that troublesome sonar. Now a new study has determined that one species of moth can do just that, ironically keeping those leather monsters off their tail by using their tails.

"This finding expands our knowledge of anti-predator deflection strategies and the extent of a long-standing evolutionary arms race between bats and moths," Akito Kawahara, assistant curator of Lepidoptera at the Florida Museum of Natural History, explained in a statement.

Kawahara recently led a team of researchers, in collaboration with the University of Florida and Boise State University, to determine how bats so frequently miss their fluttering prey, even when their sonar and agile means of flight should ensure accurate grabs.

Past studies have found that some of this inaccuracy can be blamed on competitive sonar jamming, where bats even from the same colony will disrupt one another's hunting efforts in an attempt to steal limited prey.

However, bats can even miss a moth target when alone, and researchers wanted to know why. Using high-speed infrared cameras and ultrasonic microphones, the researchers watched brown bats preying on moths, taking note of what prey was successfully snagged and under what circumstances did prey get away.

They found that luna moths with tails were 47 percent more likely to survive an attack than moths without tails. Bats targeted the tail during 55 percent of the interactions, suggesting the moths may lure their predators to the tails on purpose.

"When you pit them against bats, bats can't find the moths," Kawahara explained. "They go to the tail instead of the head," foiling an instant kill.

The researchers suspect that luna moths spin their trailing hindtails as they fly to confuse bats' sonar cries. Exceptionally long and delicate, these tails are also not completely necessary for luna flight, strengthening the argument that they are indeed decoys.

The results were published in the journal Proceedings of the Natural Academy of Sciences.

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