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Amanda Maxwell

Feb 20th 2022

How Moth Cloaking That Outwits Bat Sonar Is Inspiring Stealth Technology

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Camouflage probably makes you think of dazzle ships or zebra stripes — visual hacks for invisibility to outwit potential predators. But there’s also the type of cloaking technology that stops more than visual detection. For example, moths have developed high-tech ways to confuse bat sonar, simply by using wing architecture as a stealth coating to absorb sound waves.

Moths are locked in an age-old struggle for survival; even under cover of darkness, it’s risky for them to fly at dusk and nighttime, as they’re still visible to their top predator, bats. Equipped with biosonar, bats use echolocation to send out high-pitched acoustic radar to bounce back from potential meals in flight. Bat sonar helps them locate and identify moths for dinner on the move.

But as recent research shows, moths are far from defenseless: Cloaking technology in the moth armory includes jamming signals, distraction and silencing.

It’s All About the Wing

Moth wings are covered in overlapping layers of tiny scales. They’re not just there for decoration, though; some patterns act as visual camouflage to blend into surroundings or mimic a bigger, tougher predator.

A recent study published in the Proceedings of the National Academy of Sciences (PNAS) used a method called acoustic topography to show that the repeating patterns of scales on the moth wings give an important advantage to moths in flight. The research team used empirical and mathematical analysis to show that earless moth species possess sound-absorbent wings.

Projecting sound waves at the wings, a team of researchers discovered the echoes bouncing were much quieter, as New Scientist describes. In other words, when the bat sonar hits the moth wings, the echo coming back to the bat is much fainter and harder to detect — and it doesn’t translate as a meal, either.

Another PNAS paper in 2018 used laser Doppler vibrometry and 3D modeling to show that the way the moth wing scales are arranged covers the whole bat echolocation range. According to Science News, the wings absorb around 50% of the bat sonar energy hitting the wing. Quieter echoes and low signal volume translate as not worth hunting to the bat, and the result is one safe moth.

Moth Ears: Jamming Signals and Redirection

Another way to evade capture is to listen for trouble. Some moth species have developed “ears” capable of detecting bat sonar. PBS Nova describes that, when they hear the echolocation pings, the moths simply swerve to avoid being caught. Some moths will also loudly announce how toxic they are.

Jamming bat echolocation with a burst of ultrasound also helps. A 2015 PNAS research paper showed that moths would send out jamming signals in response to playback of bat squeaks in the lab. According to Nature, some species manage this by rubbing their genitals against their abdomens.

Lunar moths use their long, twisty tails to throw bats off the chase. University of Washington researchers found that both the length and the twist were essential in distorting the echolocation signals, pushing the echo center away from the vulnerable body area. Bats were confused by the return signal and often chased after a moth that wasn’t where they thought it was.

Biomimicry for Aircraft Stealth

Commenting on the recent PNAS paper in New Scientist, researchers compare the moth acoustic camouflage to the cloaking technology used to keep stealth bombers hidden from enemy radar.

Stealth technology, also known as low observable technology, is a key tool in military applications that renders personnel and equipment invisible to radar, infrared, visual and other observation spectra. Altering the shape of an aircraft wing or fuselage, for instance, or applying a special coating can distort reflection or absorb the electromagnetic radiation from radar, similar to the way that the scales on the moth wing provide acoustic camouflage.

Biomimicry, or copying examples of how nature solves a visibility issue, often inspires new stealth technology. Maybe one day, moth scales could be deflecting more than just bat sonar.

Are you interested in all things related to technology? We are, too. Check out Northrop Grumman career opportunities to see how you can participate in this fascinating time of discovery.

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