These Deaf Moths Defy Bats Using Stealthy Acoustic Camouflage

CC BY 2.0. Antherina suraka. Photo: Resenter89 / Flickr

Some moth species have evolved noise-cancelling abilities that are more efficient than today's sound engineering technology.

So bats are pretty remarkable, right? Around 65 million years ago, they came up with a plan to hunt at night using echolocation. Also known as biological sonar, bats emit really loud, really high-pitched noises that bounce back and let them know what's out there. It makes them excellent hunters in the dark.

Meanwhile, many nocturnal insects have created a workaround by evolving the ability to hear the ultrasonic calls of bats, allowing them to get out of Dodge before becoming dinner.

But what's a deaf and delicious moth to do? Researchers from the University of Bristol discovered the answer, and it's fascinating.

Using scanning electron microscopy, the team found that the thorax scales of earless moths Antherina suraka and Callosamia promethea looked structurally similar to fibers used as noise insulation. So they decided to investigate if these scales might be somehow absorbing the bat clicks and dampening the echoes returning to the bat, "offering the moths a type of acoustic camouflage."

And sure enough, they found that the moths have evolved the nifty trick of being able to absorb as much as 85 percent of the incoming sound energy from bats. The sound absorbing scales can reduce the distance a bat would be able to detect a moth by almost 25 percent, potentially "offering the moth a significant increase in its survival chances."

The team says that the scales are more efficient than today's sound engineering technology.

sakura moth
Antherina suraka. Resenter89 / Flickr/CC BY 2.0

"We were amazed to see that these extraordinary insects were able to achieve the same levels of sound absorption as commercially available technical sound absorbers, whilst at the same time being much thinner and lighter," says lead author Dr Thomas Neil, Research Associate from Bristol's School of Biological Sciences.

The discovery may inspire new solutions to sound insulating technology; once again, revealing the remarkable design skills of Mother Nature, and how the relationships between organisms lead to such wondrous adaptations.

"Moths and bats are considered a classic example of a predator–prey evolutionary arms race," write the authors. For now, it appears that these moths have the edge – but only time will tell. Your move, bats.

The paper, "Thoracic scales of moths as a stealth coating against bat biosonar," was published in Royal Society Interface.