While many insects that would otherwise become bat food rely on the sounds created by the nocturnal creatures to dodge their advances, deaf species of moth have no such luxury. These critters do have another trick up their sleeve, it turns out, with researchers discovering special scales on their bodies that evolved to absorb the sounds instead, serving as a type of acoustic camouflage to throw hungry bats off the scent.

Bats zero in on their prey by emitting sound waves and analyzing the returning echoes, using this type of biological sonar to track down dinner and find their way around. Many insects have developed an ear for these sounds, recognizing them as a prompt to seek shelter, but deaf moths are obviously oblivious to these warning signs. This led researchers at the University of Bristol to wonder what evasive methods they may be using instead.

The team used an imaging technique called scanning electron microscopy to observe the thorax scales on the bodies of four deaf moth species in fine detail. In doing so, they noticed that they closely resembled the structures of fibers used in sound insulation materials, indicating that some kind of noise-cancelling trickery could be at play.

Through follow-up experiments, the team found that these scales can absorb as much as 85 percent of incoming sound energy. Applied to the animal kingdom, this would make it much harder for a bat to find these types of moths, with the team calculating that the scales reduce the distance from which a bat would be able detect them by almost 25 percent.

This kind of naturally evolved "acoustic camouflage," as the researchers call it, could offer lessons when it comes to manmade sound insulation systems.

“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,” said Dr Thomas Neil, lead author of the study. ”We are now looking at ways in which we can use these biological systems to inspire new solutions to sound insulating technology and analyze the scaling on a moth's wing to explore whether they too have sound absorbing properties."

The research was published in the journal Royal Society Interface.

Source: University of Bristol