Many moths sport luxurious pelts of scales, making them look like fuzzy butterflies. Thomas Neil and his colleagues at the University of Bristol, UK, wondered whether this fuzz functions as acoustic camouflage, concealing the moths from echolocating bats.

To find out, the team designed a loudspeaker and microphone system that simulated the echolocation apparatus used by nocturnal bats to detect prey. The researchers first beamed echolocation signals at specimens of two species of moth. They then used tweezers and a stiff paintbrush to de-fuzz the specimens, which were again pelted with sounds. The scientists found that moth fuzz absorbs, on average, 67% of incoming sound energy — a much better performance than commercially available sound insulation of similar structure and thickness.

Both moth scales and manufactured sound absorbers consist of parallel fibres with air trapped between them. Sound waves enter these air pockets and bounce around, causing the air molecules to vibrate and dissipate energy rather than bouncing back to the source.

Thanks to this acoustic camouflage, a bat must be 9–18% closer to moths to detect them than it would if the moths were smooth.