New research has found that deaf moths can hide from the ultrasonic radar of bats to prevent themselves from becoming dinner. Since the moths are unable to hear and take evasive action against the bat’s ultrasonic calls, they have evolved an "invisibility cloak" of noise-canceling scales, preventing the bats from knowing their position.
The dynamics of bat-moth interactions are a stunning example of adaptive prey and predator responses. Bats, who have poor vision at night, use a series of ultrasonic echolocation calls to track and catch their food. By sending out high-frequency calls they can navigate their environment by detecting how the sounds are reflected as they hit various objects. This audible map builds a picture of the bat’s surroundings, using frequencies pitched at around 20-100 kilohertz, which is inaudible to the human ear.
Some moths have evolved to thwart this hunting technique by “talking back” and jamming the bat’s ultrasonic radar, an adaptive technique that has been observed in tiger moths. Other moths that are toxic to bats appear to have developed ultrasonic warnings that they emit when hunting bats are in close range. A juvenile bat may still nibble on a few toxic moths before it puts two and two together, but researchers found moths with the sound apparatus removed were hunted readily while those emitting warning noises were avoided. In this video you can see the bat’s “nope” in action, as it clocks last minute that this snack will only end in tears. Both of these responses, however, rely on the moth knowing the bat is coming, which isn’t so easy if you can’t hear anything. So, what is a deaf moth to do?
A team of researchers at the School of Biological Sciences in Bristol examined external characteristics of two species of deaf moth, Antherina suraka and Callosamia promethea. They observed that the thorax scales look structurally similar to materials used for noise insulation and wondered if this constituted some form of acoustic camouflage, publishing their findings in the Journal of the Royal Society Interface.
Using scanning electron microscopy, they looked at what happened when sound energy similar to that of a predatory bat call was directed at the moths and found the scales on their bodies were capable of absorbing up to 85 percent of the sound. In the wild this could hamper a bat’s ability to detect the presence of a moth by almost a quarter, meaning the deaf moths could evade predation without so much as lifting a wingtip.
"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 lead author Dr Thomas Neil, Research Associate from Bristol's School of Biological Sciences, in a statement. "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."
So, who knows? If you’ve got an aspiring drummer in the flat next door making your life a living hell, moth wallpaper could be the answer.
Ever wondered what a bat can "see" when using its ultrasonic radar? This "bat ear" can show you.