Moths use ultrasound to defend against bats
Using artificial intelligence, researchers have discovered what may be the largest animal mimicry complex on Earth, changing the way we see, or rather hear, the night sky. Credit: Chandan Singh, CC BY 2.0
While a clear night sky may seem calm and peaceful to us, empty of everything but stars, this nocturnal world is filled with a cacophony of high-pitched sounds beyond our ability to hear. Bats penetrate shadows with ultrasonic pulses that allow them to create an auditory map of their surroundings, which is bad news for moths, one of their favorite foods.
However, not all moths are defenseless prey. Some emit their own ultrasonic signals that startle the bats to stop the pursuit. Many moths that contain bitter venom avoid capture altogether by producing a different ultrasound that alerts the bat to its foul taste. Others hide themselves in a static sonar-jamming shroud that makes them difficult to locate with bat echolocation.
Although effective, this type of auditory defense mechanism in moths is considered relatively rare, known only in the tiger moth, eagle moth, and one species of geometric moth. But a new study published in Proceedings of the National Academy of Sciences showed that ultrasound-producing moths were much wider than previously thought, adding three newly discovered sound-producing organs, eight new subfamilies and potentially thousands of species to the list.
“It’s not just tiger moths and eagle moths that do this. There are many moths that make ultrasonic sounds, and we know almost nothing about them,” said senior author Akito Kawahara, curator at the McGuire Center of the Florida Museum of Natural History. for Lepidoptera & Biodiversity.
The researchers are also interested in understanding how these sounds may converge between moth species. In the same way that non-venomous butterflies mimic the colors and patterns of the wings of less savory species, moths that have no innate venom benefit can mimic the tones and pitches of a relative’s voice that are completely unappetizing.
After collecting and studying thousands of moths over more than a decade in Ecuador, French Guiana, Mozambique and Malaysian Borneo, the researchers spent the last two weeks in Ecuador, where they recorded alarm calls from every moth they could catch. After that, they analyzed these recordings with the help of theoretical physicists and machine learning algorithms that examined each note, looking for similarities.
The program revealed what, until now, only other researchers could guess: Moth species don’t act like individual composers, each with a unique calling card and distinct style. Instead, a small number of moths obtained their own scores, which appeared to be replicated by other moths in complex acoustic mimicry rings.
Lead author Jesse Barber, a professor of biology at Boise State University, said more work was needed to uncover the exact nature of these sounds, but he suspected the pioneer moths in the center of the ring might be dangerous, while the imitators on the periphery were dangerous. just fake advertisers.
“Moths and butterflies collectively are one of the most diverse groups on the planet, containing one in every 10 animals mentioned. If these results are successful, it will likely be the largest collection of mimicry complexes on Earth,” he said.
This ultrasonic warning system seems so useful for avoiding bats that they have evolved independently in moths on several separate occasions. In each case, the moths turn their different body parts into finely tuned organic instruments.
“Tiger moths have a structure called a tymbal, which bends inward and outward,” Kawahara said. “Some of them use structures on their wings, some use their stomachs, while others use modified genitals.”
Several different types of clicker and scraper moths used as bat repellents are described in this study for the first time. This includes a species of calpine moth that rubs against overlapping belly scales, similar to the way crickets make their characteristic chirping sound. Another species, in a group called the snout moth, makes sound by using a structure resembling a guitar pick between its wings, which is swiped when the moth is flying.
The anti-bat signal isn’t just limited to moths. Some tiger beetles can make a defensive click on a bat by flapping its wings against its protective sheath. Other groups of insects, such as katydids, crickets and mantids can hear incoming bats, and Barber notes the possibility that some may have an as yet unknown ability to communicate with their pursuers. But with about 40% of insect species currently at risk of extinction, at a rate that is beyond the ability of researchers to find and name them, he warns of the very real possibility that this ultrasonic symphony may fall silent before we have a chance. to hear or learn its meaning.
“This mimicry complex is likely not confined to moths,” he said. “A whole tapestry of nocturnal insect life may be involved, but the opportunity to understand the natural world will be lost. So many lineages have become extinct that it is likely that we are in the last golden age of biology. We could still understand how life unfolded, if we did it now.”
Infrared camera shows moths come in a variety of colors
Jesse R. Barber et al, Production of anti-bat ultrasound in moths is widespread globally and phylogenetically, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2117485119
Provided by the University of Florida
Quote: Moths using ultrasound to defend against bats (2022, 22 July) retrieved 23 July 2022 from https://phys.org/news/2022-07-moths-ultrasound-defend.html
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