The short version
- When a bat closes in, many male hawkmoths answer with bursts of ultrasound made by scraping special scales near the tip of the abdomen.
- A Florida Museum-led team found three different scraping mechanisms and estimates the defence evolved independently at least four and possibly seven times over about 30 million years.
- Whether the sounds jam the bat’s sonar, startle it or warn it off is still not settled, and females were not studied.
A hawkmoth cannot outfly a bat, so some of them talk back. When a bat attacks, males of many species rub specialized scales on their genital structures against a patch of their abdomen and give off bursts of ultrasound. A study published November 4 in Proceedings of the Royal Society B, led by Paul Masonick and Akito Kawahara of the Florida Museum of Natural History with Jesse Barber of the American Museum of Natural History, maps where that ability came from. The team played recordings of attacking bats to live moths, recorded what they made, and imaged the sound-making parts with electron microscopy and micro-CT.
They found three systems: scales scraped against other scales, against stiff spines, or against tiny bumps that had not been described before. According to Science News, 77 of the 143 species tested made ultrasound, and the ability arose independently at least four and possibly seven times between about 5 and 30 million years ago. Phys.org reports that 124 species were examined anatomically and 310 placed on the family tree. Species with ears tended to make the sounds best suited to interfering with sonar. “It goes to show how intense bat predation is on insects,” Masonick told Science News. Bats have tricks of their own; we covered how bent-winged bats shift their pitch to avoid jamming each other.
Continuous scraping may jam sonar and irregular bursts may startle or mimic bad-tasting prey, but which effect each sound has on bats has not been tested, and females were left out.
