How Long Wings Help Huge Moths Evade Bat Attacks
Scientists have determined that the longer a moth’s hind wings and tails are, the better chances the insects have of surviving a bat attack.
When an African moon moth unfurls its great, green wings, it becomes nearly as large as a ping-pong paddle. The creatures are gorgeous to behold, and with a juicy, nutrient-dense body sandwiched between gigantic wings, they’re a prized treat for a hungry bat.
What’s more, the moths’ hind wings sport a pair of long, dangly tails that look like they’d be perfect for snatching.
Yet even when bats use their superpower-like echolocation to zero in on the moths, the flying mammals miss more often than not. What gives?
According to a study published Wednesday in the journal Science Advances, the moon moths’ tails aren’t a liability—they’re an asset for deflecting the sound waves bats use to echolocate, or find prey. (See photos of some the world's most amazing—and misunderstood—moths.)
“It would seem that the bats are treating these moths with tails as though there are two targets that they can aim at,” says Juliette Rubin, a sensory ecologist at Boise State University’s Barber Lab and a lead author of the new study.
The best part? Both of these targets aim the bats away from the moth’s vulnerable center.
To understand how this works, Rubin and her coauthors pitted big brown bats against various species of moths with differently sized and shaped tails, some of which they artificially shortened or elongated for the purposes of the study. And the team discovered a fascinating trend.
“As hind wing length and tails get longer, moths increasingly escape their bat predators,” says Rubin, who is also a National Geographic Society grantee.
Die Another Day
A few extra inches of tail might not seem like much of a boon, especially considering some of the other anti-bat adaptations out there. Greater wax moths, for instance, have evolved highly sensitive hearing that can detect the shrieks of a bat as it approaches. And the hawk moths of Borneo can produce ultrasound by vibrating their genitals, effectively jamming the radar of their bat enemies. (Related: “Moths Vibrate Their Genitals to Avoid Bats.”)
But the benefits of the sensory illusion that a moth’s tails create can literally mean the difference between life and death.
With their tails intact, the green giants were able to survive a whopping 73 percent of bat attacks. But when Rubin and her coauthors cut off part of the African moon moths’ tails, the critters were able to escape only around 45 percent of the time. And if the tails were removed completely, the escape rate dropped to 34 percent, even though the moths’ ability to fly appeared to be unimpaired.
Interestingly, tails don’t seem to make the moths invisible to bats. Instead, the tails just scramble the bat’s perception enough to make it strike slightly off center, usually directing a hit at the hind-wings or the tails themselves.
“It’s actually quite rare that bats are gripping the tails and ripping them,” says Rubin, “but even if they do that, it seems like the moths are still able to get away quite successfully.”
Remember, says Rubin, “these are some very impressively sized moths.”
Building A Better Moth
In addition to filming moth and bat battles, the new study also created a detailed family tree, called a phylogeny, for all of the known species of silk moth. This revealed that anti-bat tails have evolved separately multiple times in this moth family, rather than all stemming from a common ancestor. This suggests that bats may be pushing moths toward forms with elongated or intricately cupped tails through natural selection.
“What surprises me most is that there appear to be many different ways to trick a bat's echolocation system, and that a variety of moths appear to have converged on these strategies independently,” says Aaron Corcoran, an organismal biologist who studies bat echolocation at Wake Forest University.
Corcoran also points out another detail from the study—the bats never got better at hunting the long-tailed moths, despite several months of hunting them night after night.
“Scientists have spent decades revealing just how good bats are at perceiving the world with echolocation,” he says. “The fact that the bats in the study never learned how to catch these moths, despite ample time to do so, shows how hard-wired this blind spot is in the bat's perception.”
Of course, this doesn’t mean moths have all of a sudden won the evolutionary arms race.
The moths may have found a fool-proof way to trick bats’ sonar, but given enough time, the bats could evolve to rely less on sonar and more on vision. In which case, the moths’ longer, more intricate tails could hypothetically shift from advantage to liability.
That’s the beauty, and the terror, of evolution. Just when you think you’ve won the game, the rules change. And then you’re dinner.
Related Topics
You May Also Like
Go Further
Animals
- Octopuses have a lot of secrets. Can you guess 8 of them?
- Animals
- Feature
Octopuses have a lot of secrets. Can you guess 8 of them? - This biologist and her rescue dog help protect bears in the AndesThis biologist and her rescue dog help protect bears in the Andes
- An octopus invited this writer into her tank—and her secret worldAn octopus invited this writer into her tank—and her secret world
- Peace-loving bonobos are more aggressive than we thoughtPeace-loving bonobos are more aggressive than we thought
Environment
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
- Food systems: supporting the triangle of food security, Video Story
- Paid Content
Food systems: supporting the triangle of food security - Will we ever solve the mystery of the Mima mounds?Will we ever solve the mystery of the Mima mounds?
History & Culture
- Strange clues in a Maya temple reveal a fiery political dramaStrange clues in a Maya temple reveal a fiery political drama
- How technology is revealing secrets in these ancient scrollsHow technology is revealing secrets in these ancient scrolls
- Pilgrimages aren’t just spiritual anymore. They’re a workout.Pilgrimages aren’t just spiritual anymore. They’re a workout.
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- This ancient cure was just revived in a lab. Does it work?This ancient cure was just revived in a lab. Does it work?
Science
- The unexpected health benefits of Ozempic and MounjaroThe unexpected health benefits of Ozempic and Mounjaro
- Do you have an inner monologue? Here’s what it reveals about you.Do you have an inner monologue? Here’s what it reveals about you.
- Jupiter’s volcanic moon Io has been erupting for billions of yearsJupiter’s volcanic moon Io has been erupting for billions of years
- This 80-foot-long sea monster was the killer whale of its timeThis 80-foot-long sea monster was the killer whale of its time
Travel
- How to plan an epic summer trip to a national parkHow to plan an epic summer trip to a national park
- This town is the Alps' first European Capital of CultureThis town is the Alps' first European Capital of Culture
- This royal city lies in the shadow of Kuala LumpurThis royal city lies in the shadow of Kuala Lumpur
- This author tells the story of crypto-trading Mongolian nomadsThis author tells the story of crypto-trading Mongolian nomads