Research has revealed how moths evolved defensive mechanisms to protect themselves against their sonar-equipped predators.

Video: Bat duped by moth's tail caught on video

For 60 million years, bats and moths have been at war, competing against one another in nocturnal duels.

At first glance it might appear to be a mismatch. Not only do they have a significant size advantage, but bats also have sonar allowing them to navigate in the dark.

But research has discovered how bat attacks have driven Madagascan silk moths to evolve a built-in bat decoy.

They have developed hindwings with long, elaborate "tails" that deflect bats' sonar by creating a misleading target for them to aim at.

When bats swoop in for the kill, they often miss the moths' bodies and strike the expendable tails.

Co-author Dr Akito Kawahara and his team mapped the evolution of hindwing shape in silk moths through a detailed family tree.

Male Madagascan moon moth (Argema mittrei) caught at Centre ValBio in Ranomafana, Madagascar. This species is from the same genus as the moon moths used in this study. Credit: The Barber Lab at Boise State University
Image: A male Madagascan moon moth's long tail was evolved to thwart bat attacks. Pic: Barber Lab/BSU

They discovered that the evolution of hindwing length and complexity was not gradual, but involved abrupt and sudden shifts.

This suggested that certain wing shapes were significantly more effective at deflecting bats than others.

Four classes of shapes were linked with moths' ability to escape their predators, and nearly identical shapes were consistently evolving among unrelated moths.

"We see moths moving toward peaks of optimal shapes with unrelated moths evolving in similar ways," Dr Kawahara said. "This speaks to bats' selective pressure on their prey."

Dr Juliette Rubin, the study's lead author, suggested that this defensive strategy might be a coup for silk moths.

"Prey might evolve in ways that exploit weaknesses in the armour of their predators' perception," Rubin said. "We think this is happening across different systems, not just in moths."

What is unclear in one of nature's longest-running wars is whether bats can now evolve again to get round the decoy - but so far they have not been able to learn how to tell the difference between a moth's body and its decoy tail.

"If these tail traits are altering or manipulating the information bats are receiving as they try to assess where the moth is and where to attack, that could be a hard strategy for bats to get around," said Dr Rubin.

The study, published in Science Advances, was conducted by scientists at the University of Florida and Boise State University.