Luna moths foil bat sonar with their spinning tails.
Bats are well known as stealthy hunters that use echolocation to navigate the night skies and find tasty insect prey along the way. A team of scientists has recently discovered a novel acoustic weapon that some moths use to avoid becoming the next late-night bat snack. Luna moths, and their relatives in the Saturniid family of Lepidoptera, sport long hindwing tails that spin at high frequency to distract their bat foe in mid-strike. High-speed infrared video and advanced audio techniques were used to capture the amazing action of the bat-deflecting calls produced by rapidly whirling moth tails. Authors of the new study  speculate that tail interference lures the encroaching bat away from a lethal strike to the moth’s body core. Instead, the bat hits non-essential edges, or misses its intended prey entirely. In fact, spinning luna moth tail action diverted lethal bat attacks nearly half the time. That’s a pretty big anti-bat advantage!
VIDEO: Big brown bats (E. fuscus) aiming at the tails of luna moths (A. luna). The movie is slowed down ∼6 times. [From Barber et al., PNAS March 2015]
Is all this tail spinning just a coincidence? To answer this question, researchers designed a series of experiments that proved Saturniid hindwing tails are not important for flight or other routine moth activities. Bat distraction appears to be their primary function, suggesting natural selection has favored inheritance of these life-saving appendages.
Co-evolution of predator/prey relationships is often compared to an arms race. Adaptations that give advantage to the predator tend to be balanced over time by adaptations in prey that thwart them. Interestingly, brown bats in the laboratory did not learn to ignore the distracting luna moth sounds, or adjust their own echo patterns to compensate. This suggests that bats don’t have a good counter defense, at least for now.
Many animals rely on visual tricks such as camouflage (blending in) or mimicry (looking like something else) to escape their predators. Those visual strategies don’t work against bats since they have very poor eyesight and rely instead on sound. Biologists have studied some equally fascinating anti-bat acoustics in other moth families. For example, tiger moths have special bat-detecting ears and may emit high-frequency clicks that jam bat sonar . Scientists speculate that bats and moths have been engaged in various kinds of acoustic warfare for over sixty million years.
- Adaptation: change in an organism’s structure or behavior selected over time based on reproductive advantage
- Co-evolution: natural selection of adaptations in one species triggered by interactions with related adaptations of another species; often seen with predator and prey
- Echolocation: technique similar to sonar used by bats to navigate based on reflected echoes of their high pitched cries
- Lepidoptera: an order of insects that includes moths and butterflies
READ MORE: Check out these articles to learn about the evolutionary arms race between bats and moths.
- Moth tails divert bat attack: Evolution of acoustic deflection. Barber, J. et al., Proceedings of the National Academy of Science, March 2015. http://www.pnas.org/content/112/9/2812.short
- Moths Jam Bat Sonar, Throw the Predators Off Course. Kaplan, M., National Geographic News, July 2009. http://news.nationalgeographic.com/news/2009/07/090717-moths-jam-bat-sonar.html