Wake Forest researchers study moth mimicryTasty ones fake out bats by copying sounds of their toxic cousins

By Laura GiovanelliJOURNAL REPORTER

We've all pretended we were something that we're not. We've tried on an accent from a foreign country, dressed up as a ghost or a gypsy or a gladiator for Halloween or pretended we were smarter or richer to impress a first date.

Is it any wonder that animals do it, too? In nature, it's called mimicry and is a disguise that's a matter of survival. There are well-known examples of visual mimicry — spots that look like eyes on butterflies' wings, snakes that have evolved to resemble their more-venomous relatives.

But scientists are discovering that animals also use smell and even sound for protection. That's why Jesse Barber and William Conner, two researchers at Wake Forest University, think that a certain type of moth has developed a sound similar to one of their less palatable cousins, a sound which can protect them against hungry bats.

Barber, a student who just got his doctorate from WFU in biology, and Conner, an entomologist who specializes in a large family of insects called tiger moths, published a paper in the Proceedings of the National Academy of Sciences in May that outlined the first well-documented example of acoustic mimicry, or mimicry using sounds. "It's a beautiful example of the adaptation of making yourself sound like an animal that is toxic," Conner said.

Bats find moths through echolocation, sonar used by such animals as dolphins and whales, to navigate and find prey. The animals make sounds and then listen for sonic echoes that bounce back from the world around them. For bats, echolocation acts as their eyes in the dark, a compass to tell them where to go and where to find food.

That's how they find moths — the bat's cry bounces off the bug, alerting the bat to dinner's location. For some of the moths that cry is a warning. They have adapted a way of answering the bat, a static chatter made by popping pieces of exoskeleton, called tymbals, that are on the sides of its chest. The sound tells the bat that they are dealing with a potentially bad-tasting insect.

Barber documented this by videotaping bats with highspeed infrared cameras as they stalked moths. Barber exposed the bats to moths that are nontoxic and don't make sounds, moths that were toxic and make sounds, and their mimics — moths that are nontoxic and make sounds.

The moths that mimicked the sounds of their toxic relatives were less likely to get eaten than the moths that didn't make the sounds. A special microphone picked up the low-frequency bat-moth conversations, noises that are well beyond our range of hearing.

In Barber's videos, it's easy to see the difference between the moths that make the protective sounds and those that don't. In one, a bat swoops in, deftly plucking a flapping moth off the end of a fishing line like a dog snapping up a biscuit. Slowed down, the bats' swift aerial acrobatics are the stuff of Olympic high-divers: a doomed moth caught in the bat's billowing tail membrane as the bat elegantly flips into a pool of black space.

But in another video, the bat flies close, then abruptly turns away. The moth is safe and the bat leaves without a meal. "Anything that flies at night has to have some way of dealing with a major predator," Conner said. Some bats — specifically red bats that specialize in eating moths — eventually called the tasty but mimicking moth's bluff. Others, called big browns, continued to avoid them, unwilling to take the risk that they were dealing with the toxic variety.

Barber also removed some moths' tymbals. Unable to mimic any warning, the moths were a quick meal for the bats. "So it's just the sound protecting them;' Barber said. The research was financed by the National Science Foundation.

Barber will spend much of the summer working at the American Museum of Natural History's Southwestern Research Center in the Chiricahua Mountains of southeastern Arizona. There, he will be looking for a rare moth and capturing more bats to study any other variations in their predator-prey dance. Then, in mid-August, he'll start a job with the National Park Service in Colorado as a bioacoustian, listening to sounds collected from national parks and assessing the effects of manmade noise on animals.

Originally, Barber wanted to work with dolphins — not a natural fit for a young scientist who went to a land-locked college (the University of Wyoming in Laramie) and who grew up helping his father, a biologist, tag grizzly bears in Washington state.

But it was echolocation, not just the romantic lure of the intelligent mammals, that fascinated him. While he was at Wyoming, he worked on his master's thesis with a neuroscientist who studies echolocation and how it is processed in bats' brains.

Through the scientific grapevine, Barber heard about Conner's work with bats and moths. Five years ago, Barber started his PhD at Wake, building on the work of an earlier PhD student.For his work, Barber knew that it was important that he used bats that had been raised in a controlled, laboratory environment so that he could be sure that they hadn't had much experience with sound-producing moths. To do that, he collected baby bats from old tobacco

warehouses and from exterminators who removed them from houses, where bats are often found hiding out in attics.

He brought them back to a basement lab in Winston Hall, a dark, high-ceilinged room padded with sound-proofing foam called The Bat Cave. He first fed the babies mealworms by hand and eventually taught them how to catch moths in the air.

Bats and moths have existed in a tense relationship for a long time, maybe millions of years, each listening carefully for the other. Researchers are just beginning to understand some of the intricacies of their existence. "These two groups have a long-term history;' Barber said. "They're been racing back and forth. It's all a sound battle.'

Moth Mimicry, cont’d

Questions:

1] Describe how mimicry becomes an adaptation, using specifics from this example.

2] Compare mimicry and camouflage.

3] What is a bioacoustian and how might their work be a benefit?

4] What special circumstances were involved in how the scientist collected bats?

5] The article covered visual and acoustic mimicry; describe mimicry based on other senses.