Discover A New Feeding Strategy...

SciWorks Radio is a production of 88.5 WFDD and SciWorks, the Science Center and Environmental Park of Forsyth County, located in Winston-Salem.

One of the most basic necessities for survival, and one of my personal favorites, is the acquisition of food. In nature, strategies have evolved giving organisms competitive advantages to do this. In a previous SciWorks Radio episode, we spoke with Dr. Bill Connor, Professor of Biology at Wake Forest University. He told us about a unique evolutionary adaptation in a species of moth, that confuses its predator, the big Brown Bat and gives the moth an advantage for survival. Hear this past episode at WFDD.org. In this episode, we check back in to discuss an interesting, newly-discovered feeding strategy found in the Mexican free-tailed Bat.

Bat calls go from high to low frequency. They go from high to low tone noises.

Bat research is usually done close to the ground. However, Dr. Conner's then student, now collaborator Aaron Corcoran recently discovered a new bat signal by pointing his equipment further up into the sky.

This special signal is a sine FM signal, so it sounds a bit like a siren. They produce it when they're in competition for food with another bat. Imagine two bats approaching a target. The lead bat is echo-locating its target moth. It's sending out bat cries, and it's listening for the echoes. And from the echoes it determines the exact location of the target. The following bat is waiting, and at the moment of truth, he produces this sonar jamming signal, this sine FM signal. It's only produced when the lead bat is about to make a capture. And this is when the lead bat is listening very intently for echoes because its trying to locate the exact position of the moth. And it causes the lead bat to miss the target. And then the following bat, the jamming bat, cleans up and takes the moth.

The full function of a newly-found animal behavior doesn't always present itself. Usually researchers need first to eliminate other possible explanations.

Maybe the signals were actually assisting other individuals of the same species. maybe the bat was running off a competitor. And then also there's a possibility that the sound just startles the bats. One of the keys is what a jamming bat does after it jams the competitor. It doesn't chase that animal out of the area. Instead, it immediately turns its attention to the last known position of the moth. So it's intent on eating.

Observation is only one part of scientific discovery. Confirming the jamming hypothesis required experimentation.

We also did playback experiments in the field. Aaron suspended a moth on a fishing line so that free-flying bats could come in and take the moth. And then he played different sounds: the sine FM signal, the sine FM signal a little too early or a little too late. He played a constant frequency tone that covers the same frequency range as the sine FM, and that would sound more or less like a “Boooooooooo." He also played a white noise, so it would be sort of a “Shhhhhh." And he tested all of these in their ability to make the bat mistake the target. The only one that was successful was the sine FM signal.

Many evolutionary adaptations develop from previously-existing traits or processes.

Evolution is an amazing thing. Since this animal has fifteen different social calls, you could imagine that this sonar jamming call evolved from another social call that was used in a different context. And then it was finely tuned to overlap the bat echolocation cries, and this would then influence the ability of the lead bat to catch the moth, and give the sonar jamming bat an advantage. Whenever you point all this technology at the nighttime sky, you're bound to learn something new. Most scientists don't work at night. So we have an advantage in taking all of this material into the field in the evening, and we're bound to discover new things when we do that. And this is just one example.

This Time Round, the theme music for SciWorks Radio, appears as a generous contribution by the band Storyman and courtesy of UFOmusic.com.