The War Between Bats and Moths

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

  Today we're talking about an arms race that's been escalating in our skies - for about 65 million years. The war between Bats and moths is driven by natural selection, which is the engine of evolution. This is how it 

  works: An individual organism is born with a mutation that gives it an advantage for survival. Maybe its better at finding food or avoiding predators, but it lives longer and produces more offspring.

 The new trait is passed through generations. Eventually the descendants out-compete the original species, and become the next evolutionary step. Species can evolve rapidly in an evolutionary arms race. For example, some animals in the Earth's early ocean evolved shells because their predators evolved teeth. The predator evolved a bigger jaw to crush the shell, and on it goes. At Wake Forest University in Winston-Salem Doctor Bill Conner has found an interesting adaptation used by some moths to evade their natural predators, bats.

This story begins 65 million years ago.

That's when the Dinosaurs died. With that competition gone, mammals experienced a rapid, or “punctuated evolution” to fill the niches left behind.

That's when bats evolved and they started using their sophisticated echolocation system, a sonar system to locate their food, Moths. it was a rough time for insects they had to evolve methods for dealing with bats.

And so begins the evolutionary “arms race”.

The first step in this process was the evolution of ears. They can hear the sonar signals and evade the bats. the next step was in a group of moths called the Tiger moths. these animals evolved devices called timbal organs, and they're sound producing. it has a little blister of cuticle and muscles associated with it. When they flex the muscles it buckles inward producing a series of clicks. and when they relax the muscle it produces a second series of clicks. this is the sound that they beam back at the bat.

This is a recording of the timble organ slowed down 30 times.(The audio is from the above video, found at http://www.sonarjamming.com/ ) So, why would a moth communicate with its predator, and how does that give it an advantage for survival? Dr. Conner found a couple of reasons:

There are several species that advertise that the moth is toxic. it's a lot like the bright coloration of the poison arrow frog or the toxic butterfly. But a moth can't use bright coloration at night so it instead uses sound. this moth clicks and it can advertise that toxicity to the bat.

But here's the coolest thing he found..

The moths can actually jam the sonar. the bat produces a high-frequency sound. It beams that out and it listens very carefully for the echo. from the timing of the echo it can determine the distance to the target. now imagine when a moth inserts a series of clicks. those clicks arrive at inopportune moments and the bat can't determine which sound is in fact the echo. bats have a great deal of difficulty locating these months and catching them.

Listen to the sound, slowed down 15 times, of a big brown bat unsuccessfully attacking a clicking moth. Here's the moth. Could you hear the bat's disrupted echolocation sounds?(The audio is from the above video, found at http://www.sonarjamming.com/ ) In nature the arms race is always on. Can you see how plants and animals around you find food, survive predators or adapt to their environment? Learn more about this topic at Aaron Corcoran's web site. http://www.sonarjamming.com/ Aaron Corcoran is a student studying and working with Dr. Conner at Wake Forest University.

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