FOR KIDS: How a bat sneaks up
All you moths out there, listen carefully. A scientist named Holger Goerlitz has some bad news. You probably already know that bats want to eat you. But Goerlitz and his colleagues have found that the Western barbastelle bat of Europe whispers so quietly you’ll never hear it coming. So look out, and good luck. You’ll need it.
Perhaps there’s nothing scarier to a moth than a quiet bat.
Bats are basically blind. (Ever heard the expression, “Blind as a bat”?) Since they can’t rely on their eyes to hunt for food, these flying mammals use sound. Bats let out a high-pitched noise in the night, and the sound waves bounce off nearby objects — such as delicious moths.
Bats hear this echo, figure out where it came from, and then move in for the kill. This technique — using an echo to locate food — is called echolocation. No surprise there.
The problem with most bats is that they’re loud. Previous studies have found that when some bats make their echolocation sounds in the night, they’re louder than rock concerts and sometimes as loud as jet engines. As a result, some moths can hear some of these sounds from nearly 100 feet away — plenty of warning. These sounds are “high notes”— so high that human beings, with our limited ears, cannot hear them.
That’s “quite lucky for us,” Goerlitz told Science News. As a biologist at the University of Bristol, in the United Kingdom, Goerlitz studies the ways animals interact with each other in their environments.
In some flying insects, like moths, simple ears evolved — giving those creatures the ability to hear noises in the night and avoid becoming a bat’s dinner. Moths with ears have a fighting chance to fly away from hungry bats.
Goerlitz’s research suggests that bats found a way to get around moths that can hear. The sounds of other bats are ten to a hundred times louder than what the Western barbastelle bat of Europe can send out. Its quieter sounds are like a bat “whisper.” Moths can’t hear this high-pitched whisper until it’s too late to get away.
To study the bats and moths, Goerlitz and his colleagues set up many microphones in an area where bats would pass through in the night. When a bat made its high-pitched sound, many of the microphones picked up the noise.
The scientists could determine the location of the bat by comparing the sound signals from one microphone to another. This comparison made it possible to calculate that the sound of the barbastelle bat isn’t heard by a moth until the bat is only about 11 feet away — which is often too close for escape.
The researchers didn’t stop there. They studied the poop from the barbastelle bats in the area to see what the animals were eating. Almost 90 percent of the barbastelle bats’ diet was moths, and 85 percent of those moths were the type that have ears. That means that the main course for these “whispering” bats is moths that can hear.
Goerlitz says it makes sense that bats would want to eat moths — though when he says it, he sounds a little batlike himself. “Moths are nice food,” he told Science News. “They are big and fat and have a lot of energy.”
Echolocation A sensory system in certain animals, such as bats and dolphins, in which usually high-pitched sounds are emitted and their echoes interpreted to determine the direction and distance of objects.
Mammal Any of various warm-blooded vertebrate animals of the class Mammalia, including humans, characterized by a covering of hair on the skin and, in the female, milk-producing mammary glands for nourishing the young.
Evolve To develop (a characteristic) by evolutionary processes.
Biology The science of life and of living organisms, including their structure, function, growth, origin, evolution and distribution.