Urban Grasshoppers Lower Their Voices to be Heard Over the Din
PARIS — For city grasshoppers, noise just isn't cricket.
Loud traffic drowns out the song the male grasshopper makes by rubbing a toothed file on his hind legs against a protruding vein on his front wings to lure a mate.
But, German biologists have discovered, the clever insect has found a way to get his offer of romance through the din. Grasshoppers change the song so that it boosts lower-frequency notes, making it audible over the rumble from the road.
Ulrike Lampe and colleagues from the University of Bielefeld captured 188 male bow-winged grasshoppers (Chorthippus biguttulus); half from quiet locations and half from beside busy roads.
The team made nearly 1,000 lab recordings of each grasshopper, placing a cute female grasshopper nearby to encourage a serenade.
"Bow-winged grasshoppers produce songs that include low- and high-frequency components," said Lampe.
"We found that grasshoppers from noisy habitats boost the volume of the lower-frequency part of their song, which makes sense since road noise can mask signals in this part of the frequency spectrum."
The findings add insects to the list of animals, including species of birds, whales and frogs, that have been found to alter their sounds in order to cope with man-made noise.
Bow-winged grasshoppers are a common species in central Europe. The male's courtship song consists of up to half a dozen phrases, each about two or three seconds long. The phrase starts with a ticking sound, becomes louder, and ends in a buzz.
Image: Hamed Saber / via Flickr