The Grasshopper and the Noisy City

            

             The sound of grasshoppers chirping at night is a familiar sound for many people - especially those of us who grew up in smaller cities or live in the country. I know that I find the sound very comforting - Mother Nature's natural lullaby if you will. So I find myself shocked because one particular species of European grasshopper has evolved its mating call to overcome the din of modern city noise.

            Apparently, the frequency of much city noise - cars, construction, etc is on a similar level of the frequency of the bow-winged grasshopper's mating call. This noise may have been interfering with the females hearing the calls and the males hearing the females responses. This obviously has a detrimental effect on the grasshopper's population in the city, so they have changed their call enough to be differentiable from the other noise.

            You may be asking yourself - How do we know that it is an evolution and not just a modification? There have been other animals known to modify their mating calls to fit an environment by either changing their timing or their volume.

            To prove that this was in fact an evolutionary trait, researchers at the University of Bielefeld, Germany, collected specimens from a city environment and a rural one. They then put the specimens in an isolated environment with none of the city noises. When they put the males in the proximity of females, the city grasshoppers were found to have a mating call of a higher frequency!

            As a race, we have actually caused a threat to population that caused an evolutionary change. Pretty cool, huh? While it isn't good that we have interfered with their natural order that much - it is a fascinating look into the process of evolution. Perhaps from this we can gleam more understanding of the process of evolution and the factors that trigger it.

Full article (audio clip of chirp too) - here

Discover mag. blog - here