Grasshoppers change tune to cope with traffic noise

Grasshoppers in urban areas have changed their mating calls to cope with the traffic noise, scientists say.

Researchers suggest that high levels of background noise may affect the grasshoppers’ mating process, as the insects are forced to increase the volume of the low-frequency sections of their call.

According to lead researcher Ulrike Lampe, the first of its kind research shows traffic noise could upset bow-winged grasshoppers’ (Chorthippus biguttulus) mating system, the ‘BBC News’ reported.

“Effects of man-made noise on acoustic communication has only been studied with vertebrates, so far,” said Lampe, a PhD student at the University of Bielefeld’s Department of Evolutionary Biology. The scientists caught 188 male bow-winged grasshoppers from noisy roadsides and quiet rural locations. “Bow-winged grasshoppers are a good model organism to study sexual selection because females can respond to male courtship songs with their own low-frequency acoustic signal, if they are attracted to a male song,” said Lampe. The grasshoppers produce their mating call by rubbing a toothed file on their hind-legs against a protruding vein that is located on their front wings.

The male’s song consists of short phrases of two to three seconds that increase in amplitude towards the end.

The first part of the call comprises slower ticking sounds that increase in speed and amplitude, leading to a buzzing sound towards the end of the phrase, the report said.
In order to stimulate the males to begin mating calls, scientists exposed the males to a female and recorded the results in the laboratory.

The team then analysed the differences between the results of each group of grasshoppers. Results showed that compared to males from rural locations, urban grasshoppers “shift the frequency peak of the lower part of their spectrum upwards,” Lampe said.

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