Grasshoppers are having to change their song – one of the iconic sounds of summer – to make themselves heard above the din of road traffic, ecologists have discovered. The study, published in the British Ecological Society's journal Functional Ecology, is the first to show that man-made noise affects natural insect populations.
Animals use sound to communicate for many reasons, including marking out territory, warning of predators and finding mates, and although previous research shows birds, whales and even frogs alter their calls in noisy environments, the impact of man-made noise on insects has been neglected until now. Ulrike Lampe and colleagues from the University of Bielefeld in Germany caught 188 male bow-winged grasshoppers (Chorthippus biguttulus), half from quiet locations and half from beside busy roads. The grasshoppers use their song – produced by rubbing a toothed file on their hind legs against a protruding vein on their front wings – to attract mates.
The team then studied the differences in the two groups' songs in the laboratory. To encourage them to sing they exposed the males to a female grasshopper, and then recorded their courtship songs. Analysis of almost 1,000 recordings revealed grasshoppers living beside noisy roads produced different songs to those living in quieter locations.
According to Lampe: "Bow-winged grasshoppers produce songs that include low and high frequency components. 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 team's findings are important because traffic noise could be upsetting the grasshopper's mating system. "Increased noise levels could affect grasshopper courtship in several ways. It could prevent females from hearing male courtship songs properly, prevent females from recognising males of their own species, or impair females' ability to estimate how attractive a male is from his song," Lampe explains.
Having discovered that man-made noise affects insect communication, the researchers now want to learn more about how the mechanism works, and whether the grasshoppers adapt to noise during their development as larvae, or whether males from noisy habitats produce different songs due to genetic differences.
The bow-winged grasshopper is a common species in Central Europe. Adults occur mainly between July and September, preferring dry grasslands. Around 1.5 cm long, they vary in colour from green and browns to red and purple. The male's song consists of 2 second-long phrases that increase in amplitude towards the end. The beginning of a phrase is characterised by slower ticking sounds that increase in speed and amplitude, leading to a buzzing sound towards the end of the phrase. A courtship song usually includes 2 phrases.
Ulrike Lampe, Tim Schmoll, Alexandra Franzke and Klaus Reinhold (2012). 'Staying tuned: grasshoppers from noisy roadside habitats produce courtship signals with elevated frequency components', doi: 10.1111/1365-2435.12000, is published in Functional Ecology on Wednesday 14 November 2012.
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
After 30 years working in mountain regions, Jack Ives argues that the world's elevated habitats are essential
Long-range tracking technology will help researchers understand bee behavior.
Rising temperatures in the coming years may result in less tasty vegetables, meat and dairy products, report says
Americans concerns near record lows
In South Florida, the world's two most destructive termite species could be mating because of climate change. Researchers say if the hybrids colonize, they could pose an even greater economic threat.
War, pestilence, even climate change, are trifles by comparison. Destroy the soil and we all starve
Director of the charitable trust, Jeremy Farrar, says retaining fossil fuel shares gives more influence over such companies – but they would not rule out divesting in the future, should engagement prove ineffective
ROME (Thomson Reuters Foundation) - Scientists have bred 30 new varieties of "heat-beating" beans designed to provide protein for the world's poor in the face of global warming, researchers announced on Wednesday.
Climate change-related rising sea levels are expected to intensify erosion; "It's half of our economy"
Animal rights groups hope an appeals court will help free the orca Lolita from a Miami aquarium where it has lived since 1970