Living in the city in a noisy experience, but though the ruckus may irritate humans, research is showing that it could have way worse effects on a variety of birds and other animals who use sound to attract mates.

Many animals are attracted to males with deep voices, usually in the range of about 1 kilohertz to 10 kilohertz (the measure of the number of times a sound oscillates per second). Just so happens this is about the same pitch made by city traffic. Studies are now showing that birds, crickets, frogs and other animals living in these environments are pitching up their voices to be heard over the din. One study showed that a species of city-dwelling frogs were shifting their pitch upward by 5 percent, while some grasshoppers changed their pitch by 4 percent.

This is worrying for a few reasons. Studies on a variety of animals, including humans, have shown that females often judge a male's virility and worthiness as a mate by the deepness of his voice. Scientists are now concerned that these pitch-shifting creatures could end up choosing inappropriate mates.

"Females could be making poor choices," Kirsten Parris, a researcher at the University of Melbourne on the effects of urban noise on amphibians told Nautilus. "They can no longer hear that Bob has more energy than Frank." This lack of judgement could mess up the process of natural selection, causing species to be less successful. One 2010 study showed that the great tit bird lay 10 percent fewer eggs alongside a Dutch roadway when the traffic noise was the same pitch as the bird's mating song.

There's still disagreement within the scientific community on whether the noise of cities is actually negatively affecting bird species. Leiden University associate professor Hans Slabbekoorn, who has studied the affect of human noise on animals for 15 years, says that there is "clear and replicated experimental evidence for noise-dependent shifts in the pitch of several animal species, but this does not mean that all species will change the pitch of their song." More research must be done to prove that these findings are as widespread as some scientists fear.

City life isn't for everyone.

Source: Nautilus

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