It's no longer breaking news that noise pollution harms wildlife. In particular, anthropogenic noise in the world's oceans has been shown to interrupt marine animals' communication and navigation, and has even been blamed for driving beak nose whales to beach themselves en masse. But little research has focused on the effect of noise pollution on growing animals. Now, a new study published today in Biology Letters finds that traffic noise can have a significant effect on baby birds, with consequences that could carry over into adulthood.
Most research on noise pollution has zeroed in on the "masking effect" of human-made sounds—that is, their tendency to interfere with the acoustic signals many animals, including birds, use to communicate, according to Alizée Meillère, an ecologist at the Centre d'Etudes Biologiques de Chize in France, and lead author on the new study. But this new work goes beyond the masking effects of noise. "We were able to see that anthropogenic noise can have particularly complex effects on vertebrates’ development," Meillère says. "And that despite any obvious immediate consequences, noise exposure may entail important costs for developing organisms later in life."
"Noise exposure may entail important costs for developing organisms later in life."
To find out what effect traffic noise might have on developing birds, a research group in France played back traffic sounds to breeding pairs of wild house sparrows settling down in nest boxes every day for six hours during the weeks leading up to egg laying, up until the chicks were fully reared. (Control nest boxes were serenaded by the local sounds of the rural study site.)
Nine days after the birds hatched, the team measured the body size and weight of the nestlings, assessed their body condition, and took blood samples to measure corticosteroid levels and telomere length, indications of stress and longevity, respectively. Eight days later, they returned to measure fledgling success.
It turned out that traffic noise didn't affect the birds' size, condition, or ability to fledge, but it did seem to give the young birds significantly shorter telomeres—the non-coding stretches of repeating DNA sequences on the tips of chromosomes that keep organisms from losing critical genetic information when cells divide and chromosomes inevitably shorten. This is bad news for the nestlings exposed to chronic noise pollution, as short telomeres hasten DNA replication errors and may shorten lifespans.
The question of how noise pollution leads to shorter telomeres remains, for now, unanswered. But the study is a fitting reminder that humans have a profound influence on the environment, even if the full consequences of our actions sometimes aren't so apparent. "If we only look for immediate or obvious effects [of pollution] we can miss important and more subtle effects—the 'hidden' impacts of noise exposure," Meillère says. And those costs might extend to other vertebrates as well. "Because vertebrates share very similar physiological mechanisms, it could also mean that noise may have similar impacts on other vertebrates—even humans," she says. "But it would need to be tested of course."
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