The loud noise of modern life can have a serious impact on animals (SN: 2/9/15). Traffic noise can cover up mating calls, increase stress hormones, and raise mortality rates. Now, new research suggests that some animals can be harmed by this noise even before they are able to hear it.
Zebra finch eggs and young birds exposed to everyday traffic noise experience significant, long-lasting decreases in health and reproduction, scientists report in the April 26 Science. This harm came from direct exposure to the sound itself, indicating that noise pollution is a more widespread threat than previously believed.
“We were really surprised,” says Mylene Mariette, a behavioral ecologist at Deakin University in Geelong, Australia. “Not just because the effects were strong, but they lasted a long time.”
Previous research connected noise exposure during development to health issues later in life, but scientists couldn’t be sure whether it was due to noise affecting parenting.
Mariette and colleagues changed the sound environment for zebra finches (Taeniopygia guttata castanotis) before and after birth, exposing them to traffic noise or birdsong overnight as eggs, chicks, or during both life stages. Crucially, young birds were separated from their parents for the sound treatments.
Traffic noise during only the egg or young bird stage had negative effects, and it was worse for birds exposed to the sounds at both stages. Noise-exposed eggs hatched less often than song-exposed eggs. Twelve days after hatching, noise-exposed birds were 14.5 percent lighter, on average. And telomeres, which are repetitive DNA sequences at the tips of chromosomes, were also 38 to 46 percent shorter, on average, for noise-exposed birds. Shorter telomeres can indicate higher physiological stress (SN: 7/9/16).
The impacts continued into adulthood. In an enclosure where zebra finches were allowed to breed freely, noise-exposed birds produced 59 percent fewer offspring — about four less birds — than those raised amid natural sounds. The effect was mainly due to prenatal exposure, the team found.
Overall, the results suggest “an innate and spontaneous response to noisy stimuli,” Mariette says. What exactly causes this response is still unknown, she says, but “it’s likely something that is shared across species.”
