Given a high enough level of traffic noise, owls lose nearly 90% of their hunting efficiency, according to researchers from Hokkaido University.
In a new study published in the journal Scientific Reports, researchers from the university report their findings on the impact of noise on long- and short-eared owls.
Owls are among those predators, like bats, that rely heavily on their sharp hearing in order to find food. The team's results highlight just how much that is the case.
RELATED: New Owl Species Arises from Case of Mistaken Identity
According to the researchers, theirs is the first study to back up the notion in the wild that traffic noise hinders owls' ability to forage. Previously, the animals' hunting after dark had been hard to observe. As a workaround, the scientists created a battery of artificial prey sounds that would attract the owls.
The team studied 78 owls (45 short-eared, 33 long-eared) in sites in northern Japan, playing them the artificial prey sounds at a steady decibel level while also playing varying levels of pre-recorded traffic noise.
When the traffic noise was lowest, about 40 decibels, the owls lost about 17% of their ability to hear the prey sounds over the road sounds. However, when traffic was at its noisiest –- about 80 decibels; equivalent to being in a train, according to the scientists –- the birds lost 89% of their capacity to hear the prey.
The loss of hunting efficiency came from combinations of the masking of prey sounds by traffic, distraction created by the noise, and simple aversion to the noise, the team said.
What's more, they estimate the traffic sounds impact owl hearing as far as 394 feet (120 meters) from the source, a distance that was higher than the researchers expected to find.
RELATED: How Owls Spin Heads Around
"Behavioral changes in acoustic predators can alter the interactions between prey and predators and possibly have negative consequences on the entire ecosystem," said study co-author Futoshi Nakamura, in a statement.
To figure out how to soften the impact of traffic sounds on the predators, the researchers say further discoveries about the mechanisms behind the hearing loss will be needed. They'll also need to gauge the impact of the traffic on the birds' choice of habitat and their survival rate.
SEE PHOTOS: All Eyes on Owls