Noise pollution from cargo ships can stop the singing of male humpback whales, a study has suggested.
Researchers found that whales living around the Ogasawara Islands in Japan stopped or reduced their singing in reaction to low-frequency shipping noise.
The study, by the Ogasawara Whale Watching Association and Hokkaido University in Japan, used two underwater recorders to capture whale song between February and May 2017.
It found fewer of the creatures sang within 500m of the shipping lane than elsewhere when a ship passed through the remote area.
Whales within 1,200m tended to temporarily reduce or stop their singing after the ships passed, with most of the creatures not resuming their songs for at least half an hour.
Researchers have not definitively pinned down why the mammals make the complex repetitive vibrations.
All the males in a population sing the same song, which changes over time. Females and calves do not sing.
The study captured the singing of one to three whales per day, and 26 singers in total.
Its authors said future research could look into the effects of “more continuous noise exposure as a possible stressor for the whales”.
The authors said: “Humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song under the noise, generated by a passenger-cargo liner.
“Ceasing vocalisation and moving away could be cost-effective adaptations to the fast-moving noise source.”