According to a new study conducted by researchers from Ogasawara Whale Watching Association and Hokkaido University in Japan, songs sung by male humpback whales are being silenced thanks to human activity.

Relying on songs to navigate, communicate, find mates and locate food, baleen whales such as the humpback and their songs are being drowned out by shipping noises, underwater construction, oil and gas activity, and military sonar.

Although previous studies have revealed that these auditory threats can impact the health of various sea creatures, researchers set out to determine the impact of just one passing ship on humpback whales' songs.

Researchers in Japan relied on underwater recorders to observe how the noise that accompanies just one passing ship impacts whalesongs in locations around the Ogasawara Islands. The team, conducting their research between February 2017 and March 2017, recorded the whalesongs from an estimated one to three different whales each day for a total of 26 different singers.

"This study presents a really special and unique situation," Rosalind Rolland, a whale expert and veterinarian at the Anderson Cabot Center for Ocean Life at the New England Aquarium who did not participate in the research, explained. "It's very difficult to find anywhere in the ocean where there is just a single source of ocean noise. Most times there is noise from all directions."

After reviewing the recordings, the team reasoned that fewer male humpbacks would sing within 500 meters of a shipping lane than any other location. Whales located within 1,200 meters temporarily halted singing, after the passing of a ship, and most whales that stopped did not resume singing again until at least 30 minutes elapsed following the ship's passing.

"Humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song, such as through frequency shifting or source level elevation," the authors wrote in the paper. "Ceasing vocalization and moving away could be cost-effective adaptations to the fast-moving noise source."

The findings are published in the journal PLOS One.

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