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Noisy neighbourhood changes whale song


Is man-made noise degrading the habitat of marine mammals?

Recent research suggests a justification for concerns that man-made noise is degrading the environment of marine mammals dependent on sonar for navigation and communication.

In a study published in Nature, biologists from the Woods Hole Oceanographic Institution Massachusetts, working in conjunction with the U.S. Navy, found the behaviour of the male humpback whale was altered by the presence of man-made noise.

The study attempted to determine to what degree the sexual displays (singing) of the male humpback were affected when exposed to Low Frequency Active (LFA) sonar. The report suggests the humpbacks sang longer during the transmission to compensate for acoustic interference.

Researchers continuously followed and recorded the singing of 16 male humpbacks for several hours by towing a calibrated hydrophone from their observation vessel.

A Navy vessel then transmitted 10, 42-second LFA sonar signals at six-minute intervals. The whales were exposed to signals no louder than 150 dB.

The report states the humpbacks' songs were "on average, 29% longer during the LFA playback - a particularly strong result, given the low power of the test and the small sample size".

It was also found that song duration returned to normal after the transmission was stopped.

Tags: marine-biology