Abstract
Reactions of singing behavior of individual humpback whales (Megaptera novaeangliae) to a specific shipping noise were examined. Two autonomous recorders separated by 3.0 km were used for the acoustic monitoring of each individual song sequence. A passenger-cargo liner was operated once per day, and other large ship noise was excluded given the remote location of the Ogasawara Islands, 1000 km south of Tokyo. In total, locations of between 26 and 27 singers were measured acoustically using time arrival difference at both stereo recorders on the ship presence and absence days, respectively. Source level of the ship (157 dB rms re 1μPa) was measured separately in deep water. Fewer whales sang nearby, within 500 m, of the shipping lane. Humpback whales reduced sound production after the ship passed, when the minimum distance to the whale from the ship trajectory was 1200 m. In the Ogasawara water, humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song such as through frequency shifting or source level elevation. This could be a cost effective adaptation because the propagation loss at 500 m from the sound source is as high as 54 dB. The focal ship was 500 m away within several minutes. Responses may differ where ship traffic is heavy, because avoiding an approaching ship may be difficult when many sound sources exist.
Highlights
Ocean noise caused by human activities has been rapidly increasing in recent years
We focused on a passenger-cargo ship’s noise and the singing behavior of humpback whales in the Ogasawara Islands
We obtained two sets of singing behavior of humpback whales within a known distance from the subject ship when the ship was on its closest approach to them
Summary
Ocean noise caused by human activities has been rapidly increasing in recent years. Andrew et al [1] indicated that low-frequency noise levels in the ocean increased by 10 dB between 1960s and 1990s. McDonald et al [2] suggested that average noise levels would increase by 2.5–3 dB per decade. The sources of low-frequency noise are seismic explosion, transportation, harvesting renewable energy, and military sonar. The main noise source is presumed to be from commercial ships [1,2,3]. There has been concern about the effect of anthropogenic noise on marine creatures, including fishes and marine mammals (e.g., [4,5,6,7]).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
