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dc.contributor.authorLeroy, Emmanuelle C.  Concept link
dc.contributor.authorRoyer, Jean-Yves  Concept link
dc.contributor.authorBonnel, Julien  Concept link
dc.contributor.authorSamaran, Flore  Concept link
dc.date.accessioned2019-01-24T20:12:19Z
dc.date.available2019-05-27T08:03:56Z
dc.date.issued2018-11-27
dc.identifier.citationLeroy, E. C., Royer, J.-Y., Bonnel, J., & Samaran, F. (2018). Long-term and seasonal changes of large whale call frequency in the southern Indian Ocean. Journal of Geophysical Research: Oceans, 123, 8568–8580.en_US
dc.identifier.urihttps://hdl.handle.net/1912/10837
dc.descriptionAuthor Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 1123(11), (2018): 8568-8580. doi: 10.1029/2018JC014352.en_US
dc.description.abstractIn the past decades, in the context of a changing ocean submitted to an increasing human activity, a progressive decrease in the frequencies (pitch) of blue whale vocalizations has been observed worldwide. Its causes, of natural or anthropogenic nature, are still unclear. Based on 7 years of continuous acoustic recordings at widespread sites in the southern Indian Ocean, we show that this observation stands for five populations of large whales. The frequency of selected units of vocalizations of fin, Antarctic, and pygmy blue whales has steadily decreased at a rate of a few tenths of hertz per year since 2002. In addition to this interannual frequency decrease, blue whale vocalizations display seasonal frequency shifts. We show that these intra‐annual shifts correlate with seasonal changes in the ambient noise near their call frequency. This ambient noise level, in turn, shows a strong correlation with the seasonal presence of icebergs, which are one of the main sources of oceanic noise in the Southern Hemisphere. Although cause‐and‐effect relationships are difficult to ascertain, wide‐ranging changes in the acoustic environment seem to have a strong impact on the vocal behavior of large baleen whales. Seasonal frequency shifts may be due to short‐term changes in the ambient noise, and the interannual frequency decline to long‐term changes in the acoustic properties of the ocean and/or in postwhaling changes in whale abundances.en_US
dc.description.sponsorshipThe authors wish to thank the Captains and crews of RV Marion Dufresne for the successful deployments and recoveries of the hydrophones of the DEFLOHYDRO (Royer, 2008) and OHASISBIO (Royer, 2009) experiments. French cruises were funded by the French Polar Institute (IPEV) with additional support from INSU‐CNRS. NOAA/PMEL also contributed to the DEFLOHYDRO project. E. C. L. was supported by a PhD fellowship from the University of Brest and from the Regional Council of Brittany (Conseil Régional de Bretagne). The contribution of Mickael Beauverger at LGO to the logistics and deployment of the OHASISBIO cruises is greatly appreciated. The data underlying this analysis (weekly averaged frequencies of Antarctic blue whales, pygmy blue whales, and fin whales and daily averaged noise levels at each site) are accessible at http://doi.org/10.17882/51007.en_US
dc.publisherAmerican Geophysical Unionen_US
dc.relation.urihttps://doi.org/10.1029/2018JC014352
dc.subjectlarge baleen whalesen_US
dc.subjectblue whale callsen_US
dc.subjectfrequency decreaseen_US
dc.subjectbioacousticsen_US
dc.subjectfrequency shiftsen_US
dc.subjectambient noiseen_US
dc.titleLong-term and seasonal changes of large whale call frequency in the Southern Indian Oceanen_US
dc.typeArticleen_US
dc.description.embargo2019-05-27en_US
dc.identifier.doi10.1029/2018JC014352


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