Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean
In 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 7years of continuo...
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ftarchimer:oai:archimer.ifremer.fr:62730 2023-05-15T13:47:36+02:00 Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean Leroy, Emmanuelle C Royer, Jean-yves Bonnel, Julien Samaran, Flore 2018-11 application/pdf https://archimer.ifremer.fr/doc/00516/62730/67109.pdf https://doi.org/10.1029/2018JC014352 https://archimer.ifremer.fr/doc/00516/62730/ eng eng Amer Geophysical Union https://archimer.ifremer.fr/doc/00516/62730/67109.pdf doi:10.1029/2018JC014352 https://archimer.ifremer.fr/doc/00516/62730/ info:eu-repo/semantics/openAccess restricted use Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2018-11 , Vol. 123 , N. 11 , P. 8568-8580 large baleen whales blue whale calls frequency shifts frequency decrease ambient noise bioacoustics text Publication info:eu-repo/semantics/article 2018 ftarchimer https://doi.org/10.1029/2018JC014352 2021-09-23T20:33:28Z In 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 7years 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. Plain Language Summary In the past decades, a progressive decrease in the frequencies of blue whale vocalizations is observed worldwide. Its causes,of natural or anthropogenic nature, are unclear. Based on 7years of widespread acoustic records in the southern Indian Ocean, we show that the call frequency of five populations of large baleen whales decreases at a constant rate of tenths of hertz per year. We also found that seasonal shifts in the whale call frequency follow seasonal changes in the ambient noise in the same frequency band. Wide-ranging changes in the acoustic environment have thus a strong impact on the vocal behavior of large whales in the short term, but, paradoxically, not in the long term. Article in Journal/Newspaper Antarc* Antarctic baleen whales Blue whale Iceberg* Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Antarctic Indian Journal of Geophysical Research: Oceans 123 11 8568 8580 |
institution |
Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
topic |
large baleen whales blue whale calls frequency shifts frequency decrease ambient noise bioacoustics |
spellingShingle |
large baleen whales blue whale calls frequency shifts frequency decrease ambient noise bioacoustics Leroy, Emmanuelle C Royer, Jean-yves Bonnel, Julien Samaran, Flore Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean |
topic_facet |
large baleen whales blue whale calls frequency shifts frequency decrease ambient noise bioacoustics |
description |
In 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 7years 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. Plain Language Summary In the past decades, a progressive decrease in the frequencies of blue whale vocalizations is observed worldwide. Its causes,of natural or anthropogenic nature, are unclear. Based on 7years of widespread acoustic records in the southern Indian Ocean, we show that the call frequency of five populations of large baleen whales decreases at a constant rate of tenths of hertz per year. We also found that seasonal shifts in the whale call frequency follow seasonal changes in the ambient noise in the same frequency band. Wide-ranging changes in the acoustic environment have thus a strong impact on the vocal behavior of large whales in the short term, but, paradoxically, not in the long term. |
format |
Article in Journal/Newspaper |
author |
Leroy, Emmanuelle C Royer, Jean-yves Bonnel, Julien Samaran, Flore |
author_facet |
Leroy, Emmanuelle C Royer, Jean-yves Bonnel, Julien Samaran, Flore |
author_sort |
Leroy, Emmanuelle C |
title |
Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean |
title_short |
Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean |
title_full |
Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean |
title_fullStr |
Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean |
title_full_unstemmed |
Long-Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean |
title_sort |
long-term and seasonal changes of large whale call frequency in the southern indian ocean |
publisher |
Amer Geophysical Union |
publishDate |
2018 |
url |
https://archimer.ifremer.fr/doc/00516/62730/67109.pdf https://doi.org/10.1029/2018JC014352 https://archimer.ifremer.fr/doc/00516/62730/ |
geographic |
Antarctic Indian |
geographic_facet |
Antarctic Indian |
genre |
Antarc* Antarctic baleen whales Blue whale Iceberg* |
genre_facet |
Antarc* Antarctic baleen whales Blue whale Iceberg* |
op_source |
Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2018-11 , Vol. 123 , N. 11 , P. 8568-8580 |
op_relation |
https://archimer.ifremer.fr/doc/00516/62730/67109.pdf doi:10.1029/2018JC014352 https://archimer.ifremer.fr/doc/00516/62730/ |
op_rights |
info:eu-repo/semantics/openAccess restricted use |
op_doi |
https://doi.org/10.1029/2018JC014352 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
123 |
container_issue |
11 |
container_start_page |
8568 |
op_container_end_page |
8580 |
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1766247513178767360 |