Long-term acoustic monitoring of nonstereotyped blue whale calls in the southern Indian Ocean
Type | Article | ||||||||||||||||||||
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Date | 2023-04 | ||||||||||||||||||||
Language | English | ||||||||||||||||||||
Author(s) | Torterotot Maëlle1, Samaran Flore1, Royer Jean-Yves2 | ||||||||||||||||||||
Affiliation(s) | 1 : Lab-STICC UMR 6285, ENSTA Bretagne, Brest, France 2 : Geo-Ocean UMR 6538, CNRS, Université de Brest, Brest, France |
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Source | Marine Mammal Science (0824-0469) (Wiley / Blackwell), 2023-04 , Vol. 39 , N. 2 , P. 594-610 | ||||||||||||||||||||
DOI | 10.1111/mms.12998 | ||||||||||||||||||||
Keyword(s) | Antarctic blue whale, Balaenoptera musculus, D-calls, passive acoustic monitoring, pygmy blue whale, southern Indian Ocean | ||||||||||||||||||||
Abstract | Monitoring the presence of blue whale (Balaenoptera musculus ssp.) stereotyped calls has been a widely used method to assess the different populations' distribution worldwide. All blue whale populations also produce nonstereotyped vocalizations, or D-calls. Here, we monitored the presence of D-calls in long-term records from a large hydrophone array located in the open southern Indian Ocean, using an automated detection method and manual validation of the detections. D-calls were detected at all sites of the array, which extends from 24°S to 56°S, but the majority of them were detected at the two southernmost sites. We observed a latitudinal shift in their seasonal occurrence, with more D-calls in the north during austral autumn and winter and more in the south during austral spring. The geographical occurrence of D-calls compared to that of songs indicates that blue whale acoustic behavior switches from a song-intensive and sparse-D-call emission in the north to song-moderate and more intensive D-call emissions in the south. These findings support the hypothesis that both call types are used for different purposes, as D-calls are mainly detected around foraging grounds and songs in wintering grounds. Monitoring both call types might therefore be a relevant acoustic indicator of blue whale behavior. |
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