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Title: Sound variation and function in captive Commerson's dolphins (Cephalorhynchus commersonii)
Authors: Yoshida, Yayoi M.
Morisaka, Tadamichi
Sakai, Mai
Iwasaki, Mari
Wakabayashi, Ikuo
Seko, Atsushi
Kasamatsu, Masahiko
Akamatsu, Tomonari
Kohshima, Shiro
Author's alias: 吉田, 弥生
Keywords: Commerson's dolphin
Acoustic behaviour
Issue Date: Oct-2014
Publisher: Elsevier B.V.
Journal title: Behavioural Processes
Volume: 108
Start page: 11
End page: 19
Abstract: Commerson's dolphin (Cephalorhynchus commersonii), one of the smallest dolphin species, has been reported to produce only narrow-band high-frequency (NBHF) clicks and no whistles. To clarify their sound repertoire and examine the function of each type, we analysed the sounds and behaviour of captive Commerson's dolphins in Toba Aquarium, Japan. All recorded sounds were NBHF clicks with peak frequency >110 kHz. The recorded click-trains were categorised into four types based on the changing pattern of their Inter-click intervals (ICI): Decreasing type, with continuously decreasing ICI during the last part of the train; Increasing type, with continuously increasing ICI during the last part; Fluctuating type, with fluctuating ICI; and Burst-pulse type, with very short and constant ICI. The frequency of the Decreasing type increased when approaching an object newly introduced to the tank, suggesting that the sound is used for echolocation on approach. The Burst-pulse type suddenly increased in front of the object and was often oriented towards it, suggesting that it was used for echolocation in close proximity to the object. In contrast, the Increasing type was rarely recorded during approach, but increased when a dolphin approached another dolphin. The Increasing and Burst-pulse types also increased when dolphins began social behaviours. These results suggest that some NBHF clicks have functions other than echolocation, such as communication.
Rights: © 2014 Elsevier B.V.
This is not the published version. Please cite only the published version. この論文は出版社版でありません。引用の際には出版社版をご確認ご利用ください。
DOI(Published Version): 10.1016/j.beproc.2014.08.017
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