Acoustic repertoires related to surface behaviours of the Irrawaddy dolphins (Orcaella brevirostris) in Brunei Bay, Malaysia

Hairul Masrini Muhamad and Xu, X. and Zhang, X.L. and S.A. Jaaman and A.M. Muda and F.D. Haji Ismail and N. Azizul (2022) Acoustic repertoires related to surface behaviours of the Irrawaddy dolphins (Orcaella brevirostris) in Brunei Bay, Malaysia. ASM Science Journal, 17. pp. 1-13. ISSN 1823-6782

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URL: https://www.akademisains.gov.my/asmsj/article/acou...

Abstract

Behavioural observation and acoustic recordings of Irrawaddy dolphins (Orcaella brevirostris) were performed simultaneously in Brunei Bay, Malaysia. Surface behavioural observations were classified into four categories: travelling, foraging, socialising, and milling. A total of 8.43 hours of acoustic recordings were used to retrieve four different types of sounds: whistles, burst-pulsed sounds, click trains, and biphonal sounds. The recorded whistles were frequency-modulated sounds with durations ranging from 0.06 to 3.86 s and a mean minimum frequency of 6.5±2.5 kHz. The burst-pulsed frequency ranged from >48 kHz in at least four variations. Click trains were made up of broadband clicks with variable inter-click intervals and frequencies >48 kHz. The first biphonic sounds for Irrawaddy dolphins have been revealed in this study. Whistle rates were extremely high in milling. Compared to travelling and foraging, socialising had a significantly higher rate of click trains. Across all surface behaviours, there was no significant difference in burst-pulsed rates. This study laid the groundwork for ongoing monitoring of Irrawaddy dolphins and expanding conservation efforts for this species in Malaysia

Item Type:	Article
Keyword:	Irrawaddy dolphins , Orcaella brevirostris , Sounds , Surface behaviours
Subjects:	Q Science > QL Zoology > QL1-991 Zoology > QL605-739.8 Chordates. Vertebrates > QL700-739.8 Mammals
Department:	INSTITUTE > Borneo Marine Research Institute
Depositing User:	SAFRUDIN BIN DARUN -
Date Deposited:	28 Oct 2022 13:54
Last Modified:	28 Oct 2022 13:54
URI:	https://eprints.ums.edu.my/id/eprint/34581

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