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Preliminary analysis of echolocation signals produced by fleeing Irrawaddy dolphins (Orcaella brevirostris)

Authors

Ying, Jiang; Xuelei, Zhang; Zhiguo, Yang; Arifin, Jaaman Saifullah; Qinzeng, Xu; Marzuki, Muda Azmi; Masrini, Muhamad Hairul

Year

2019

Journal

Acta Oceanologica Sinica

Volume

38

Issue

1

Pages

85-89

Keywords

acoustic behavior, Brunei Bay, disturbance, dolphin, Irrawaddy dolphin, Malaysia, orcaella brevirostris, Underwater noise, whale watching

Abstract

In this study, echolocation signals were recorded from a wild Irrawaddy dolphin (Orcaella brevirostris) in shallow water in the Bay of Brunei. During sound recording, a small fishing boat engine startled a nearby Irrawaddy dolphin and began chasing it on two occasions. Variations in the acoustic parameters were detected. When the Irrawaddy dolphin was startled and chased, the sound pressure level, number of click trains per minute, pulse number, and average inter-pulse interval (PI) per click train were all affected. The PI increased and exhibited a slight downward trend during the chase. The increase in PI indicated an increase in the inspection distance as the dolphin escaped. Thus, Irrawaddy dolphins may adapt their echolocation signals to stand out from ambient noise in the wild and to improve their search efforts in potentially risky situations. Appropriate management of the burst noise around the dolphins is important.

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