Echolocation Clicks of Irrawaddy Dolphins ( Orcaella brevirostris ) During Foraging in the Bay of Brunei, Malaysia
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ORIGINAL PAPER
Echolocation Clicks of Irrawaddy Dolphins (Orcaella brevirostris) During Foraging in the Bay of Brunei, Malaysia Hairul Masrini Muhamad1 · Xiaomei Xu1 · Xuelei Zhang2 · Saifullah Arifin Jaaman3 · Azmi Marzuki Muda3 · Farah Dayana Haji Ismail3 · Nurlisa Azizul3 Received: 14 January 2020 / Revised: 1 March 2020 / Accepted: 11 March 2020 © Australian Acoustical Society 2020
Abstract The source parameters of Irrawaddy dolphins’ echolocation click in the Bay of Brunei were estimated. Analysis of eight parameters shows that the Irrawaddy dolphins produce broadband echolocation clicks with mean click duration of 21.1 ± 7.2 µs. The clicks had a mean peak-to-peak apparent source level (ASLpp ) of 201.2 ± 7.3 dB re 1 µPa (N 350), a mean peak frequency of 116.5 ± 15.2 kHz, a mean centroid frequency of 115.4 ± 13.9 kHz, − 3 dB bandwidth of 51.8 ± 17.7 kHz, and − 10 dB bandwidth of 100.9 ± 20.3 kHz. Foraging behaviour was characterized by the high movement of the animals in various directions with no obvious pattern and frequent deep dives. The source parameters of the Brunei Bay Irrawaddy dolphins’ clicks from the present study were compared to those of the populations in Bangladesh and Thailand. The apparent source level and frequency range of clicks for the population in Brunei Bay were wider than those of the population in Bangladesh and Thailand. The variations in the measured parameters might be due to environmental factors or behaviour related. Keywords Irrawaddy dolphin · Orcaella brevirostris · Bay of Brunei · Echolocation clicks · Source level · Peak frequency · Foraging
1 Introduction Dolphins possess a very sophisticated biosonar system that allows the animals to detect, identify, and catch prey [1, 2]. Researchers continue to describe dolphin’s acoustic properties both in captivity and in the wild. However, there is still more to investigate regarding the acoustic properties and the functions of dolphin emitted signals as they can vary within species, geographic regions, behavioural context, and environmental factors [3–7]. The acoustic repertoire of dolphins
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Xiaomei Xu [email protected]
1
Key Laboratory of Underwater Acoustic Communication and Marine Information Technology (Xiamen University), Ministry of Education, College of Ocean and Earth Sciences, Xiamen University, Xiang’an Campus, Xiamen 361102, Fujian, China
2
MNR Key Laboratory for Science and Engineering of Marine Ecosystem, First Institute of Oceanography (FIO), Ministry of Natural Resources (MNR), Qingdao 266061, China
3
Institute of Oceanography and Environment, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
can be divided into three primary categories: frequencymodulated whistles, clicks (broadband high frequency and narrowband high frequency), and burst pulse (bark, squawk, moan) sounds that being used in social and navigational contexts [8–12]. In echolocation, dolphins produce and listen to the echo sounds to gather information about their environment and potential prey. The sounds consist of s
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