Apparent source levels and active communication space of whistles of free-ranging Indo-Pacific humpback dolphins ( Sousa chinensis ) in the Pearl River Estuary and Beibu Gulf, China

PeerJ

article

Zhi-Tao Wang¹  Whitlow W.L. Au³  Luke Rendell⁵  Ke-Xiong Wang¹  Hai-Ping Wu⁶  Yu-Ping Wu⁷  Jian-Chang Liu⁸  Guo-Qin Duan⁹  Han-Jiang Cao⁹  Ding Wang¹ 

[1] The Key Laboratory of Aquatic Biodiversity and Conservation of the Chinese Academy of Sciences, Institute of Hydrobiology of the Chinese Academy of Sciences;University of Chinese Academy of Sciences;Marine Mammal Research Program, Hawaii Institute of Marine Biology, University of Hawaii;Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University;Sea Mammal Research Unit, School of Biology, University of St. Andrews;School of Marine Sciences, Qinzhou University;School of Marine Sciences, Sun Yat-Sen University;Transport Planning and Research Institute, Ministry of Transport;Hongkong-Zhuhai-Macao Bridge Authority

关键词: Active communication space;    Pearl River Estuary;    Sound propagation model;    Whistles;    Indo-Pacific Humpback dolphins;    Hydrophone arrays;    Beibu Gulf;    Apparent source level;    Sousa chinensis;   

DOI  :  10.7717/peerj.1695

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Background. Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats.Methods. We used a two-dimensional cross-shaped hydrophone array system to record the whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in shallow-water environments of the Pearl River Estuary (PRE) and Beibu Gulf (BG), China. Using hyperbolic position fixing, which exploits time differences of arrival of a signal between pairs of hydrophone receivers, we obtained source location estimates for whistles with good signal-to-noise ratio (SNR ≥10 dB) and not polluted by other sounds and back-calculated their apparent source levels (ASL). Combining with the masking levels (including simultaneous noise levels, masking tonal threshold, and the Sousa auditory threshold) and the custom made site-specific sound propagation models, we further estimated their active communication space (ACS).Results. Humpback dolphins produced whistles with average root-mean-square ASL of 138.5 ± 6.8 (mean ± standard deviation) and 137.2 ± 7.0 dB re 1 µPa in PRE (N = 33) and BG (N = 209), respectively. We found statistically significant differences in ASLs among different whistle contour types. The mean and maximum ACS of whistles were estimated to be 14.7 ± 2.6 (median ± quartile deviation) and 17.1± 3.5 m in PRE, and 34.2 ± 9.5 and 43.5 ± 12.2 m in BG. Using just the auditory threshold as the masking level produced the mean and maximum ACSat of 24.3 ± 4.8 and 35.7 ± 4.6 m for PRE, and 60.7 ± 18.1 and 74.3 ± 25.3 m for BG. The small ACSs were due to the high ambient noise level. Significant differences in ACSs were also observed among different whistle contour types.Discussion. Besides shedding some light for evaluating appropriate noise exposure levels and information for the regulation of underwater acoustic pollution, these baseline data can also be used for aiding the passive acoustic monitoring of dolphin populations, defining the boundaries of separate groups in a more biologically meaningful way during field surveys, and guiding the appropriate approach distance for local dolphin-watching boats and research boat during focal group following.

【 授权许可】

CC BY