Whistle signal variations among three Indo‐Pacific humpback dolphin populations in the South China Sea: a combined effect of the Qiongzhou Strait's geographical barrier function and local ambient noise?

• Published in: Integrative zoology 2021-07, Vol.16 (4), p.499-511
• Main Authors: YUAN, Jing, WANG, Zhitao, DUAN, Pengxiang, XIAO, Yousheng, ZHANG, Hongke, HUANG, Zhixiong, ZHOU, Ruichun, WEN, Hua, WANG, Kexiong, WANG, Ding
• Format: Article
• Language: English
• Subjects: Acoustics; Ambient noise; Aquatic mammals; Estuaries; Estuarine dynamics; Generalized linear models; geographic difference; geographical barrier; Geographical variations; Geography; Indo‐Pacific humpback dolphins; Marine mammals; Noise; Noise pollution; Parameters; Population number; Sousa chinensis; Species extinction; Straits; Vocalization behavior; whistle
• ISSN: 1749-4877; 1749-4869; 1749-4877
• DOI: 10.1111/1749-4877.12531

Geographic variations in the dolphin whistles could be useful in assessing association and isolation among populations. Whistle of free‐ranging Indo‐Pacific humpback dolphins (Sousa chinensis) among the Pearl River Estuary (PRE), Leizhou Bei (LZB) and Sanniang Bay (SNB) populations were investigated. A total of 2850 whistles with legible fundamental contour were extracted and 15 acoustic parameters were measured. Contrary to SNB, PRE and LZB had the same relative proportion of tonal type compositions with flat and sine representing the most frequent types. The generalized linear model analysis showed significant acoustic difference among populations and tonal types. All frequency parameters in SNB were significantly higher than those in PRE and LZB, where no significant variation was observed in most of the parameters either at the population level or within each tonal type. Canonical discriminant functions analysis showed a smaller difference between PRE and LZB than between PRE and SNB and between LZB and SNB. Compared with previous recordings, recent recordings demonstrated a consistent pattern of becoming higher in whistle frequency parameters in both LZB and SNB populations, suggesting that noise pollution in LZB and SNB increasing with time according to the acoustic niche hypothesis. Dolphin whistle's geographic variations could be shaped by the combined function of the geographical barrier function of the Qiongzhou strait and local ambient noise. Considering the isolated condition and the relatively smaller population size of the humpback dolphin in the SNB, more effective and proactive conservation actions should be taken to prevent the extinction of small populations. Whistle of free‐ranging Indo‐Pacific humpback dolphins (Sousa chinensis) among the Pearl River Estuary (PRE), Leizhou Bay (LZB) and Sanniang Bay (SNB) populations were investigated. Smaller difference between PRE and LZB than between PRE and SNB and between LZB and SNB were observed. These geographic variations in humpback dolphin whistle signals could be shaped by the combined function of the geographical barrier function of the Qiongzhou strait and local ambient noise. Considering the isolated condition and the relatively smaller population size of the humpback dolphin in the SNB, more effective and proactive conservation actions should be taken to protect humpback dolphins.