Whistle characteristics of a newly recorded Indo‐Pacific humpback dolphin (Sousa chinensis) population in waters southwest of Hainan Island, China, differ from other humpback dolphin populations

Abstract

Indo‐Pacific humpback dolphins (Sousa chinensis) use whistles to communicate with their conspecifics. Little is known about the acoustic repertoire of Indo‐Pacific humpback dolphins in waters southwest of Hainan Island, a newly recorded population in 2014. In this study, whistles of Hainan humpback dolphin population were collected by using autonomous acoustic recorders. The fundamental frequencies and durations of whistles were in ranges of 0.71–21.35 kHz and 0.06–2.22 s, respectively. Significant intraspecific differences in duration and frequency of whistles were found between the Hainan population and the other geographically neighboring populations (in Chinese waters) or the population in Malaysia waters. Compared with other Sousa species, significant interspecific differences were also observed. Based on clustering analysis, the whistle parameters of neighboring populations were likely similar to each other. Significant differences were found between humpback dolphins in waters southwest of Hainan Island and those dolphins in the neighboring areas, supporting the hypothesis that this population may be independent. Ambient noise measurements in waters of Hainan Island, Zhanjiang, and Sanniang Bay showed that humpback dolphin populations may use whistles with longer duration, lower frequency, and fewer inflection points for more effective communication to adapt to a noisier environment.

Population distribution, connectivity and differentiation of Indo‐Pacific humpback dolphins in Chinese waters: Key baselines for improving conservation management

“…Dong et al (2019) showed that most duration and frequency parameters of whistles recorded from humpback dolphins in EZJ were significantly different from those recorded in SNB. Dong et al (2021) Evidence of the population differentiation of humpback dolphins in Chinese waters is also available from other behavioural aspects, such as sociality and habitat use strategy (Table 1). Liu et al (2021a) compared the group size data collected from three humpback dolphin populations in SWH, EZJ and SNB.…”

“…Dong et al (2019) showed that most duration and frequency parameters of whistles recorded from humpback dolphins in EZJ were significantly different from those recorded in SNB. Dong et al (2021) established a relatively large dataset and further demonstrated significant statistical differences in the duration and frequency parameters of humpback dolphin whistles between SWH, EZJ and SNB. Similarly, Yuan et al (2021) showed statistically significant differences in whistle parameters among humpback dolphins in EZJ, SNB and PRE.…”

“…Similarly, Yuan et al (2021) showed statistically significant differences in whistle parameters among humpback dolphins in EZJ, SNB and PRE. These findings supplement bioacoustic evidence to demonstrate the population differentiation mechanisms of geographical barriers.Overall, the interspecific and intraspecific variability in humpback dolphin sounds may reflect their dispersal capabilities, genetic divergence, geographical isolation and adaptation to ecological constraints(Dong et al, 2017;Dong et al, 2019;Dong et al, 2021;Yuan et al, 2021).…”

Research on whales, dolphins, and porpoises

“…Their findings suggested that these geographic variations in humpback dolphin whistles might be driven by both geographical barrier and local ambient noise, which were consistent with the findings reported by Dong et al . (2019, 2021b).…”

“…Therefore, characteristics of the underwater soundscape in cetacean habitats and effects of noise on them have been a research topic attracting increasing interest in recent decades (Weilgart 2007;Erbe et al 2016). In this volume, Dong et al (2021a) investigated temporal variation of the underwater soundscape in a tropical habitat of Indo-Pacific humpback dolphins. The authors observed a significant relationship between detection rates of anthropogenic sounds and dolphin sounds; however, fish detection rates showed no effect on dolphin detection rates.…”