In the Chinese river dolphin, the baiji ( Lipotes vexillifer), whistles are thought to be the only communicative sounds produced by the species ( Wang, Wenxiang & Zhifan, 1995 Wang, Wang & Akamatsu, 1999 Wang et al., 2006 Xiao & Jing, 1989). More recently, studies have prioritized the characterization of echolocation ( Jensen et al., 2013 Sugimatsu et al., 2017), thus the role of other Ganges dolphin’s sounds remain poorly understood to this date. Other than visualizing spectrograms, no acoustic information was extracted from these sounds.

Mizue, Nishiwaki & Takemura (1971) recorded captive Ganges River dolphins ( Platanista gangetica) and reported three types of communication sounds: bursts, whistles, twittering and “stratiform” sounds. Uncovering the context in which these signals are produced may help understand the social structure of this species and contribute to our understanding of the evolution of acoustic communication in whales.Ĭompared to their marine counterparts, sounds produced by river dolphins and their role in communication remain understudied. Furthermore, the calls described here are similar in acoustic structure to those produced by social delphinids, such as orcas and pilot whales. Our findings show that the acoustic repertoire of river dolphins is far from simple. The most common types were emitted when calves were present suggesting a key role in mother-calf communication. Using a critical similarity value of 96%, frequency contours were categorized into 237 sound-types. These contours were analyzed using an adaptive resonance theory neural network combined with dynamic time-warping (ARTwarp). We analysed frequency contours of 727 signals (sampled at 10 ms temporal resolution). In this study, we described the acoustic repertoire of this newly discovered species in concert with their behaviour.

The recent discovery of the Araguaian river dolphin ( Inia araguaiaensis) highlights how little we know about the diversity and biology of river dolphins. The newly described Araguaian river dolphins, Inia araguaiaensis (Cetartiodactyla, Iniidae), produce a diverse repertoire of acoustic signals. Cite this article Melo-Santos G, Figueiredo Rodrigues AL, Tardin RH, de Sá Maciel I, Marmontel M, Da Silva ML, May-Collado LJ.

For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited. Licence This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. 9 Department of Biology, University of Vermont, Burlington, VT, United States of America DOI 10.7717/peerj.6670 Published Accepted Received Academic Editor Jose Maria Cardoso da Silva Subject Areas Animal Behavior, Biodiversity, Ecology, Zoology, Freshwater Biology Keywords Boto, Behavior, Acoustic communication, Mother-calf pairs, Non-linear phenomena Copyright © 2019 Melo-Santos et al.

River dolphin sounds