Abstract
Dolphins produce narrowband and frequency modulated sounds called whistles during a variety of behavioral contexts. Dolphin species vary in their whistle contour composition, frequency range, modulation, and duration, and these differences can be useful in their identification. Here, we compare the whistle contours of two sympatric dolphin species at La Paz Bay, Gulf of California, the Eastern Tropical Pacific bottlenose dolphin, and the long-beaked common dolphin. Dolphins were recorded (7 h and 1 min recording effort) from the research vessel with the engine off using an over-the-side hydrophone and a broadband recording system. A total of 666 high quality whistles (bottlenose dolphin, n = 415; long-beaked common dolphin, n = 251) were analyzed. A Random Forest Analysis identified duration, ending frequency, and maximum frequency as the most important variables that distinguish the two dolphin species. The most common whistle contour types of bottlenose dolphins were sine and convex, while the long-beaked common dolphins produced mainly upsweep and concave whistles. The results showed that bottlenose dolphins and long-beaked common dolphins differ in their whistle variables and contours facilitating their identification in future passive acoustic studies.
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Data availability
The data presented in this study are available on request from the corresponding author.
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Acknowledgements
The authors are grateful to Citlali Cuevas, Mario Márquez Segovia and Minerva Valerio Conchas (Programa de Investigación en Mamíferos Marinos-Universidad Autónoma de Baja California Sur) for their help during the data collection. A special thanks to the Secretariat of Environment and Natural Resources of Mexico (SEMARNAT) for providing the Scientific Research Permit [Permit SGPA/DGVS/00657/21] to conduct fieldwork activities.
Funding
This study is part of the PhD program of Simone Antichi conducted at the UABCS (Universidad Autónoma de Baja California Sur). The PhD scholarship to Simone Antichi is provided by Consejo Nacional de Humanidades, Ciencias y Tecnologías (Conahcyt) (Grant Number 759498). The boat-based surveys were financed by internal funds of the UABCS.
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All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Simone Antichi, Manali Rege‑Colt, Maia Austin, Óscar Carlón-Beltrán, Sergio Martínez-Aguilar and Lorena Viloria-Gómora. The first draft of the manuscript was written by Simone Antichi, Manali Rege‑Colt and Laura May-Collado and all authors contributed to edit the manuscript. All authors read and approved the final manuscript.
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Antichi, S., Rege‑Colt, M., Austin, M. et al. Whistle structure variation between two sympatric dolphin species in the Gulf of California. Hydrobiologia (2024). https://doi.org/10.1007/s10750-024-05675-3
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DOI: https://doi.org/10.1007/s10750-024-05675-3