Variation in foraging activity influences area-restricted search behaviour by bottlenose dolphins

Oihane Fernandez Betelu* (Corresponding Author), Virginia Iorio-Merlo, Isla Graham, Barbara Cheney, Simone Prentice, Xi Cheng, Paul Thompson

*Corresponding author for this work

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Area-restricted search (ARS) behaviour is commonly used to characterise spatio-temporal variation in foraging activity of predators, but evidence of the drivers underlying this behaviour in marine systems is sparse. Advances in underwater sound recording techniques and automated processing of acoustic data now provide opportunities to investigate these questions where species use different vocalisations when encountering prey. Here, we used passive acoustics to investigate drivers of ARS behaviour in a population of dolphins, to determine if residency in key foraging areas increased following encounters with prey. Analyses were based on two independent proxies of foraging: echolocation buzzes (widely used as foraging proxies), and bray calls (vocalizations linked to salmon predation attempts). Echolocation buzzes were extracted from echolocation data loggers and bray calls from broadband recordings by a convolutional neural network (CNN). We found a strong positive relationship between the duration of encounters and the frequency of both foraging proxies, supporting the theory that bottlenose dolphins engage in ARS behaviour in response to higher prey encounter rates. This study provides empirical evidence for one driver of ARS behaviour and demonstrates the potential for applying passive acoustic monitoring in combination with deep learning-based techniques to investigate the behaviour of vocal animals.
Original languageEnglish
Article number221613
Number of pages9
JournalRoyal Society Open Science
Issue number6
Early online date14 Jun 2023
Publication statusPublished - 14 Jun 2023

Bibliographical note

Open Access via the Royal Society Agreement

Beatrice Offshore Wind Ltd COWRIE Department of Energy & Climate Change, Scottish Government Fundación la Caixa (becas Posgrado, 2015) Marine Mammal Monitoring Programme (MMMP) Marine Scotland Science Moray Offshore Wind Farm (East) Ltd NatureScot
This project was made possible through the integration of O.F.B.'s PhD into a broader NatureScot and joint industry funded Marine Mammal Monitoring Programme (MMMP) that supports statutory monitoring of the Moray Firth SAC and offshore windfarm construction. We thank NatureScot, Marine Scotland Science, Beatrice Offshore Wind Ltd, Moray Offshore Wind Farm (East) Ltd, Department of Energy & Climate Change, Scottish Government, Oil & Gas UK and COWRIE for contributing funds or equipment to the MMMP. O.F.B. was funded through a studentship from the Fundación ‘la Caixa’ (Becas Posgrado, 2015). I.M.G., B.J.C. and P.M.T. were core funded by the University of Aberdeen but with salary support for the period of this study though contract to MMMP. V.I.M. and S.M.P. were funded through the MMMP. R.X.C. was core funded by Leibniz Institute for Zoo and Wildlife Research (IZW).

The authors gratefully acknowledge the support of the Maxwell High Performance Computing Cluster, funded by the University of Aberdeen, during the development of DOLPHIN-SPOT. We would also like to thank Claudia Aparicio Estaella for her help during the validation of the automatic detector. We acknowledge Bill Ruck, Moray First Marine and colleagues from the University of Aberdeen for assistance with the data collection and anonymous reviewers for comments that helped improve the manuscript.


  • Area-restricted search behaviour
  • Echolocation buzzes
  • Bray calls
  • Bottlenose dolphins
  • Machine learning
  • Passive acoustics


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