A miniature biomimetic sonar and movement tag to study the biotic environment and predator-prey interactions in aquatic animals

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Goulet, Pauline, Guinet, Christophe, Swift, Rene, Madsen, Peter, S, Johnson, Mark
• Other Authors: Sea Mammal Research Unit University of St Andrews (SMRU), School of Biology University of St Andrews, University of St Andrews Scotland -University of St Andrews Scotland -Natural Environment Research Council (NERC), Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Aarhus University Aarhus
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: Prey field mapping; Fisheries sonar; Foraging ecology; Elephant seal; Predator-prey interactions; Biologging; [SDE]Environmental Sciences; Elephant Seal; Southern Elephant Seal; toothed whales
• Online Access: https://hal.science/hal-02165843; https://doi.org/10.1016/j.dsr.2019.04.007

International audience How predators find, select and capture prey is central to understanding trophic cascades and ecosystem structure.But despite advances in biologging technology, obtaining in situ observations of organisms and their interactionsremains challenging in the marine environment. For some species of toothed whales, echoes fromorganisms insonified by echolocation clicks and recorded by sound logging tags have provided a fine-scale viewof prey density, and predator and prey behaviour during capture attempts, but such information is not availablefor marine predators that do not echolocate. Here the development and performance of a miniature biomimeticsonar and movement tag capable of acquiring similar data from non-echolocating marine predators is reported.The tag, weighing 200 g in air, records wide bandwidth sonar data at up to 50 pings a second synchronously withfast-sampling sensors for depth, acceleration, magnetic field and GPS. This sensor suite enables biotic conditionsand predator behaviour to be related to geographic location over long-duration foraging trips by apex marinepredators. The sonar operates at 1.5 MHz with a 3.4° beamwidth and a source level of 190 dB re 1 μPa at 1 m.Sonar recordings from a trial deployment of the tag on a southern elephant seal contained frequent targetscorresponding to small organisms up to 6m ahead of the tagged animal. Synchronously sampled movement dataallowed interpretation of whether the seal attempted to capture organisms that it approached closely while thehigh sonar ping rate revealed attempts by prey to escape. Results from this trial demonstrate the ability of the tagto quantify the biotic environment and to track individual prey captures, providing fine-scale information onpredator-prey interactions which has been difficult to obtain from non-echolocating marine animals.