How predation shapes the social interaction rules of shoaling fish

James E Herbert-Read, Emil Rosén, Alex Szorkovsky, Christos Ioannou, Bjorn Rogell, Andrea Perna, Indar Ramnarine, Alexander Kotrschal, Niclas Kolm, Jens Krause, David J.T. Sumpter

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Predation is thought to shape the macroscopic properties of animal groups,making moving groups more cohesive and coordinated. Precisely, howpredation has shaped individuals’ fine-scale social interactions in naturalpopulations, however, is unknown. Using high-resolution tracking data ofshoaling fish (Poecilia reticulata) frompopulations differing in natural predationpressure, we show how predation adapts individuals’ social interaction rules.Fish originating from high predation environments formed larger, morecohesive, but not more polarized groups than fish fromlowpredation environments.Using a new approach to detect the discrete points in time whenindividuals decide to update their movements based on the available socialcues, we determine how these collective properties emerge from individuals’microscopic social interactions. We first confirm predictions that predationshapes the attraction–repulsion dynamic of these fish, reducing the critical distanceat which neighbours move apart, or come back together. While we findstrong evidence that fish align with their near neighbours, we do not find thatpredation shapes the strength or likelihood of these alignment tendencies.We also find that predation sharpens individuals’ acceleration and decelerationresponses, implying key perceptual and energetic differences associatedwith how individuals move in different predation regimes. Our resultsreveal how predation can shape the social interactions of individuals ingroups, ultimately driving differences in groups’ collective behaviour.
© 2017, The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.
Original languageEnglish
JournalProceedings of The Royal Society B Biological Sciences
Publication statusPublished - 30 Aug 2017

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