10.6084/m9.figshare.5340580.v1 James E. Herbert-Read James E. Herbert-Read Emil Rosén Emil Rosén Alex Szorkovszky Alex Szorkovszky Christos C. Ioannou Christos C. Ioannou Björn Rogell Björn Rogell Andrea Perna Andrea Perna Indar W. Ramnarine Indar W. Ramnarine Alexander Kotrschal Alexander Kotrschal Niclas Kolm Niclas Kolm Jens Krause Jens Krause David J. T. Sumpter David J. T. Sumpter Supplementary Information from How predation shapes the social interaction rules of shoaling fish The Royal Society 2017 group living collective motion Poecilia reticulata collective behaviour interaction rules 2017-08-24 11:13:41 Journal contribution https://rs.figshare.com/articles/journal_contribution/Supplementary_Information_from_How_predation_shapes_the_social_interaction_rules_of_shoaling_fish/5340580 Predation is thought to shape the macroscopic properties of animal groups, making moving groups more cohesive and coordinated. Precisely how predation has shaped individuals' fine-scale social interactions in natural populations, however, is unknown. Using high-resolution tracking data of shoaling fish (<i>Poecilia reticulata</i>) from populations differing in natural predation pressure, we show how predation adapts individuals' social interaction rules. Fish originating from high predation environments formed larger, more cohesive, but not more polarized groups than fish from low predation environments. Using a new approach to detect the discrete points in time when individuals decide to update their movements based on the available social cues, we determine how these collective properties emerge from individuals' microscopic social interactions. We first confirm predictions that predation shapes the attraction–repulsion dynamic of these fish, reducing the critical distance at which neighbours move apart, or come back together. While we find strong evidence that fish align with their near neighbours, we do not find that predation shapes the strength or likelihood of these alignment tendencies. We also find that predation sharpens individuals' acceleration and deceleration responses, implying key perceptual and energetic differences associated with how individuals move in different predation regimes. Our results reveal how predation can shape the social interactions of individuals in groups, ultimately driving differences in groups' collective behaviour.