Initiation and spread of escape waves within animal groups

Abstract

The exceptional reactivity of animal collectives to predatory attacks is thought to be due to rapid, but local, transfer of information between group members. These groups turn together in unison and produce escape waves. However, it is not clear how escape waves are created from local interactions, nor is it understood how these patterns are shaped by natural selection. By startling schools of fish with a simulated attack in an experimental arena, we demonstrate that changes in the direction and speed by a small percentage of individuals that detect the danger initiate an escape wave. This escape wave consists of a densely packed band of individuals that causes other school members to change direction. In the majority of cases this wave passes through the entire group. We use a simulation model to demonstrate that this mechanism can, through local interactions alone, produce arbitrarily large escape waves. In the model, when we set the group density to that seen in real fish schools, we find that the risk to the members at the edge of the group is roughly equal to the risk of those within the group. Our experiments and modelling results provide a plausible explanation for how escape waves propagate in Nature without centralised control.

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Cited by in corpus (10)

• Short-range interaction vs long-range correlation in bird flocks
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• Identifying differences in the rules of interaction between individuals in moving animal groups
• Escape path complexity and its context dependency in Pacific blue-eyes (Pseudomugil signifer)
• Signatures of criticality in turning avalanches of schooling fish
• Signal propagation and linear response in the delay Vicsek model
• Collective response to local perturbations: how to evade threats without losing coherence
• An Alignment-Free Explanation for Collective Predator Evasion in Moving Animal Groups
• Excess of Social Behavior Reduces the Capacity to Respond to Perturbations
• Individuals' Mobility May Promote Criticality in Animal Collective Decision-making