Fish shoals resemble a stochastic excitable system driven by environmental perturbations

Abstract Groups of animals can perform highly coordinated collective behaviours that confer benefits to the participating individuals by facilitating social information exchange and protection from predators 1 . Some these characteristics could arise when groups operate at critical points between two structurally functionally different states, leading maximal responsiveness external stimuli effective propagation 2,3 It has been proposed animal constitute examples self-organized systems criticality ; however, direct empirical evidence this hypothesis—in particular in wild—is mostly absent. Here we show conspicuous, repetitive rhythmic dive cascades produced many thousands freshwater fish under high predation risk resemble a stochastic excitable system driven environmental perturbations. Together with results an agent-based model system, suggests shoals might point state individual diving activity low overall activity. We best fitting model, which is located point, allows about perturbations—such as predator attacks—to propagate most effectively through shoal. Our suggest be plausible principle distributed processing large collectives.