Predator confusion is sufficient to evolve swarming behavior

TL;DR

This study demonstrates through an evolutionary model that predator confusion alone can drive the development of swarming behavior in prey and influence predator visual system evolution, affecting predator-prey dynamics.

Contribution

It provides evidence that predator confusion is sufficient to promote prey swarming and shape predator sensory adaptations in an evolutionary context.

Findings

Predator confusion can lead to the evolution of prey swarming behavior.

Swarming influences the structure of predator visual systems, favoring frontal, high-resolution vision.

Prey swarming alters the predator's functional response curve with increasing prey density.

Abstract

Swarming behaviors in animals have been extensively studied due to their implications for the evolution of cooperation, social cognition, and predator-prey dynamics. An important goal of these studies is discerning which evolutionary pressures favor the formation of swarms. One hypothesis is that swarms arise because the presence of multiple moving prey in swarms causes confusion for attacking predators, but it remains unclear how important this selective force is. Using an evolutionary model of a predator-prey system, we show that predator confusion provides a sufficient selection pressure to evolve swarming behavior in prey. Furthermore, we demonstrate that the evolutionary effect of predator confusion on prey could in turn exert pressure on the structure of the predator's visual field, favoring the frontally oriented, high-resolution visual systems commonly observed in predators that feed on swarming animals. Finally, we provide evidence that when prey evolve swarming in response to predator confusion, there is a change in the shape of the functional response curve describing the predator's consumption rate as prey density increases. Thus, we show that a relatively simple perceptual constraint--predator confusion--could have pervasive evolutionary effects on prey behavior, predator sensory mechanisms, and the ecological interactions between predators and prey.