Incorporating the Confusion Effect into the Simulated Evolution of Crowded Selfish Herds

Regarding collective animal behaviour, a gap has long existed between perspectives from the anti-predator benefit and the evolutionary dynamic. On the one hand, studies on natural swarm intelligence rarely consider how this advantage keeps stable in evolution. On the other hand, evolutionary theories used to neglect the change of absolute fitness at the group level. Nevertheless, social profits are not evenly distributed to individuals. An anti-predator function, therefore, may affect the relative fitness and shape the behavioural evolution in an animal population. To investigate this issue, we adopted the crowded-selfish-herd model with minimum modification to include the confusion effect, a common anti-predator function of prey crowds. Three arguments are proposed from our simulations. First, the negative correlation between the effect strength and the emergent group density shows the confusion effect is restrained by intraspecific competition. Secondly, highly coordinated movements are primary stable states, which geometry is moulded by the degree of the confusion effect. Lastly, a strong confusion effect promotes a branch of stable states where selfish herds exercise as swarms of millipedes. These findings hint that the geometry of collective patterns is possible to identify the existence of confusion effects in nature.