Survival chances of a prey swarm: selfish runaway versus cooperative interaction

Cohesive group formation has been observed in diverse species, for example, flock of birds, school of fishes, herd of zebras, huddle of penguins to name a few. In nature, swarming behaviour has generally been found in search of food, for breeding, or to avoid predators etc. However, swarming could also thought to be unfavourable for preys as the predator could easily track and attack the whole group. Here, we investigate the effect of cooperative interaction within a prey group based on a simple theoretical prey-predator model framework incorporating short range repulsion and long range attraction between preys. Moreover, the range of interaction of preys, as in real scenario, may be limited due to their sensitivity, vision, age, or even physical structure; hence, in our model, we consider that each prey interacts with other neighbouring preys within a certain range of interaction radius. Our analysis shows that varying range of interaction vastly influences the trajectory of preys when chased by a predator and also strongly affects the survival probability of the prey group. Interestingly, we find that the survival of number of preys increases within an intermediate regime of interaction radius. These findings could also be qualitatively mapped with observations in nature.