A Balanced Mixture of Antagonistic Pressures Promotes the Evolution of Parallel Movement

Interaction Rules Supporting Effective Flocking Behavior

Several simulation models have demonstrated how flocking behavior emerges from the interaction among individuals that react to the relative orientation of their neighbors based on simple rules. However, the precise nature of these rules and the relationship between the characteristics of the rules and the efficacy of the resulting collective behavior are unknown. In this article, we analyze the effect of the strength with which individuals react to the orientation of neighbors located in different sectors of their visual fields and the benefit that could be obtained by using control rules that are more elaborate than those normally used. Our results demonstrate that considering only neighbors located on the frontal side of the visual field permits an increase in the aggregation level of the swarm. Using more complex rules and/or additional sensory information does not lead to better performance.

Confined System Analysis of a Predator-Prey Minimalistic Model

In nature exists a properly defined food chain- an order of hunting and getting hunted. One such hunter-hunted pair is considered in this context and coordinated escape manoeuvres in response to predation is studied in case of a rarely examined confined system. Both the predator agent and prey agents are considered to be self-propelled particles moving in a viscous fluid. The state of motility when alive and passivity on death has been accounted for. A novel individual-based combination of Vicsek model and Boids flocking model is used for defining the self-propelling action and inter-agent interactions. The regimes observed at differing levels of co-ordination segregated by quantification of global order parameter are found to be in agreement with the extant literature. This study strives to understand the penalty on the collective motion due to the restraints employed by the rigid walls of the confinement and the predator’s hunting tactics. The success of any escape manoeuvre is dependent on the rate of information transfer and the strength of the agitation at the source of the manoeuvre. The rate of information transfer is studied as a function of co-ordination and the size of the influence zone and the source strength is studied as a function of escape acceleration activated on the agitated prey. The role of these factors in affecting survival rate of prey is given due coverage.

Collective Motion as an Ultimate Effect in Crowded Selfish Herds

The selfish herd hypothesis explains how social prey can assemble cohesive groups for maximising individual fitness. However, previous models often abstracted away the physical manifestation of the focal animals such that the influence of getting stuck in a crowded herd on individual adaptation was less intensively investigated. Here, we propose an evolutionary model to simulate the adaptation of egoistic social prey to predation given that individual mobility is strictly restrained by the presence of other conspecifics. In our simulated evolutionary races, agents were set to either be confined by neighbours or move to empty cells on the lattice, and the behavioural traits of those less exposed were selected and inherited. Our analyses show that under this crowded environment, cohesive and steady herds were consistently replaced by morphing and moving aggregates via the attempt of border agents to share predation risk with the inner members. This kind of collective motion emerges purely from the competition among selfish individuals regardless of any group benefit. Our findings reveal that including the crowding effect with the selfish herd scenario permits additional diversity in the predicted outcomes and imply that a wider set of collective animal behaviours are explainable purely by individual-level selection.