Effect of inertia on the evasion and pursuit dynamics of prey swarms and the emergence of an optimal mass ratio for the predator-prey arms race

TL;DR

This paper presents a theoretical model showing how inertia influences prey swarm survival and reveals an optimal predator-prey mass ratio that balances pursuit and escape, mirroring natural observations.

Contribution

It introduces a novel theoretical framework linking inertia and mass ratios to predator-prey dynamics and survival outcomes.

Findings

Diverse escape patterns emerge with varying masses.

A transition from non-survival to survival occurs with increasing predator mass.

An optimal predator-prey mass ratio enhances predation efficiency.

Abstract

We show, based on a theoretical model, how inertia plays a pivotal role in the survival dynamics of a prey swarm while chased by a predator. With the varying mass of the prey and predator, diverse escape patterns emerge, such as circling, chasing, maneuvering, dividing into subgroups, and merging into a unitary group, similar to the escape trajectories observed in nature. Moreover, we find a transition from non-survival to survival of the prey swarm with increasing predator mass. The transition regime is also sensitive to the variation in prey mass. Further, the analysis of the prey group survival as a function of predator-to-prey mass ratio unveils the existence of three distinct regimes: (i) frequent chase and capture leading to the non-survival of the prey swarm, (ii) an intermediate regime where competition between pursuit and capture occurs, resembling an arms race, and (iii) the survival regime without the capture of prey. Interestingly, our study demonstrates the existence of a favourable predator-prey mass ratio for efficient predation, which corroborates with the field studies.