Perceived risk determines spatial position in fish shoals through altered rules of interaction

TL;DR

This study shows that perceived risk influences fish shoal structure by altering local interaction rules, leading risk-sensitive individuals to occupy central positions and exhibit distinct movement behaviors, validated by a machine learning classifier.

Contribution

It reveals how heterogeneity in risk perception affects spatial positioning and interaction rules within fish groups, advancing understanding of collective animal behavior.

Findings

Risk perception influences fish spatial positioning within shoals.

Risk-sensitive fish exhibit greater coordination and different movement dynamics.

A machine learning classifier accurately identifies subgroup membership based on behavior.

Abstract

Risk perception plays a key role in shaping the collective behavior of moving animal groups, yet the effects of variation in perceived risk within groups is unknown. Here, we merge two subgroups of fish with different levels of perceived risk, manipulated through habituation to the experimental arena, and quantitatively analyze their movement. Fish with heightened risk perception tend to occupy more central positions within the group, consistent with the selfish herd hypothesis. This behavior appears to be driven by adjusted local interactions with nearby individuals. Compared to more habituated fish, these individuals also exhibit greater coordination, shorter burst-and-coast dynamics, more efficient information transmission, and a stronger tendency to adopt follower roles. To validate the findings, we develop a machine learning tool that successfully classifies the subgroup identity of individual fish. Our study demonstrates how differences in local-scale inter-individual interactions can drive spatial assortment within groups, based on heterogeneity in the perception of risk.