Schools of fish and flocks of birds: their shape and internal structure by self-organization

Authored by Charlotte Hemelrijk, Hanno Hildenbrandt

Date Published: 2012

DOI: 10.1098/rsfs.2012.0025

Sponsors: Netherlands Organization for Scientific Research (NWO)

Platforms: No platforms listed

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

Models of self-organization have proved useful in revealing what processes may underlie characteristics of swarms. In this study, we review model-based explanations for aspects of the shape and internal structure of groups of fish and of birds travelling undisturbed (without predator threat). Our models attribute specific collective traits to locomotory properties. Fish slow down to avoid collisions and swim at a constant depth, whereas birds fly at low variability of speed and lose altitude during turning. In both the models of fish and birds, the `bearing angle' to the nearest neighbour emerges as a side-effect of the `blind angle' behind individuals and when group size becomes larger, temporary subgroups may increase the complexity of group shape and internal structure. We discuss evidence for model-based predictions and provide a list of new predictions to be tested empirically.

Tags

Individual-based model Decision-Making Emergent properties Animal groups Starling flocks 3-dimensional structure Sturnus-vulgaris Tail beat frequency Predators attack Prey-flock