The importance of individual variation in the dynamics of animal collective movements

Abstract

Animal collective movements are a key example of a system where we aim to understand the link between two clearly defined levels of organization: the individual and the group. Initial models investigating collective movements produced coherent collective behaviours without the inclusion of individual variability. However, new individual-based models are, together with emerging empirical information, clearly demonstrating that within-group heterogeneity may strongly influence collective movement behaviour. Here we 1) review theempirical evidence for individual variation in animal collective movements, 2) explore how theoretical investigations have represented individual heterogeneity when modelling collective movements, and 3) present a model to show how within-group heterogeneity impact on the collective properties of the group. Our review underscores the need to consider variability at the level of the individual to improve our understanding of how individual decision rules lead to emergent movement patterns, and also to yield better quantitative predictions of collective behaviour.