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Applied Mathematics Colloquium

Friday, December 7, 11:30 am
Cullimore Lecture Hall II
New Jersey Institute of Technology

Collective Motion and Decision-Making in Animal Groups

Iain Couzin

Department of Ecology and Evolutionary Biology

Princeton University

Princeton, NJ

Abstract

Animal groups such as bird flocks, insect swarms and fish schools are spectacular, ecologically important and sometimes devastating features of the biology of various species. Outbreaks of the desert locust, for example, can invade approximately one-fifth of the Earth's land surface and are estimated to affect the livelihood of one in ten people on the planet. Using a combined theoretical and experimental approach involving insect and vertebrate groups, I will address how, and why, individuals move in unison and investigate the principles of information transfer in these groups, particularly focusing on leadership and collective consensus decision-making. For very large animal groups, despite huge differences in the size and cognitive abilities of group members, recent models from theoretical physics ("self-propelled particle," SPP, models) have suggested that general principles underlie collective motion. Such models demonstrate that group-level properties may be largely independent of the types of animals involved. I shall present recent experimental work on locusts that validates some of the predictions of simple mechanistic models, including a density-dependent transition from disordered to ordered motion. Details of the mechanism by which individuals interact will also be revealed using nerve manipulations and field experiments, demonstrating that animals within these huge mobile groups are in effect on a "forced march" driven by cannibalism. These results will be discussed in the context of the evolution of functional complexity and pattern formation in biological systems.