Collective Behavior under Environmental Perturbations*

A wide range of animal species including birds, fish, and insects show complex, self-organized collective behavior in the wild. The nature of this collective behavior and its distinction from the aggregate behavior of individuals has been the subject of experimental and theoretical research for decades. However, it remains largely unknown how these collective systems respond to ubiquitous environmental perturbations such as currents, wind gusts, or sound or light signals. We have used laboratory experiments on Chironomus riparius, a midge species that predictably forms collective mating swarms, to investigate the response of swarms to perturbations that mimic expected environmental conditions in a well-controlled way. To do this, we used a multi-camera setup to record three-dimensional information about trajectories, velocities and accelerations of all individual midges in the swarm. We then characterize the individual and swarm responses to environmental perturbations using statistical and topological analysis.