Collective dynamics and model verification: Connecting kinetic modeling to data

Moving in the crowd : Ants hold the key to traffic chaos

Audrey Dussutour

University of Toulouse III, CNRS

Many species of group-living animals move in groups of tens to thousands individuals. These groups can sometimes form collective spatio-temporal structures that can reach a high level of complexity. The challenge meet by these groups is twofold. First, individuals within these groups have to coordinate their movements so that the group as a whole keeps its cohesion and progress smoothly. Second, they have to perform efficient avoidance maneuvers to avoid bumping into each other, which would considerably slow down their movement. The research of our team during the last years has addressed these aspects of collective movements in ants. Collective movements in ants take the form of fluid-like bidirectional movement along foraging trails. However, ants do not behave as fluid-like particles bumping incessantly into each other. In fact, contrary to what should be expected if it were the case, we were able to show that in ants there is little reduction in ant speed with increasing density of individuals on foraging trails: the flow of ants does not decrease even when the density of individuals on the trails reaches high values. Traffic organization due to ants moving in opposite direction obeying priority rules may provide an explanation to this result. We tested these hypotheses in various ants through both an experimental and modeling approach.