Avoiding ant jams

Abstract

Behavior Traffic congestion is a daily challenge for humans pursuing individual objectives. Ants also live, work, and commute in crowded circumstances but avoid gridlock. Poisonnier et al. analyzed how the collective foraging activity of Argentine ants never suffers congestion. Ant trails to food sources characteristically show bidirectional movement, which would appear to be vulnerable to collisions. However, why collisions are infrequent is not well understood. Using different sizes of lab colonies, the authors built bridges of different widths between the ants and food. Surprisingly, it was not strict discipline, such as forming lanes, that prevented holdups; rather, individual ants constantly adjusted their behavior to prevent jams. First they avoided leaving the nest at high traffic density; then they restrained themselves from social contact, information sharing, and making U-turns; and finally, they adjusted their speed according to individual perceptions of local crowding. Unlike humans, ants can regulate individual behavior to benefit the smooth functioning of the whole population. Maybe we can program driverless cars to perform as well as ants. eLife 8 , e48945 (2019).