Summary The collective motion of swarms depends on adaptations at the individual level. We explored these and their effects on swarm formation and maintenance in locusts. The walking kinematics of individual insects were monitored under laboratory settings, before, as well as during collective motion in a group, and again after separation from the group. It was found that taking part in collective motion induced in the individual unique behavioral kinematics, suggesting the existence of a distinct behavioral mode that we term a “collective-motion-state.” This state, characterized by behavioral adaptation to the social context, is long lasting, not induced by crowding per se, but only by experiencing collective motion. Utilizing computational models, we show that this adaptability increases the robustness of the swarm. Overall, our findings suggest that collective motion is not only an emergent property of the group but also depends on a behavioral mode, rooted in endogenous mechanisms of the individual.

AbstractCollective motion is an important biological phenomenon, ubiquitous among different organisms. Locusts are a quintessential example of collective motion: while displaying a minimal level of cooperation between individuals, swarms of millions are highly robust and persistent. Using desert locusts in a series of carefully controlled laboratory experiments, we show that locust coordinated marching induces a distinct behavioral mode in the individual that we term a “collective-motion-state”. Importantly, this state is not induced by aggregation or crowding per-se, but only following collective motion. It is manifested in specific walking behavior kinematics and has a lasting effect. Simulations confirm that the collective-motion-state provides an individual-based mechanism, which increases the robustness and stability of swarms in the presence of fluctuations. Overall, our findings suggest that collective-motion is more than an emergent property of the group, but a specific behavioral mode that is rooted in endogenous biological mechanisms of the individual.