Emergent Dynamics of Active Collective Swaying Synchronization

Most flying fox species roost in large colonies on tree branches. In Pteropus colonies, hundreds of individuals sway collectively when perched, producing group oscillations. A colony of bats hangs collectively from tree branches, forming an organized spatial distribution throughout the canopy within natural roosting habitats. We studied the dynamics of this swaying synchrony using systematic video recordings of roosting bats. Individual trajectories were extracted to measure sway amplitude, phase, and frequency across animals sharing a branch. We observed transitions from incoherent movement to collective synchronization with external wind force, where individuals locked their sway phases within a narrow frequency. To explain this behavior, we analyzed the dynamics of coupling flexible branch dynamics with bats as active oscillators. The active collective swaying in bats is an emergent synchronization phenomenon on flexible substrates, expanding the understanding of collective behavior in animals and offering analogies for active matter and swarm robotics.