ABSTRACT
Recent developments in image analysis have made it possible to obtain kinetic data regarding how real organisms move, revealing dynamic internal structures within groups, such as topological distances, scale-free correlations and inherent noise. It has been suggested that the latter may play an essential role in collective motion. Here, we show how inherent noise driven by mutual anticipation can actively contribute to the establishment and maintenance of a robust swarm acting as one body. To this end, we compared a model based on the mutual anticipation of organisms with kinetic data collected from soldier crabs, Mictyris guinotae. In both the model and the real data, a swarm could be characterized as having a high density and a wide variety of polarization. Our model demonstrated that a swarm could enter and cross water only if the swarm were driven by inherent turbulence to become highly concentrated. We implemented an hourglass composed of crabs to illustrate regular oscillation, which could be mimicked by our model. Both our model and the kinetic data revealed a scale-free correlation in which the correlation function exhibited linear decay independent of swarm size. This model should prove widely applicable for the study of collective biological phenomena.
