Avalanche dynamics of zebrafish schools: Unveiling self-organization and phase transitions

Collective behavior in animal groups exhibits intriguing dynamics that can be analyzed through the lens of self-organized criticality. In this context, we analyze behavioral cascades in zebrafish (Danio rerio) groups of varying sizes within controlled tank environments. Through experimental observations and data analysis, we unveil scale-free signatures reminiscent of self-organized critical processes in the collective movement of zebrafish. Notably, as fish density varies, we observe a dynamic phase transition: at low densities, coordinated and highly polarized movement dominates, while at high densities, the group fractures into uncorrelated domains. These findings shed light on the complex dynamics of collective behavior in fish groups and provide valuable insights into the responses of individuals to environmental stimuli. Moreover, the observed phase transition highlights the sensitivity of zebrafish behavior to changes in population density, which has implications for understanding collective behavior in various contexts, from ecological systems to preclinical studies. Finally, we compare our findings with the known results of avalanche analyses of collective motion and neuronal activity. All follow the same power law, indicating a possible universality in one parameter of avalanche processes.