Dynamics of dominance: maneuvers, contests, and assessment in the posture-scale movements of interacting zebrafish

Abstract

Two-body fighting behavior occurs throughout the animal kingdom to settle dominance disputes. While some universal features have been identified, important questions such as how the dynamics ultimately lead to a winner and loser remain unresolved. Here we analyze fighting behavior in pairs of adult male zebrafish,Danio rerio. We combine a custom imaging apparatus consisting of multiple cameras, a large volume, and a transparent interior cage to avoid reflection artifacts, with computer vision to track multiple body points across multiple organisms while maintaining individual identity in 3D. In the body point dynamics we find a hierarchy of timescales which we use to construct interpretable joint coordinates consisting of relative orientation and distance. We use the distribution of these coordinates to automatically identify fight epochs and we demonstrate the post-fight emergence of an abrupt asymmetry in relative orientations. To quantify short-time behaviors we cluster transitions between joint configurations, and show that fight epochs are spanned by a small number of dynamical clusters, which we denote as maneuvers. The maneuver clusters include motifs such as “attacks” and “circling” and we quantify longer-time dynamics through maneuver frequencies. We find that the eventual loser attacks more often towards the end of the contest, suggesting a loser assessment component of the dominance decision.