A detailed quantification of larval zebrafish behavioral repertoire uncovers principles of hunting behavior.

During goal-directed behavior, animals select actions from a diverse repertoire of movements. Accurately quantifying this complex and high-dimensional repertoire is essential to uncovering the underlying rules that guide the behavior. Here, we developed a low-dimensional mathematical model that accurately reproduces the complete and continuous repertoire of hunting larval zebrafish. We show that fish position and change in heading angle following a movement are coupled, such that the choice of one of them limits the other. This repertoire structure uncovered fundamental principles of movements, showing that fish rotate around an identified rotation point and then move forward or backward. Moreover, it identified a new guiding rule of the hunt: fish turn to face the prey in each movement and then move forward or backward. These results present the first low-dimensional and continuous description of movements repertoire, uncover guiding behavioral rules, and offer insights into the underlying motor control.