The robophysics of fish schooling behavior

Fish schooling behavior is a canonical example of collective animal movement. The most commonly proposed explanation is that moving as a collective saves energy by reducing the cost of transport compared to the cost of moving alone. But direct measurements of energy saving by fish schools have proven difficult to obtain, and understanding how such savings might be achieved involves the analysis of fish body kinematics and hydrodynamics of individuals within a school. We have used a robophysical approach to understand energy saving dynamics of fish schools as groups of fish move over a range of speeds. We directly measured the oxygen consumption of schools and individuals swimming alone to understand how energy use changes with speed and we demonstrate a substantial reduction in the cost of transport by swimming in a group. Fish are constantly rearranging their locations with a school with respect to other individuals. To understand how different fish positions within a school can generate energetic savings, we studied (1) robotic models of fish moving in different relative positions, (2) live individual fish and fish schools interacting with mechanical swimming fish, and (3) conducted computational fluid dynamic simulations of fish groups in different positions.