Fruit-Catching Fish Tune Their Fast Starts to Compensate for Drift

Abstract

Numerous animal navigators are not simply at the mercy of winds and currents but cope with drift to reach their goals. Here, we report how a fruit-catching Costa Rican fish combines an analysis of aerial motion with a novel way of compensating for drift to optimize its catching success. In the field, schools of this riverine fish never waited until a falling fruit actually landed in the stream. Rather, the fish responded to visual motion and started early to arrive on time at the spot where their food would land. To be successful with their early starts, the fish must cope with the strong relative drift that arises, because the fish, but not their airborne target, experience strong flow on their way toward the fruit's landing point. Surprisingly, the fish solve this problem right at the beginning-by turning rapidly and taking an initial aim that is already optimally adapted to the prevailing drift, so as to lead them straight to their food. Fruit-catching fish thus provide a stunning case of how rapidly animals can generate drift-compensating trajectories in their everyday local lives.