Evasion strategies of zebrafish larvae

Evasion maneuvers are primal behavioral responses that rely on fundamental neuro-sensory circuits. In fish, the sensory cues needed for prey to detect predators and initiate their escape are largely unclear, as are the details of the evasion response. Recent experiments on larval zebrafish indicate that evasion maneuvers vary between deterministically optimal and protean (random) strategies, depending on the predator location as perceived by the prey. Here, we propose several models of evasion and compare them to the empirical data. We find that the model derived from the classical notion that prey tend to maximize their distance of closest approach to the predator is not supported by experimental observations. Rather, the behavior is well-explained by parsimonious models requiring far less sensory effort than the classically optimal strategies. These results shed light on the neuro-sensory mechanisms underlying prey evasion, and, in particular, lay the groundwork for a further series of experiments uncovering the source of variation in larval zebrafish escape response.