  An effective evasion strategy allows prey to survive encounters with
predators. Prey are generally thought to escape in a direction that is either
random or serves to maximize the minimum distance from the predator. Here we
introduce a comprehensive approach to determine the most likely evasion
strategy among multiple hypotheses and the role of biomechanical constraints on
the escape response of prey fish. Through a consideration of six strategies
with sensorimotor noise and previous kinematic measurements, our analysis shows
that zebrafish larvae generally escape in a direction orthogonal to the
predator's heading. By sensing only the predator's heading, this orthogonal
strategy maximizes the distance from fast-moving predators, and, when operating
within the biomechanical constraints of the escape response, it provides the
best predictions of prey behavior among all alternatives. This work
demonstrates a framework for resolving the strategic basis of evastion in
predator-prey interactions, which could be applied to a broad diversity of
animals.
