Data from: Fish prey change strategy with the direction of a threat

Predation is a fundamental interaction between species, yet it is unclear
what escape strategies are effective for prey survival. Classical theory
proposes that prey should either escape in a direction that conforms to a
performance optimum or that is random and therefore unpredictable. Here,
we show that larval zebrafish (Danio rerio) instead use a mixed strategy
that may be either random or directed. This was determined by testing
classic theory with measurements of the escape direction in response to a
predator robot. We found that prey consistently escaped in a direction
contralateral to the robot when approached from the side of the
prey's body. At such an orientation, the predator appeared in the
prey's central visual field and the contralateral response was
consistent with a model of strategy that maximizes the distance from the
predator. By contrast, when the robot approached the rostral or caudal
ends of the body, and appeared in the prey's peripheral vision, the
escape showed an equal probability of a contralateral or ipsilateral
direction. At this orientation, a contralateral response offered little
strategic advantage. Therefore, zebrafish larvae adopt an escape strategy
that maximizes distance from the threat when strategically beneficial and
that is otherwise random. This sensory-mediated mixed strategy may be
employed by a diversity of animals and offers a new paradigm for
understanding the factors that govern prey survival.