Saltatory search in virtual prey does not affect predation risk from fish predators

Abstract

Movement is integral to biological interactions at every scale and, within animal behaviour, links cognition, locomotion and ecological interactions. Saltatory movement is a stop-and-go pattern of motion found across a wide variety of taxa, but little is known about how it affects the vulnerability of moving prey to their predators. Intermittent periods of pause in saltatory movement decrease activity, which has previously been linked to an adaptive reduction in conspicuousness in prey. Accordingly, we predicted that predators would attack constantly moving prey more than prey with saltatory movement. Using a system of three-spined stickleback, Gasterosteus aculeatus, predators attacking simulated virtual prey, we investigated how saltatory movement of prey affects their risk of predation. Computer-generated dots (simulated prey) were programmed to vary in the percentage of time they were stationary (0%, 20%, 40% or 60%). We found no evidence that the fish preferred to attack prey depending on the time the prey spent stationary. Randomization tests revealed that prey speed did not influence the predator's choice of which prey to attack, and that the predator's timing of when to attack was not affected by either the time since the prey's last pause or the duration of that pause. Saltatory search, therefore, appears no more beneficial, or costly, than constant motion in terms of vulnerability to predation. This prompts further questions on the costs and benefits of saltatory motion, how predators perceive intermittent motion, and (more broadly) the relationship between movement and predation risk.