Meeting Abstract
Theories of pursuit and evasion suggest that predators can maximize their chances of success by adopting an intermediate speed – one that is fast enough to rapidly gain on prey, but not so fast that they will vastly overshoot their target if it performs a sharp maneuver. Similarly, despite the fact that evasion is a matter of life or death for the prey, moving at maximum velocity may reduce the prey’s ability to maneuver and increase the risk of errors or injuries. Despite some elegant theoretical work on these topics, few studies have directly measured the movement velocities of freely behaving predators and prey. We performed predation trials to quantify the flight speeds and behavioral strategies of wild-caught dragonflies pursuing a variety of prey, including fruit flies, mosquitoes, and house flies. We filmed >150 predation attempts with high-speed cameras, and found that dragonflies typically reach peak accelerations of 15-20 m/s2 within 1-2 wing beats of take-off, and attain maximum velocities shortly before prey capture. Dragonfly velocity was strongly correlated with prey velocity: more than 60% of variability in dragonfly peak velocity during successful captures was explained by prey velocity, following the simple relationship of dragonfly velocity = prey velocity + 1 m/s. Failed pursuits were more often characterized by peak dragonfly velocities that fell below (or occasionally above) this relationship. Prey were more likely to escape if they flew at high speeds while performing erratic, unpredictable turns. Our data thus support the idea that predators and prey adopt movement speeds aimed at rapidly minimizing (or maximizing) the distance between one another, without compromising their ability to perform sudden maneuvers.
