Predators Reduce Prey Population Growth by Inducing Changes in Prey Behavior

The ability of predators to reduce prey populations is generally ascribed to the consumption of prey individuals. However, predators may also induce behavioral changes in prey individuals, which can reduce prey survival and reproduction. Pea aphid populations are impacted by a variety of predators, many of which induce escape responses in individual aphids. We created disturbance-only predators (surgically manipulated predators that were unable to consume prey, but were still able to forage and interact with prey) and measured their ability to suppress aphid population growth over a six-day period. The greatest reduction in aphid population growth was caused by normal predators that were able to both consume and disturb aphids, but aphid population growth was also strongly reduced by nonconsumptive, disturbance-only predators. These field experiments are the first to show that predators reduce prey population growth partly through predator-induced changes in prey behavior, as well as through consumption of prey individuals.