Predator avoidance behavior in the pea aphid: costs, frequency, and population consequences.

Induced prey defenses can be costly. These costs have the potential to reduce prey survival or reproduction and, therefore, prey population growth. I estimated the potential for predators to suppress populations of pea aphids (Acyrthosiphon pisum) in alfalfa fields through the induction of pea aphid predator avoidance behavior. I quantified (1) the period of non-feeding activity that follows a disturbance event, (2) the effect of frequent disturbance on aphid reproduction, and (3) the frequency at which aphids are disturbed by predators. In combination, these three values predict that the disturbances induced by predators can substantially reduce aphid population growth. This result stems from the high frequency of predator-induced disturbance, and the observation that even brief disturbances reduce aphid reproduction. The potential for predators to suppress prey populations through induction of prey defenses may be strongest in systems where (1) predators frequently induce prey defensive responses, and (2) prey defenses incur acute survival or reproductive costs.