Direct and Indirect Cues of Predation Risk Influence Behavior and Reproduction of Prey: a Case for Acarine Interactions

Little is known about the flow of chemical information from higher to lower levels within the animal food chain. However, this information may determine the behavior and distribution of many animals (e.g., that of potential prey) when exposed to direct and indirect cues of predation risk. We used herbivorous spider mites, Tetranychus urticae Koch (Tetranychidae) as a model to examine the foraging and oviposition decisions that prey make when exposed to these cues. We conducted laboratory tests to determine if the previous presence of predators (direct cues) on leaf discs or the presence of injured conspecifics (indirect cues) alters the distribution of adults and eggs of T. urticae. When given a choice, after 24 h, fewer adults and eggs were found on leaf discs that had previously contained specialist spider mite predators, Phytoseiulus persimilis Athias-Henriot (Phytoseiidae), than on discs unexposed to predators. Also, more T. urticae emigrated from predator-exposed discs than from unexposed discs or from those that had previously contained nonpredatory mites (Tyrophagus putrescentiae, Acaridae). Finally, fewer T. urticae foraged and laid eggs on predator-exposed discs or on those with artificially damaged conspecifics (eggs or dead adults) than on discs with intact conspecifics. Tetranychus urticaeprobably recognizes infochemicals (kairomones) from its predators or cues from injured spider mites and consequently avoids feeding or ovipositing in areas exposed to these cues. Recognition and avoidance of kairomones from specialist predators by this prey are likely to be hereditary, but avoidance of injured conspecifics may be an adaptation to avoid predators that are not inherently recognized. We discuss the behavioral and ecological implications of our findings