Predator-Induced Changes in Prey Behavior Alters the Lipid and Protein Content in Both Prey and Their Resources.

Abstract

AbstractThe general stress paradigm predicts that when prey are exposed to predation risk they will mobilize and divert energy toward risk responses and away from costly somatic growth. However, there is mixed evidence to support this paradigm likely because of the different behavioral strategies prey employ to cope with increased predation risk. Furthermore, this paradigm has rarely been tested in marine systems, where both the prey and their resources can be expected to alter their energetics because of top-down pressure. We performed a laboratory mesocosm experiment using a rocky intertidal system exposing snail prey (Nucella lapillus) to two size classes of two crab predators (Hemigrapsus sanguineus, Carcinus maenas) and recording the number of mussels (Mytilus edulis) eaten. We then measured lipid and protein content of N. lapillus and mussels using proximate composition analysis. We found that, in general, predation risk reduced N. lapillus foraging in all crab treatments but that smaller, more numerous crabs tended to have greater effects than single large ones. We also found that predation risk reduced lipid and protein levels in prey and increased lipid and protein levels within mussels. While crab species or size did not affect prey energetics, we found that smaller crabs had a greater effect than larger ones in driving energy values in mussels-likely due to their greater effects on N. lapillus foraging. Thus, we provide robust evidence in support of the general stress paradigm and add to this framework, showing that predation risk can have cascading effects influencing resource energetics.