| Communities consist of prey species that are consumed by a variety of predators under a range of conditions. This high trophic connectivity and variation in environmental context produce many direct and indirect interactions. These interactions can be caused by changes in animal behavior, yet little is known about behavioral indirect effects. I experimentally tested the importance of animal behavior in modifying consumer interactions as a function of hydrodynamic conditions, habitat, and multiple predator effects (MPEs) in the shallow rocky subtidal community, Gulf of Maine, U.S.A. Additionally, I examined the general importance of MPEs, by conducting a quantitative review using meta-analysis.;A combined theoretical and experimental approach showed that chronic, low-level hydrodynamic forces (rather than storm-generated forces) were sufficient to modify the movement behavior of the green urchin, Strongylocentrotus droebachiensis and the seastar, Asterias forbesi. Thus, water flow reduced urchin and seastar abundance and produced a positive indirect effect on their prey (kelp and mussels).;Movement behavior of urchins also changed as a function of habitat. Urchin movement was significantly lower in algal (Codium fragile) dominated habitats than in barren or mussel (Mytilus edulis) habitats. In addition, no urchin crossed into a mussel habitat, whereas the other habitat borders were permeable.;Crab (Cancer borealis) predation on urchins showed strong variation due to habitat. Urchin mortality was significantly greater in Codium and barren habitats than in the mussel habitat. In the barrens, urchin reduction indirectly increased the abundance of the introduced ascidian, Diplosoma sp. Mussels produced a positive indirect effect on urchins by changing the behavior of crabs; crabs feed on mussels instead of urchins (prey switching). Changes in predator behavior also produced significant risk-reductions to urchins in the Codium and barren habitats when the American lobster, Homarus americanus, was introduced.;Meta-analyses revealed that freshwater and marine systems produce significant risk-reductions to prey populations. Multiple predators produce significant risk-reductions when they physically interact and risk-enhancements when predators forage for the same prey, but in different habitats.;These results illustrate the importance of animal behavior in modifying consumer pressure and community structure through direct and indirect pathways in a relatively simple community. |
