The ecology of fear in estuarine communities: cascading effects of multiple predators

The role of predation has long influenced our understanding of ecological processes from the individual to the landscape level. Recent interest in the role of nonconsumptive effects of predators, or the consequences of prey defensive behaviors in response to predation risk, has revolutionized how ecologists perceive the role of predators in ecological communities. From focusing on how individual predators affect prey risk taking behaviors and foraging tactics, to the consequences of these behavioral shifts for ecosystem functions and services including primary production, nutrient cycling and energy transfer, we now know that the mere presence of predators can sometimes be more important than their lethal effects on prey density. However, predicting the cascading effects of multiple predator assemblages is often challenging and counterintuitive due to the consequences of behavioral interactions among predators and their prey. I tested the effects of predator presence, identity and richness on prey and basal resources in field and mesocosm experiments based on estuarine communities. By allowing predators to scare but not consume their prey, I examined the generality of nonconsumptive predator effects in these systems across multiple predator species. Predators had varying effects on prey density and the strength of a given prey antipredator behavior, with cascading effects on prey populations and resource dynamics over time. The presence of multiple predators heightened prey antipredator behavior, including reductions in foraging rates, and promoted basal resources despite changes in predation risk. Changes in predator diversity may have profound consequences for marine communities by altering the strength of both consumptive and nonconsumptive predator-prey interactions, with consequences for the strength of a trophic cascade. Complex food web models incorporating both consumptive and nonconsumptive pathways are necessary to understand and predict the effects of ongoing declines in predator abundance and diversity