Predator diversity can impact ecosystems by influencing the strength of a trophic cascade. However, the direction of even the most basic community- and ecosystem-level impacts of predators and predator diversity is highly context dependent and difficult to predict. This ambiguity may arise because predators are complex, often capable of sophisticated behavioral interactions with each other and their prey. Although such non-consumptive interactions are common in marine systems, the community-level behavioral ramifications of multiple predator assemblages are largely unexplored. Here we used a model oyster reef food web to quantify how changes in the behavior of surviving prey influence ecosystem functioning, and how these effects change with varying predator identity and richness. In a two-month field experiment, predators (oyster toadfish, blue and stone crabs) were caged in artificial oyster reefs and either allowed or prevented access to their prey, mud crabs.
Predator identity influenced both total and non-consumptive predator effects on oyster reef functioning. Predator identity influenced prey and resource (oyster spat) survivorship, as well as sediment organic matter and the recruitment of shellfish and other infauna. In non-consumptive treatments, effects on oyster survivorship were found to attenuate with distance from some caged predators, indicating potential predator identity effects on prey distribution and/or foraging behavior. Responses to predator polycultures were similar to that of oyster toadfish alone, highlighting the importance of predator identity for both consumptive and non-consumptive predator effects. Understanding how predators affect adjacent trophic levels, and how changes in the predator community influence these effects, is important for identifying factors maintaining biodiversity and ecosystem functioning.