Habitat complexity mitigates trophic transfer on oyster reefs

Structured habitats within several aquatic systems have been characterized as having higher abundances of both predators and their prey. Understanding this somewhat paradoxical phenomenon requires teasing apart how habitat complexity influences predator-prey dynamics. To determine whether habitat complexity influences predator foraging efficiency, we measured predator foraging rates within structurally simple and complex habitats. We selected as our test system mud crabs feeding on juvenile hard clams within biogenic reefs formed by the eastern oyster. At low and intermediate crab densities, foraging rates of mud crabs were similar between simple and complex habitats. However, at high crab densities foraging rates were higher for crabs in the complex reefs than in the simple reefs. In addition to providing refuge to both intermediate predators and their prey, habitat complexity appears to enhance predator foraging efficiency by reducing interference competition among predators. In systems where interference competition among densely populated predators may be intense, complex habitats may not provide survival benefits to all trophic levels.