An underwater Serengeti: Seagrass-mediated effects on intake and cultivation grazing behavior of a marine megaherbivore

Populations of green turtles (Chelonia mydas), a megaherbivore that consumes seagrasses via cultivation grazing, are recovering worldwide. Information on plant-mediated effects on herbivore foraging behavior is critical to understanding plant-herbivore interactions and sustainability of grazing as ecosystems continue to change. In a Caribbean seagrass ecosystem, we use stationary cameras and benthic surveys to evaluate effects of seagrass morphology and leaf nitrogen content on green turtle grazing behavior. Thalassia testudinum leaf morphology has significant effects on forage intake (mg dry mass [DM] min-1) for green turtles, whereas leaf nitrogen content has no effect. Intake increases in grazed areas with shorter leaves and higher leaf biomass concentration (mg DM cm-3), indicating more efficient foraging under these conditions. Bite rate (bites min-1) increases in grazed areas with short leaves, a result of reduced search time. Bite size (mg DM bite-1) increases in grazed areas wit...