Fear effects and group size interact to shape herbivory on coral reefs

Fear of predators (‘fear effects’) is an important determinant foraging decisions by consumers across a range ecosystems. Group size one the main behavioural mechanisms for mitigating fear effects while also providing benefits to group members. Within coral reef ecosystems, have been shown influence feeding rates herbivorous fishes, key functional that prevents macroalgal overgrowth. Yet, how and interact shape removal on reefs remains unclear. Here, we conducted field-based experiments using models common piscivorous fish, leopard grouper Plectropomus leopardus series Sargassum ilicifolium assays positioned at increasing distances from (1, 2, 3 4 m) two in Singapore investigate acute intensity herbivory, whether these were influenced variation fishes assays. We found strongly behaviour over small spatial scales. Rates biomass removal, total number individual events all lower near predator model. These dissipated rapidly with distance model undetectable m. generally larger sizes further model, presumably reflecting decreased risk. Furthermore, bites/event increased significantly browsing Siganus virgatus javus. Our findings highlight distribution herbivory interacted herbivore resulting changes bite collectively realized ecosystem function reefs. context-dependent factor should be considered when examining A free Plain Language Summary can within Supporting Information this article.