Predator identity and time of day interact to shape the risk–reward trade-off for herbivorous coral reef fishes
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Non-consumptive effects (NCEs) of predators occur as prey alters their habitat use and foraging decisions to avoid predation. Although NCEs are recognized as being important across disparate ecosystems, the factors influencing their strength and importance remain poorly understood. Ecological context, such as time of day, predator identity, and prey condition, may modify how prey species perceive and respond to risk, thereby altering NCEs. To investigate how predator identity affects foraging of herbivorous coral reef fishes, we simulated predation risk using fiberglass models of two predator species (grouper Mycteroperca bonaci and barracuda Sphyraena barracuda) with different hunting modes. We quantified how predation risk alters herbivory rates across space (distance from predator) and time (dawn, mid-day, and dusk) to examine how prey reconciles the conflicting demands of avoiding predation vs. foraging. When we averaged the effect of both predators across space and time, they suppressed herbivory similarly. Yet, they altered feeding differently depending on time of day and distance from the model. Although feeding increased strongly with increasing distance from the predators particularly during dawn, we found that the barracuda model suppressed herbivory more strongly than the grouper model during mid-day. We suggest that prey hunger level and differences in predator hunting modes could influence these patterns. Understanding how context mediates NCEs provides insight into the emergent effects of predator–prey interactions on food webs. These insights have broad implications for understanding how anthropogenic alterations to predator abundances can affect the spatial and temporal dynamics of important ecosystem processes.
KeywordsFlorida Keys coral reefs Landscape of fear Behaviorally mediated indirect interaction Predator–prey interactions Predator hunting mode Predation risk Trophic cascade
Funding for this work was provided by an NOAA Coral Reef Conservation Program grant to D.E.B and B.I. Ruttenberg, an award from Florida International University to K.M.B, a cooperative agreement with NOAA (NA10OAR4320143), and a generous gift from the Medina Family Foundation to the Medina Aquarius Program. This is contribution #20 from the Marine Environment and Research Center in the Institute for Water and Environment at Florida International University. We are indebted to M. Heithaus, J. Fourqurean, A. Shantz, C. Lopez, M. Rojas, R. Malossi, A. Zenone, and C. Catano for their time and advice with this project. We thank the personnel of FIU’s Aquarius Reef Base, Key Largo, FL, USA, for their assistance facilitating this research. This work was conducted with permission from the Florida Keys National Marine Sanctuary under permit no. FKNMS-2013-141.
Author contribution statement
LBC, DEB, KMB, and MBB designed the study; LBC and MBB performed the research; LBC conducted statistical analyses; LBC, DEB, and KMB wrote the manuscript; all authors contributed to editing.
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