Multiple predator species alter prey behavior, population growth, and a trophic cascade in a model estuarine food web

Predators can influence prey population dynamics by affecting prey behaviors with strong fitness consequences, with cascading effects on lower trophic levels. Here, we demonstrate that multiple predator species can nonconsumptively influence prey population growth and the strength of a trophic cascade in a model marine community. We exposed the herbivorous amphipod Ampithoe longimana to olfactory and visual cues from three common predators (pinfish, mud crabs, brown shrimp) singly and together in a multiple-predator assemblage to quantify the nonconsumptive effects (NCEs) of predator identity and the presence of multiple predators on prey population and community-level metrics. The presence of predator cues, particularly those of the pinfish and the multiple-predator treatments, decreased prey population growth and influenced primary and secondary production. To explore mechanisms underlying the observed NCEs in the experimental communities and their potential influence in the field, we quantified individual prey behavioral responses (changes in grazing rate, diet preference, dispersal, colonization) in the presence of predator cues. Predator cues decreased prey grazing, dispersal, and colonization but did not affect prey diet preference. Given the persistence of NCEs over time and the fact that trophic cascades are common features of marine systems, changes in marine predator communities may have widespread effects on predator–prey behavioral interactions with consequences for ecosystem function even in areas of weak predation pressure.