title: Interactive effects of predation risk and conspecific density on the nutrient stoichiometry of prey.
abstract: The mere presence of predators (i.e., predation risk) can alter consumer physiology by restricting food intake and inducing stress, which can ultimately affect prey-mediated ecosystem processes such as nutrient cycling. However, many environmental factors, including conspecific density, can mediate the perception of risk by prey. Prey conspecific density has been defined as a fundamental feature that modulates perceived risk. In this study, we tested the effects of predation risk on prey nutrient stoichiometry (body and excretion). Using a constant predation risk, we also tested the effects of varying conspecific densities on prey responses to predation risk. To answer these questions, we conducted a mesocosm experiment using caged predators (Belostoma sp.), and small bullfrog tadpoles (Lithobates catesbeianus) as prey. We found that L. catesbeianus tadpoles adjust their body nutrient stoichiometry in response to predation risk, which is affected by conspecific density. We also found that the prey exhibited strong morphological responses to predation risk (i.e., an increase in tail muscle mass), which were positively correlated to body nitrogen content. Thus, we pose the notion that in risky situations, adaptive phenotypic responses rather than behavioral ones might partially explain why prey might have a higher nitrogen content under predation risk. In addition, the interactive roles of conspecific density and predation risk, which might result in reduced perceived risk and physiological restrictions in prey, also affected how prey stoichiometry responded to the fear of predation.
authors.affiliation: Ecology Laboratory CCBS Universidade Federal do Mato Grosso do Sul Campo Grande MS Brazil.
authors.forename: Rafael D
authors.initials: RD
authors.lastname: Guariento
authors.affiliation: Department of Ecology Universidade Federal do Rio Grande do Norte CEP 59072-970 Natal RN Brazil.
authors.forename: Luciana S
authors.initials: LS
authors.lastname: Carneiro
authors.affiliation: Department of Botany and Zoology Universidade Federal do Rio Grande do Norte CEP 59072-970 Natal RN Brazil.
authors.forename: Jaqueiuto S
authors.initials: JS
authors.lastname: Jorge
authors.affiliation: Department of Botany and Zoology Universidade Federal do Rio Grande do Norte CEP 59072-970 Natal RN Brazil.
authors.forename: Angélica N
authors.initials: AN
authors.lastname: Borges
authors.affiliation: Department of Ecology Universidade Federal do Rio de Janeiro Rio de Janeiro RJ Brazil.
authors.forename: Francisco A
authors.initials: FA
authors.lastname: Esteves
authors.affiliation: Department of Ecology Universidade Federal do Rio Grande do Norte CEP 59072-970 Natal RN Brazil.
authors.forename: Adriano
authors.initials: A
authors.lastname: Caliman
keywords: Ecology of stress; non‐lethal effects; nutrient balance; predation risk; stress physiology