| CONTEXT DEPENDENCE OF NONLETHAL EFFECTS OF A PREDATOR ON PREY GROWTH |
SCOTT D. PEACOR A1 and EARL E. WERNER A2
A1 Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824, USA and NOAA Great Lakes Environmental Research Laboratory, 2205 Commonwealth Boulevard, Ann Arbor, Michigan 48105, USA
A2 Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
Predators can have a large influence on their prey through induced changes in prey phenotype. Such "nonlethal" predator effects have been abundantly demonstrated empirically in both terrestrial and aquatic systems. But the extent to which changes in species traits alter short-term responses such as growth rate or probability of survival is not clear. Here we develop models to examine the nonlethal effects of predators on prey growth. Our analyses illustrate how the nonlethal effects of predators on individual prey growth depend on environmental context; e.g., factors such as focal species density, competitor density, resource dynamics, and the timescale over which the interactions occur. This context dependence arises because of complex interactions of three mechanisms; (1) the direct negative effect of induced reduction in foraging rates, which is opposed by (2) the potential positive effects of reductions in intra- and interspecific competition, and (3) resource responses to reduced foraging. We present new empirical work, and review previous work, on larval-anuran growth that is in general support of model predictions. The framework presented here can serve to facilitate the design and interpretation of experimental results and predict how the nonlethal predator effect on prey growth in natural systems will vary over time and space.
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