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Multiple predator effects in an intertidal food web
Article first published online: 17 OCT 2005
DOI: 10.1111/j.1365-2656.2005.01019.x
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How to Cite
VAN SON, T. C. and THIEL, M. (2006), Multiple predator effects in an intertidal food web. Journal of Animal Ecology, 75: 25–32. doi: 10.1111/j.1365-2656.2005.01019.x
Publication History
- Issue published online: 17 OCT 2005
- Article first published online: 17 OCT 2005
- Received 5 March 2005; revised version accepted 8 July 2005
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Keywords:
- amphipods;
- emergent effects;
- predation;
- predator-specific responses;
- risk enhancement
Summary
- 1We examined the effects of multiple predators from an intertidal boulder food web to test whether and how three different predator species affected the survival of a small amphipod species.
- 2Predators were chosen because they differ in their foraging mode, two feeding at the bottom and in benthic refuges (nemertean and shrimp) and one in the water-column (juveniles of a fish).
- 3Mortality of amphipods was not affected by nemerteans, but was high in the presence of shrimp or fish. Highest mortalities were observed in predator-combinations that contained both shrimp and fish. Amphipods responded to shrimp by escaping into the water column, while they avoided fish by remaining in the refuge. We conclude that predator-specific defence causes conflicts for prey when both shrimp and fish are present.
- 4Comparing observed effects of multiple predators with expected effects revealed risk enhancement for the shrimp + fish combination. A comparison of different predictive models revealed that the multiplicative model was most appropriate, although additive models may work well under certain conditions.
- 5Based on known consumption-ranges of the predators used, we conclude that nemerteans were saturated with prey while fish were far from their saturation point. A predator's functional response curve (prey consumption in relation to prey abundance) determines its impact on prey populations. This knowledge appears essential in order to predict whether prey organisms face risk enhancement, risk reduction or additive effects of multiple predators.