Scientists discovered that common methods used to study how multiple predators affect prey survival are systematically biased, leading to overestimation of predator interactions in ecological studies. The bias occurs because current methods assume predators maintain constant feeding rates, but in reality feeding rates change as prey become depleted during experiments. The researchers used mathematical modeling to simulate predation experiments, comparing results from the standard 'Multiplicative Risk Model' used by ecologists with more realistic models that account for prey depletion and nonlinear predator feeding responses over time. The standard Multiplicative Risk Model used in predator studies is biased because it assumes constant feeding rates, but real predators have nonlinear responses that change as prey are depleted. Studies using additive experimental designs were more likely to incorrectly conclude 'risk enhancement' (predators working together kill more prey than expected). Studies using substitutive designs usually incorrectly concluded 'risk reduction' (predators working together kill fewer prey than expected). On average, prey were depleted by 70% over the course of experiments in 100 multiple predator studies they examined. The research suggests that decades of ecological studies may have overestimated how often predators interact in meaningful ways, potentially leading to incorrect conclusions about food web dynamics and ecosystem management strategies. The findings affect how we understand predator-prey relationships that form the foundation of marine and terrestrial food webs.
Citation
McCoy, Michael W.; Stier, Adrian C.; Osenberg, Craig W. (2012). Emergent effects of multiple predators on prey survival: the importance of depletion and the functional response. Ecology Letters.
Cite this article
McCoy et al. (2012). Model Structure Can Bias Estimates in Predator Studies. Ocean Recoveries Lab. https://doi.org/10.1111/ele.12005
