Effects of predator-rey-body-mass ratios and habitat structure on functional responses

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Functional responses describe the per capita consumption rates of predators in dependence on prey abundance (prey-dependent functional responses), or predator and prey abundances (predator dependent functional responses). The various parameters of these models vary with habitat structure. Different functional response models predict very different consumption rates, and analyses of energy fluxes between predator and prey populations in natural food webs require descriptions of the functional response of each interaction. The high number of predator-prey interactions in natural food webs makes this task intractable thus seriously limiting our understanding of energy fluxes in complex food webs (“quantitative food webs”). In this application, we present an approach to estimating the parameters of prey- and predator-dependent functional responses based on predator-prey body-mass ratios and habitat structure. Laboratory experiments with ground-dwelling spiders and beetles as predators and collembolans, flies and beetle larvae as prey will be carried out to ensure a broad generality of our results across different combinations of predator and prey types under varying habitat structure. Identifying generalities in body-mass ratio effects on functional response will be an important step towards a general model of quantitative energy fluxes in complex food webs.