Modelling predation: Theoretical criteria and empirical evaluation of functional form equations for predator-prey systems

Correct modelling of relationships between predators and prey is crucial to ecological and population dynamics models. However, and despite a long-standing competition between ratio and prey-dependent models (and a few alternative intermediate forms) in the literature, most equations currently used to represent such relationships do not meet theoretical criteria for biological consistency. This research proposes a set of universally applicable criteria for all predation equations and shows that the most commonly used predation equations in the literature fail to meet these same criteria. We follow with a proposal for a new predation equation that does meet these criteria, which combines both prey and ratio-dependent concepts while giving reasonable predictions in the cases of both high predator or high prey densities. We show its empirical performance by applying the new equation, along with existing alternatives, to various experimental predation datasets from the literature. Results show that the new equation is not only more mathematically consistent than existing equations, but also performs more consistently empirically across different datasets from various ecological situations. This research is the first to propose a systematic set of criteria to evaluate predation equations and then to offer an equation that meets these criteria and also performs well both theoretically and empirically across datasets from a wide range of predation systems.