Unveiling the Hidden Feast: from molecular detection to predation rate – An example on biological control by generalist predators

Abstract

Very few processes are as decisive as predation in shaping the structure and dynamics of ecological communities. For most predator species, the number of prey items killed by a predator in a day (predation rate) remains impossible to assess because direct observations are scarce or impossible to acquire. To fill this gap, we propose here a Hierarchical Bayesian Model that integrates data on the molecular detection of prey in predators (e.g. PCR results), on individuals captured in the field on the one hand, and on individuals fed in the laboratory, on the other, in a novel mechanistic framework. By explicitly combining the processes of predation and digestion, model fit provides an estimate of the slope and intercept of the digestion curve, and an estimate of the number of prey consumed by a predator in a day. In a case study targeting 25 carabid beetle species and 5 types of prey in agricultural fields (winter wheat), we use our model to estimate predation rates at species and community scales and demonstrate its advantages for studies on biocontrol and beyond.