The effects of foraging behaviour on food-web structure and dynamics

Abstract

A food web summarises the foraging relationships among creatures within a community. Therefore, to understand how food-web structural and dynamical properties emerge, it is essential to clarify how foraging behaviour (as the underpinning driver) shapes the properties at the level of the whole food web. In this thesis, we examine the influence of several behavioural aspects of foraging on food webs, as well as the mechanisms that cause these influences. In Chapter 2, by conducting food-web dynamical modelling that is constrained by species’ metabolism (following Metabolic Theory of Ecology, MTE), we bring to light how the foraging strategy and dimensionality interact with food-web structures to determine species coexistence in food webs. In Chapter 3, by further introducing Optimal Foraging Theory (OFT) as a diet choice mechanism, we explore the food-web structural and dynamical consequences when species are able to adjust their diet depending on resource abundances. We show that incorporating OFT indeed significantly affect both the structure and the dynamics of food webs, while the impacts can be varied and dependent on parameters that control the properties of both the community and its species’ behaviour. We then proceed in Chapter 4, by modelling using the same MTEOFT framework, to investigate the emergent food-web structure under conditions where species cannot fully comply with OFT but rather are constrained by the predation risk they undertake. We develop a new model that describes consumers’ diet choice under this predation-risk effect, and find that we can capture better the empirical food-web structure than can the classical OFT model without predation-risk considerations. By showing how foraging strategy and dimensionality, adaptive diet choice, and predation risk-driven response scale up their effect to determine food-web properties, overall, the findings of this thesis shed light on how food-web properties emerge from organismal foraging behaviour. Also, the present thesis lays a firm quantitative foundation for future work in food-web ecology.