Predicting how the inducible defences of large mammals to human predation shape spatial food web dynamics

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Exploring the mechanisms that structure food webs has been a cornerstone of ecological inquiry for over a century. The importance of predator-prey interactions, particularly among large animals near the apex positions of trophic systems, has been highlighted. Predators exert consumptive, also known as lethal, effects (CEs), and nonconsumptive effects (NCEs), represented by the fitness-compromising tradeoff decisions that prey make to avoid predation (i.e., NCEs). The nature and strength of these CEs and NCEs can cascade down trophic systems and drive the evolution of defences in prey induced by predation. Much has been learned from this research effort and yet, two vital knowledge gaps persist, both relating to human predation at the top of food chains. First, it is not known whether large animals have evolved defences that are induced by human predation. This is unclear because the costs of large animal decisions in response to human predation have not yet been properly quantified. Second, the impact of human-induced NCEs on food web dynamics has not been measured. Consequently, it is not known whether human predation exerts effects that can cascade down trophic systems. I will fill these major voids in ecological understanding via experimental study of a Ugandan large mammal system experiencing human predation from subsistence poaching. Dividing my 880 km2 study area into equal-sized treatment (where subsistence poaching is common) and control (where subsistence poaching is naturally rare because of distance from human community) portions, I will quantify the costs of large mammal decisions and fit habitat domain models to elucidate how human predation shapes food web dynamics. While it is widely known that humans have top-down and bottom-up impacts on trophic systems, my project will articulate the ways in which cascading mechanisms can flow from human predation with important implications in the Anthropocene for every other trophic system on earth.