A Ugandan national park is being divided in half to test whether large mammals like antelope and buffalo change their behaviour to avoid human poachers, and whether those choices ripple through the entire food web. Ecologists have long known that predators scare prey into making costly trade-offs—spending less time feeding to avoid being eaten—and that these non-lethal effects can reshape ecosystems. But humans, as the planet’s dominant predator, have been left out of that picture. This project asks two concrete questions: have large animals evolved defences specifically triggered by human hunting, and do those behavioural shifts cascade down to affect plants, smaller animals, and nutrient cycles? Without answers, conservation and land-use planning operate in the dark. If the research succeeds, it will reveal whether human predation—even from subsistence poaching—acts as a hidden steering wheel on savanna ecosystems. That could change how protected areas are designed, where anti-poaching patrols are prioritised, and how wildlife corridors are placed. The work is fundamental ecology, not applied management, but understanding how top predators (including us) shape food webs is the kind of mechanistic insight that eventually informs everything from rewilding projects to crop-raiding mitigation.
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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.
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