Testing the human shield hypothesis: female wild turkeys have greater fitness near human activity

<p>Predator-prey dynamics are driven by trade-offs between resource acquisition and risk avoidance, with prey behavior and fitness shaped by both consumptive and non-consumptive effects. Human activity adds complexity to predator-prey dynamics. Humans can either act as super-predators through direct harvest or create refuge from natural predators. The human shield hypothesis suggests that proximity to human activity benefits prey by reducing predation risk, as predators tend to avoid humans. In hunted landscapes where both predators and prey are harvested, the benefits of the human shield may hinge on individual behaviors. However, the role of consistent among-individual differences in behavior (i.e., behavioral types) in influencing fitness, especially for non-targeted females in male-only harvest systems, remains largely unknown. Using GPS data from <em>n</em> = 200 female wild turkeys, we examined how proximity to human activity (i.e., secondary roads) and predation risk (i.e., shrub landcover) influenced survival and reproduction. Applying a univariate modeling framework, we quantified variation in behavioral types for both risk-taking measures and evaluated fitness outcomes to test whether human activity functioned as a protective shield. We found significant individual variation in both risk-taking measures (distance to secondary roads— r = 0.39, 95% CrI = 0.35, 0.44; distance to shrub landcover— r = 0.35, 95% CrI = 0.30, 0.40). Importantly, we found support for the human shield hypothesis. Females that occurred closer to human activity had greater fitness than females that occurred closer to risky areas associated with predators. Consistent with the human shield hypothesis, female wild turkeys also occurred closer to human activity during critical nesting stages, such as incubation and brooding, which is when predation risk is at its peak. Our findings indicate that human activity can create a protective shield that deters predators and enhances survival and reproduction for prey species of conservation concern. Because habitat work on public lands often occurs in areas accessible to heavy machinery, such as secondary roads, managers can pair habitat manipulations with regular, light human presence in those locations to improve survival and reproduction of subordinate species and deliver strong conservation returns. Our results emphasize the need for further research on the human shield hypothesis that explicitly incorporates among-individual differences in behavior and links them to fitness, to better understand how human recreation affects game populations.</p>