DOI: 10.5061/dryad.x3ffbg80z
title: Testing the human shield hypothesis: female wild turkeys have greater fitness near human activity

description: 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 n = 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.
description: # Testing the human shield hypothesis: female wild turkeys have greater
 fitness near human activity Dataset DOI:
 [10.5061/dryad.x3ffbg80z](https://doi.org/10.5061/dryad.x3ffbg80z) ##
 Description of the data and file structure ├── Data │ ├──
 daily_DistanceTO_female_GA_2017_2023.csv              &lt;- Behavioral
 data used in the main analysis     └── Female_Survival_GA_17_23.csv       
                               &lt;- Fitness data used in nest
 fate/survival models ### Files and variables #### File:
 daily_DistanceTO_female_GA_2017_2023.csv **Description:** GPS movement
 metrics used in the main analysis ##### Variables * lineID: line number *
 ID: Transmitter ID for individual wild turkeys * LMT_Date: Date column *
 Phase: phenological phase * SecondRdRast: Distance to secondary road
 (meters) * Shrub: Distance to shrub landcover (meters) * Year: Year data
 was collected * Age: Age of wild turkeys (A = adult; J = Juvenile) *
 Attempt: Nesting attempt #### File: Female_Survival_GA_17_23.csv
 **Description:** Fitness data frame ##### Variables * lineID: line number
 * Site: Study site * Year: Year data was collected  * ID2: Transmitter ID
 for individual wild turkeys * ID: Transmitter ID for individual wild
 turkeys * Age: Age of wild turkeys (A = adult; J = Juvenile) *
 Nest_Fate: Binary nest fate outcome (1= hatched, 0 = failed) *
 Yearly_Survival: Binary survival outcome (1= survived, 0 = dead) ##
 Code/software We used R version 4.3.1 for all statistical analyses.