Effects of human-induced prey depletion on large carnivores in protected areas: Lessons from modeling tiger populations in stylized spatial scenarios.

Neil H Carter,Simon A Levin,Volker Grimm

doi:10.1002/ece3.5632

Abstract

Prey depletion is a major threat to the conservation of large carnivore species globally. However, at the policy‐relevant scale of protected areas, we know little about how the spatial distribution of prey depletion affects carnivore space use and population persistence. We developed a spatially explicit, agent‐based model to investigate the effects of different human‐induced prey depletion experiments on the globally endangered tiger (Panthera tigris) in isolated protected areas—a situation that prevails throughout the tiger's range. Specifically, we generated 120 experiments that varied the spatial extent and intensity of prey depletion across a stylized (circle) landscape (1,000 km2) and Nepal's Chitwan National Park (~1,239 km2). Experiments that created more spatially homogenous prey distributions (i.e., less prey removed per cell but over larger areas) resulted in larger tiger territories and smaller population sizes over time. Counterintuitively, we found that depleting prey along the edge of Chitwan National Park, while decreasing tiger numbers overall, also decreased female competition for those areas, leading to lower rates of female starvation. Overall our results suggest that subtle differences in the spatial distributions of prey densities created by various human activities, such as natural resource‐use patterns, urban growth and infrastructure development, or conservation spatial zoning might have unintended, detrimental effects on carnivore populations. Our model is a useful planning tool as it incorporates information on animal behavioral ecology, resource spatial distribution, and the drivers of change to those resources, such as human activities.

Highlights

Prey depletion is a major threat to carnivore populations around the world, very few studies examine how different spatial configurations of human‐induced prey depletion affect carnivore population dynamics
We found that the spatial patchiness of prey resources influences female tiger territory sizes, which in turn alters the carrying capacity of the landscape for tigers
We found that density‐dependent, fe‐ male mortality due to resource deprivation medi‐ ates the effects of spatially heterogeneous prey depletion on tiger populations

Summary

| INTRODUCTION

Prey depletion is a major threat to the conservation of large carni‐ vore species globally. Previous studies have used indi‐ vidual‐based approaches (Chapron et al, 2016; Imron, Herzog, & Berger, 2011; Watkins, Noble, Foster, Harmsen, & Doncaster, 2015) and perturbation analyses (Gosselin, Zedrosser, Swenson, & Pelletier, 2014; Lewis, Breck, Wilson, & Webb, 2014) to examine the effects of anthropogenic and natural factors on carnivore population dynam‐ ics These studies have made important contributions, they did not explicitly evaluate the effects of spatially varying prey de‐ pletion. Our results will provide insights for understanding and mitigating the effects of spatially varying prey depletion on the population dynamics of carnivores, like tigers In addition to these stylized spatial scenarios, we demonstrate the use of our model for real landscapes, by using the Chitwan National Park, Nepal, as an example

| MATERIALS AND METHODS

| Experiments

| DISCUSSION

Findings

CONFLICT OF INTEREST