Recolonizing carnivores: Is cougar predation behaviorally mediated by bears?

Kristin N Engebretsen,Jon P Beckmann,Pat Jackson,Alyson Andreasen,Carl W Lackey,Julie K Young,Cody Schroeder

doi:10.1002/ece3.7424

Abstract

Conservation and management efforts have resulted in population increases and range expansions for some apex predators, potentially changing trophic cascades and foraging behavior. Changes in sympatric carnivore and dominant scavenger populations provide opportunities to assess how carnivores affect one another. Cougars (Puma concolor) were the apex predator in the Great Basin of Nevada, USA, for over 80 years. Black bears (Ursus americanus) have recently recolonized the area and are known to heavily scavenge on cougar kills. To evaluate the impacts of sympatric, recolonizing bears on cougar foraging behavior in the Great Basin, we investigated kill sites of 31 cougars between 2009 and 2017 across a range of bear densities. We modeled the variation in feeding bout duration (number of nights spent feeding on a prey item) and the proportion of primary prey, mule deer (Odocoileus hemionus), in cougar diets using mixed‐effects models. We found that feeding bout duration was driven primarily by the size of the prey item being consumed, local bear density, and the presence of dependent kittens. The proportion of mule deer in cougar diet across all study areas declined over time, was lower for male cougars, increased with the presence of dependent kittens, and increased with higher bear densities. In sites with feral horses (Equus ferus), a novel large prey, cougar consumption of feral horses increased over time. Our results suggest that higher bear densities over time may reduce cougar feeding bout durations and influence the prey selection trade‐off for cougars when alternative, but more dangerous, large prey are available. Shifts in foraging behavior in multicarnivore systems can have cascading effects on prey selection. This study highlights the importance of measuring the impacts of sympatric apex predators and dominant scavengers on a shared resource base, providing a foundation for monitoring dynamic multipredator/scavenger systems.

Highlights

Populations of many apex predators have declined globally from causes such as habitat fragmentation, prey loss, overexploitation, and human persecution (Ripple et al, 2014; Younger et al, 2016)
To determine the direction of prey switching when alternative large prey is available, we modeled the proportion of horses in cougar diet for the Great Basin dataset only, since there are no feral horses in the Sierra Nevada
Our analyses show the importance of considering multiple factors that may influence the foraging behavior of a large carnivore when assessing the influence of a recolonizing intraguild competitor

Summary

| INTRODUCTION

Populations of many apex predators have declined globally from causes such as habitat fragmentation, prey loss, overexploitation, and human persecution (Ripple et al, 2014; Younger et al, 2016). Cougars are solitary hunters and habitually cache their large ungulate kills for feeding bouts over several days Across their diverse range, cougars are dominant competitors in their interactions with mesopredators, such as coyotes (Canis latrans) or ocelots (Leopardus pardalis), but they are subordinate competitors when sympatric with large carnivores, such as black bears, wolves, and jaguars (Panthera onca; Elbroch & Kusler, 2018, Elbroch et al, 2015). Cougars are dominant competitors in their interactions with mesopredators, such as coyotes (Canis latrans) or ocelots (Leopardus pardalis), but they are subordinate competitors when sympatric with large carnivores, such as black bears, wolves, and jaguars (Panthera onca; Elbroch & Kusler, 2018, Elbroch et al, 2015) Both cougars and black bears were thought to have been widely distributed in the Great Basin Desert, at low densities (Berger & Wehaussen, 1991; Lackey et al, 2013). The goal of our study was to examine predation and competition in populations of sympatric predators and dominant scavengers where the interspecific competition for prey resources is relatively novel

| MATERIALS AND METHODS

Findings

| DISCUSSION