Between a Risk and a Hard Place: Scavenging Patterns and Habitat Selection of Carnivores in the Subarctic Kaija Klauder A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science University of Washington 2018 Committee: Laura Prugh Bridget Borg John Marzluff Program Authorized to Offer Degree: School of Environmental and Forest Sciences ÓCopyright 2018 Kaija Klauder University of Washington Abstract Between a Risk and a Hard Place: Scavenging Patterns and Habitat Selection of Carnivores in the Subarctic Kaija Klauder Chair of the Supervisory Committee: Laura Prugh School of Environmental and Forest Sciences Animals must balance the need to acquire sufficient resources against the risk of being consumed by a predator. This challenge is faced by many species which, though predatory, are also subject to predation. The ecological relationship between top predators and these smaller "preydators" is a complex mix of competition, facilitation, and predation. Two arenas in which smaller predators must balance fitness needs with predation risk are at carcass sites, which represent a valuable but risky food source, and when making habitat use decisions in a landscape populated with top predators. In this thesis, I use photo data from carcass sites and location and survival data from sympatrically collared wolves (Canis lupus) and coyotes (Canis latrans) to examine the behavior and risk-mediation strategies of carnivores in an understudied environment: the subarctic. I found that carrion use was dominated by wolves and wolverines (Gulo gulo), with limited use by coyotes (Canis latrans) and red foxes (Vulpes vulpes). Risk-mediation while scavenging occurred primarily through alterations in use intensity rather than behavior. I show that coyotes do not universally avoid wolves, but instead demonstrate season-- iii specific responses to wolf risk. Specifically, although coyotes avoided wolf proximity under all circumstances, they switched from avoiding areas of long term wolf use in the summer to favoring them in the winter. These findings suggest that although inter-guild competition for carrion and space has strong effects, mesocarnivores use context-specific behavioral strategies to mediate the risk of apex carnivores. Future studies of carnivore population dynamics should account for these species-specific and context-dependent behaviors. iv Table of Contents Table of Contents ..................................................................................................................................... v List of Figures ........................................................................................................................................ vii List of Tables .......................................................................................................................................... ix Acknowledgements ................................................................................................................................ xi Chapter One: General Introduction ...................................................................................................... 1 Works Cited ........................................................................................................................................................ 6 Chapter Two: ........................................................................................................................................... 1 Abstract ............................................................................................................................................................. 10 Introduction ...................................................................................................................................................... 10 Methods ............................................................................................................................................................. 14 Study area ....................................................................................................................................................... 14 Fieldwork ....................................................................................................................................................... 15 Photo coding ................................................................................................................................................... 17 Analyses ......................................................................................................................................................... 18 Results ................................................................................................................................................................ 23 Utilization of Carcass Sites Across Species ................................................................................................... 23 Effect of Site Characteristics on Use and Vigilance ...................................................................................... 25 Temporal Risk Mediation .............................................................................................................................. 29 Return Interval ............................................................................................................................................... 32 Discussion .......................................................................................................................................................... 33 Conclusion ......................................................................................................................................................... 40 Works Cited ...................................................................................................................................................... 41 Supplementary Material .................................................................................................................................. 49 Body Mass ...................................................................................................................................................... 49 Carcass Site Information ................................................................................................................................ 49 Model Results ................................................................................................................................................. 50 Chapter Three: ....................................................................................................................................... 10 Abstract ............................................................................................................................................................. 63 Introduction ...................................................................................................................................................... 63 Methods ............................................................................................................................................................. 67 Study area ....................................................................................................................................................... 67 Fieldwork ....................................................................................................................................................... 69 Coyote home range and survival .................................................................................................................... 69 Habitat variables ............................................................................................................................................. 70 Wolf Risk Variables ....................................................................................................................................... 71 Available locations ......................................................................................................................................... 73 Resource Selection Modeling ........................................................................................................................ 74 Results ................................................................................................................................................................ 75 Coyote Space Use and Survival ..................................................................................................................... 75 Model Selection and Validation ..................................................................................................................... 80 Effects of topography, habitat, and wolf activity ........................................................................................... 80 Discussion .......................................................................................................................................................... 83 Conclusion ......................................................................................................................................................... 89 Works Cited ...................................................................................................................................................... 90 Supplementary Materials .............................................................................................................................