Ungulate Responses to Predators in Complex Landscapes of Northern Washington

Abstract

In 2008, after nearly 80 years of absence, gray wolves began to recolonize northern regions of Washington State. Wild ungulates comprise the majority of wolf diets, but the impact of recolonizing wolves on deer and elk in Washington is unknown. Cougars, bobcats, black bears, and coyotes compete with wolves for ungulate prey, while domestic dogs, vehicle collisions, human harvest, disease, and malnutrition also cause ungulate mortality. In my dissertation, I sought to determine how mule deer, white-tailed deer, and elk responded to predators through direct and indirect mechanisms within complex landscapes of wildfire, timber harvest, and human activity in northern Washington. Chapter 2 lays the methodological foundation in which I investigated how DNA evidence can improve the identification of predators at ungulate kill sites. I identified common errors in field-based mortality investigations and the factors contributing to these errors, informing when to prioritize genetic sampling. I also described key differences in predator signs associated with small prey (deer fawns and elk calves) versus adult deer kills. I applied these tools in subsequent chapters when identifying ungulate causes of mortality. In chapter 3, I examined how historic wildfires in north-central Washington shaped habitat structure and forage availability for mule deer, showing that mule deer use of burns depended on the season, wolf and cougar activity, and the characteristics of the fire that had burned there. In chapter 4, I modeled the demographic sensitivity of white-tailed deer to wolves, cougars, coyotes, bobcats, and human land management practices associated with forage availability. The population was co-limited by cougars, wolves, and forage, whereas bobcats and coyotes had less influence on population dynamics. Finally, I examined how elk navigated risk from cougars, wolves, and humans in Chapter 5, showing that elk altered habitat selection between day and night and depending on habitat structure to manage predation risk. Elk strongly avoided humans and predators rather than using areas of human activity as a refuge from predation risk. These findings illustrate how landscape context, particularly disturbance regimes and human presence, influence carnivore-ungulate interactions with important implications for wildlife management and conservation in anthropogenic landscapes.