| The study of predator-prey behavior is of primary importance to the field of ecology. However, few studies measure interactions between predators and their most dangerous prey. The objective of this project was to improve understanding of the behavioral and ecological interactions between cursorial predators and dangerous prey in free-living systems. Specifically, I used data from Yellowstone National Park to evaluate 1) the role of cooperative hunting in the ability of predators to hunt dangerous prey, 2) how predator preference for differentially dangerous prey species changes in relation to their relative abundance, 3) the ability of cursorial predators to drive large-scale, landscape level shifts in prey habitat use, and 4) how the kill rate of a top predator was affected by the presence of another. In chapter 2, I found that wolves (Canis lupus) were more cooperative when hunting bison (Bison bison), their most dangerous prey, than when hunting elk (Cervus elaphus). The results from chapter 3 suggest that wolves in northern Yellowstone attacked and killed disproportionately more of the rarer, but safer prey species; wolves maintained a strong preference against bison, even when this species was more than twice as abundant as elk. Analyses of wolf-bison behavioral interactions indicate that wolf preference against bison likely reflected an inability to consistently overcome bison antipredator defenses. Chapter 4 presents several lines of evidence suggesting wolves are a plausible mechanism behind recent decreased bison preference for Yellowstone's high elevation winter range. For example, bison preference for the high elevation Pelican Valley region decreased after wolf reintroduction. This preference was strongly influenced by snow-cover, a proxy for predation risk. In Chapter 5, I collaborated with Scandinavian ecologists to determine how wolf kill rate was affected by a sympatric apex predator, the brown bear (Ursus arctos). My results suggest brown bear presence resulted in wolves killing less frequently in both Scandinavia and Yellowstone. My research contributes to the current body of work addressing the effects of wolf reintroduction in Yellowstone, and sheds light on the behavioral relationships at play in a special type of predator-prey interaction: predators that hunt dangerous prey. |
