Predator-Specific Mortality of Pronghorn on Yellowstone's Northern Range

Abstract

Yellowstone National Park supports a small population (<300) of pronghorn (Antilocapra americana). Some individuals migrate during summer to areas characterized by reduced visibility, mixed habitat types, and a diverse predator community. Across areas selected by migratory and nonmigratory pronghorn, we documented cause-specific mortality of adults and fawns and assessed relative risk of predation by various predators. Coyotes (Canis latrans) accounted for 56% of adult predation and up to 79% of fawn predation. Cougars (Puma concolor) and wolves (Canis lupus) accounted for additional predation of adults, while cougars, black bears (Ursus americanus), and Golden Eagles (Aquila chrysaetos) were documented killing fawns on rare occasions. Our results suggest that even when pronghorn are in the presence of multiple predator species, coyote predation on adults and fawns may predominate for populations inhabiting shrubsteppe habitat. However, the risk of predation by sympatric predators, particularly cougars, may be high for female pronghorn selecting mixed cover types during migration or for birthing purposes. While the direct effect of wolves on overall mortality was low, wolves may indirectly influence survival rates of adult females and fawns by altering the behavior and space use of sympatric predators, particularly coyotes.