Dances like wolves? Evaluating ecological replacement of apex predators in eastern North America

Global reductions in large carnivore populations have likely contributed to range expansions by some mesopredators; however, it remains unclear to what extent these smaller carnivores can ecologically replace large carnivores. To test this replacement hypothesis, I used diet studies and cause-specific ungulate mortality studies to compare the dietary ecology of coyotes and wolves in eastern North America, a region which coyotes colonized in the last 120 years in the wake of wolf extirpation. Broadly, I found that coyotes had more diverse diets than wolves, but southeastern coyote diets were more similar to red wolves than northeastern coyote diets were to northeastern wolves. Across both regions, primary producers (i.e., fruit) were much more common in coyote samples (25-33%) compared to wolves (2-3%). In contrast, medium-sized herbivores (i.e., beaver, nutria) were much less common in coyote samples (10-13%), compared to wolves (45%). Coyotes ate smaller mammals than northeastern wolves, likely driven by their inability to kill the largest ungulates. Indeed, coyotes were not documented killing any moose in the mortality studies I reviewed, while wolves were responsible for a significant portion of adult moose and calf mortality. In the northeast, coyotes were responsible for more white-tailed deer fawn mortality (28% vs. 15% for wolves) and a similar percentage of adult mortality (18-22%). In the Southeast, coyotes were responsible for 40% of fawn mortality and 6% of adult deer mortality. These results suggest that coyotes and wolves have different but complementary impacts on white-tailed deer age classes, with predation risk from coyotes more temporally constrained and weaker indirect effects from coyotes related to killing adult large herbivores. Taken together, I show that coyotes likely have broader ecological effects than wolves, but the lack of evidence that they can regularly kill several important mammal species (moose, beaver, nutria) suggests that their capacity to replace wolves is restricted, particularly in the northeast.