Top-down effects exhibited by apex predators are modulated by human impacts on community composition and species abundances. For these reasons, research supporting strong top-down effects of apex predators occurs almost entirely within protected areas rather than the much more common multi-use landscapes dominating modern ecosystems. Based on 16 years of monitoring, we developed an integrated population model to disentangle the concurrent contributions of a reintroduced apex predator, the gray wolf, human hunting, and prey abundances on vital rates and abundance of a subordinate apex predator, the puma. Increasing wolf numbers had strong negative effects on puma fecundity, and subadult and adult survival. Puma survival was also influenced by density-dependence. Overall, our results showed that puma dynamics in our multi-use landscape were more strongly influenced by top-down forces exhibited by a reintroduced apex predator, than by human hunting or bottom-up forces (prey abundance) subsidized by human activities. Quantitatively, the average annual impact of human hunting on equilibrium puma abundance was approximately equivalent to the effects of 20 wolves. Based on these results, wolves may have limited pumas across North America historically, and dictated puma scarcity in systems lacking sufficient refugia to mitigate the effects of competition.
Monitoring data for individual pumas marked with VHF and GPS collars, delineated in 3-month time steps. Mortality codes, age at capture, and notes included as well. F=female, and M=male. UC=unknown
Code used in analyses are provided in a Word document