Capturing three decades of alpine food-web and climate dynamics with an integrated predator–prey model

Species interactions are fundamental to ecosystem functioning and shape responses to environmental change, yet they are rarely included in climate change predictions. In rapidly warming arctic and alpine regions, low complexity of food webs allows for improved predictions of climate change impacts by integrating species interactions. To test if we can jointly quantify key species interactions in a Norwegian alpine food web, we developed an integrated predator–prey model and fitted it to long-term data on gyrfalcons (specialist predator), ptarmigan (key prey) and rodents (prey for other predators). We estimated prey recruitment and survival, while incorporating feedback loops between prey density, predator breeding probability and prey survival. We also integrated the effects of apparent competition with rodents and climate variability on prey recruitment. Results revealed that gyrfalcon breeding probability increased with ptarmigan density, while ptarmigan survival decreased with gyrfalcon breeding probability. Ptarmigan recruitment was positively related to both rodent density and spring temperature. These findings show that ptarmigan and gyrfalcon dynamics emerge from an integrated system of predator–prey feedback, apparent competition and climate sensitivity. Our approach provides a novel framework to better understand trophic dynamics within simple food webs and emphasises the importance of species interactions for accurate climate change projections.