Title of thesis:
Climate change and predator-prey dynamics in alpine ecosystems: A study of ptarmigan and gyrfalcons
Title of trial lecture:
The fast-slow continuum in comparative demography: evolutionary origins and population-level consequences
Evaluation committee:
- First opponent: Professor Jane M. Reid, Department of Biology, Norwegian University of Science and Technology (NTNU), Norway
- Second opponent: Associate Professor Owen R. Jones, Department of Biology, University of Southern Denmark (USD), Denmark
- Internal member: Associate Professor Sam Steyaert, Faculty of Biosciences and Aquaculture (FBA), Nord University, Norway
Supervisory committee:
- Main supervisor: Associate Professor Jan Eivind Østnes, Faculty of Biosciences and Aquaculture (FBA), Nord University, Norway
- Co-supervisor: Professor Erlend Birkeland Nilsen, Faculty of Biosciences and Aquaculture (FBA), Nord University, Norway
- Co-supervisor: Professor Michael A. Patten, Faculty of Biosciences and Aquaculture (FBA), Nord University, Norway
Thesis summary:
Alpine areas are changing rapidly due to a warming climate, which alters seasonality, snow conditions, and phenology. These shifts affect local species communities and their interactions structuring the food web. This thesis studies these changes, with a focus on ptarmigans, key alpine herbivores, and gyrfalcons, one of their main predators. Using long-term monitoring, nest cameras and telemetry data from Norway and other mountain regions, we investigated how weather, snow conditions and interactions with other species shape their dynamics. Gyrfalcons in Norway relied almost entirely on ptarmigan for food and produced more chicks when ptarmigan were abundant. Conversely, when many gyrfalcons decided to breed, ptarmigan survival was lower, suggesting reciprocal predator-prey feedback. However, the impacts of local climate and other species were equally important. Breeding success of both gyrfalcons and ptarmigan varied with spring conditions, and ptarmigan raised more chicks in years with high rodent abundance, likely because predators shifted to rodents. At broader scales, ptarmigan seasonal survival patterns varied with winter intensity and species richness. As warming alters snow regimes, phenology and species distributions, this will have cascading effects on the whole food-web. Overall, this thesis shows that protecting alpine ecosystems requires moving beyond single-species perspectives and recognising the full web of biotic and abiotic factors that shape them.
