MSc in Forest and Nature Conservation Stijn Peter Hofhuis at Arctic and Marine Biology (AMB) will Monday 1st of June 2026 hold his trial lecture and defend his thesis for the PhD degree in Natural Science.
Trial lecture on assigned topic will take place at 11.15: “Realized ecological niche shifts in Anthropocene: implications for wildlife conservation and management”
Later, at 13.15 he will defend his thesis entitled: "Space use, population dynamics and management of red foxes in Norwegian tundra ecosystems".
Popular Science Summary
Background: Expanding populations of generalist mesopredators can threaten ecosystem structure and function by outcompeting and predating on native specialist species. In tundra ecosystems, this is exemplified by an increase in red foxes (Vulpes vulpes). Their expansion from the boreal zone has been linked to human impacts that alleviate food-scarcity constraints. Red foxes in Fennoscandian tundra ecosystems threaten endemic populations of arctic foxes (Vulpes lagopus) and ground nesting birds. Here, management includes red fox harvest but its effect on red fox population dynamics is uncertain. This thesis contributes with knowledge on environmental drivers of red fox expansion and provides management recommendations.
Methods: We developed an integrated population modelling workflow that combines multiple data sources to quantify red fox population dynamics on the low Arctic tundra of Varanger Peninsula over a 20-year period of intense and large-scale harvest. We further used GPS telemetry to study space use and habitat selection in relation to environmental variables that likely represent gradients in food resource densities on Varanger Peninsula; distance to the marine coastline, human infrastructure density, and vegetation productivity. Finally, we studied environmental drivers of red fox activity on arctic fox dens across Norway by using proximity to infrastructure, growing degree days, and mean reindeer density or mean calf weight within reindeer herd-ranges (likely related to carrion availability) as predictor variables.
Results: Red fox population size on Varanger Peninsula fluctuated greatly, mainly in response to changes in natural mortality and immigration rate, driven by changes in small rodent (prey) abundance and population density. Harvest appears to limit long-term population growth but is unlikely to evoke population decline due to density-dependent demographic rates. Space use increased during winter and was affected by coastline proximity and infrastructure densities in terms of smaller home range size and habitat selection within home ranges. Red fox activity on arctic fox dens increased with infrastructure proximity, growing degree days, reindeer density, and lower reindeer calf weight.
Conclusions: Intensive and large-scale harvest may limit long-term red fox population growth, but effects are reduced by high mobility and density-dependent demographic rates. Increased but temporary effects of harvest may be achieved during late spring and summer when red foxes are less mobile and vulnerable tundra species are breeding. Reducing the availability of reindeer carrion and human food subsidies associated with infrastructure are viable alternative management solutions that address underlying drivers of red fox expansion.
Evaluation Committee
Supervisors
Streaming
Both the trial lecture and defense and will be streamed and recorded:
Thesis
The thesis is available in Vitenarkivet