Spatial and temporal variation in the distribution and abundance of red foxes in the tundra and taiga of northern Sweden

Variation in the distribution and abundance of animals in space and time are key concepts of population ecology. We studied these variations in a population of red foxes (Vulpes vulpes) in the tundra and taiga of northern Sweden. We analysed 12 years (1974-1985) of snow tracking data from a large area of 65,375 km(2). Specifically, we evaluated to what extent the distribution of red foxes was explained by the presence of prey and how this interacted with snow depth and altitude. We also tested for temporal linear trends in the distribution and abundance of red foxes during the study period. The distribution of red foxes was explained by the presence of rodents, hares, tetraonid species, and ungulates (i.e. carcasses). Snow depth had a negative effect on the impact of small prey on the distribution of the red foxes, whereas it had a positive effect on the impact of ungulates. The influence of hares increased with altitude. Neither distribution nor abundance of red foxes showed a positive or negative linear trend, suggesting a stable population in northern Sweden during our study. This study showed that the distribution of red foxes was not only influenced by the presence of their main prey (rodents), but also by interactions between alternative prey, altitude, and snow depth. This study also emphasizes the importance of ungulate carcasses for red foxes and for wildlife management.