Scavenger community structure along an environmental gradient from boreal forest to alpine tundra in Scandinavia

Scavengers can have strong impacts on food webs, and awareness of their role in ecosystems have increased during the last decades. In our study, we used baited camera traps to quantify the structure of the winter scavenger community in central Scandinavia across a forest-alpine continuum and assess how climatic conditions affected spatial patterns of species occurrences. Canonical correspondence analysis revealed that the main habitat type (forest or alpine tundra) and snow depth were main determinants of community structure. According to hierarchical modelling of the species community, species richness was higher in forest than in alpine habitat but was only weakly associated with temperature and snow depth. However, we observed stronger and more diverse impacts of these covariates on individual species. Occurrence at baits of habitat generalists (red fox, golden eagle and common raven) typically increased at low temperatures and high snow depth, probably due to increased energetic demands and lower live prey availability in harsh winter conditions. On the contrary, occurrence of forest specialists (e.g. Eurasian jay) tended to decrease in deep snow, which is possibly a consequence of reduced bait detectability and accessibility. In general, the influence of environmental covariates on species richness and occurrence was lower in alpine tundra than in forests, and habitat generalists dominated the scavenger communities in both habitat types. Following forecasted climate change, altered environmental conditions is likely to cause range expansion of boreal species and range contraction of typical alpine species such as the arctic fox. Our results suggest that altered snow conditions will be a main driver of change.