Highways associated with expansion of boreal scavengers into the alpine tundra of Fennoscandia

1. Habitat fragmentation may affect species distributions through, for example, altered resource availability and shifts in species interactions. Fragmentation by roads has had negative impacts on Fennoscandian alpine ecosystems, with reduction of habitats and connectivity for alpine species. Concurrently, infrastructure development causes influx of subsidies through roadkills and litter, which may facilitate expansion of boreal scavenging species, such as the red fox Vulpes vulpes, which may intensify negative interactions with alpine species. Hence, understanding the impact of subsidies within marginal alpine areas is imperative for successful conservation and management of particularly vulnerable alpine species. 2. We used snow tracking and camera traps in three alpine tundra areas in Norway to investigate whether the presence of boreal scavengers was positively associated with highways during winter, and if this contrasted the pattern of a critically endangered alpine species, the Arctic fox Vulpes lagopus. In summer, artificial nests were used to assess whether predation risk was related to proximity to highways. 3. During winter, the occurrence of red foxes was higher close to highways and decreased with increasing distance to highways, while the arctic fox showed no discernible pattern. Red fox occurrence increased with the number of edible items of anthropogenic origin located along highways, whereas arctic fox occurrence decreased. 4. The overall predation risk of artificial nests during summer was high (>31.2%) and increased with proximity to the highway in the area with highest traffic volume. 5. Synthesis and applications. Highways crossing alpine areas may attract boreal scavengers, possibly connected to increased access to subsidies of anthropogenic origin. Litter and food waste dominated available subsidies along highways in our study, and prevailing mitigating measures directed at reducing roadkill and movement restrictions may not be applicable to reduce negative effects of littering. We recommend actions focusing on informational campaigns, improved garbage disposal facilities and routines, and imposing fines for littering, to reduce negative impacts on vulnerable species. This is likely needed to achieve goals of ‘no impact’ from the physical loss of habitats due to road development