![]() ![]() 2014) when the availability of prey is lower (Cagnacci et al. Red foxes are facultative scavengers, and ungulate carrion is often an important part of their diet, especially during winter (Jędrzejewski and Jędrzejewska 1992 Killengreen et al. Species of facultative scavengers in northern ecosystems often utilize carrion during winter, creating possibilities for food web interactions between species that otherwise have weak connections in these ecosystems (Ims and Fuglei 2005). Moreover, red foxes might benefit from increased availability of anthropogenic food resources through the expansion of human settlements, cabin areas, and infrastructure (Gallant et al. Additionally, land use changes have increased areas of crop production and clear-cuts in the forests which, in turn, benefits small rodents and roe deer ( Capreolus capreolus), which are important food resources for the red fox (Pasanen-Mortensen et al. For example, top-down regulation of red foxes has probably been reduced, both due to intense lethal control of large carnivores and reduced hunting pressure from humans (Selås and Vik 2006 Pasanen-Mortensen et al. In Fennoscandia, both direct and indirect factors connected to anthropogenic activity have been linked to red fox range expansion and increased abundance. Increasing and expanding populations of red fox raise concern, as they may negatively affect both populations of endangered species and important game species (Fletcher et al. 2008), and it is listed among the 100 most invasive species outside its original range (Lowe et al. The red fox is a generalist predator occupying a wide range of ecosystems around the globe (Schipper et al. Subsidies can therefore alter predator population dynamics, with consecutive effects on prey populations (Newsome et al. Generalist predators may depend on resource subsidies in periods when their primary prey species are less abundant, less vulnerable, or unavailable (Pereira et al. Such subsidies can cause an increase in abundance and distribution of opportunistic species which, in turn, may result in trophic cascades altering communities, or ecological processes such as competition and predator-prey interactions (Tylianakis et al. 1997 Leroux and Loreau 2008), or by anthropogenic activity (Oro et al. In marginal alpine areas, a numerical response to higher availability of rodents possible lead to the increase in bait visitation the proceeding winter, while in more productive forest areas, low availability of rodents induced a functional diet shift towards scavenging.Įcosystems are subsidized to a varying degree with energy, matter, and organisms from neighboring sources (Polis et al. In this study, we showed that small rodent dynamics influenced red fox scavenging, at least in winter, but with contrasting patterns depending on environmental conditions. Scavenging patterns by red fox on the pulsed but predictable food resource from hunting remains in the autumn revealed no patterns throughout the rodent cycle. Contrastingly, red fox use of baits in the forest was highest during rodent low phase, and when snow was deep, indicating a higher dependency of carrion under these conditions. This probably reflected relatively higher red fox abundance due to increased reproduction or migration of individuals from neighboring areas, possibly also enhanced by a diet shift. In alpine areas, use of baits was highest post rodent peaks and when snow depth was low. We found contrasting patterns of scavenging between habitats during winter. In this study, we used cameras on bait stations and hunting remains to investigate how spatiotemporal patterns of red fox scavenging were influenced by abundance and accessibility of live prey, i.e., small rodent population cycles, snow depth, and primary productivity. Concern has been raised regarding red fox ( Vulpes Vulpes) population increase and range expansion into alpine tundra, directly and indirectly enhanced by human activities, including carrion supply, and its negative impact on native fauna.
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