Anthropogenic food use and diet overlap between red foxes (Vulpesvulpes) and arctic foxes (Vulpeslagopus) in Prudhoe Bay, Alaska

Abstract

Red foxes (Vulpes vulpes (L., 1758)) recently expanded into the oil fields at Prudhoe Bay, Alaska, USA, and we hypothesized that the availability of anthropogenic foods may contribute to their success and persistence there. This study assessed the importance of anthropogenic foods to the diets of red foxes and arctic foxes (Vulpes lagopus (L., 1758)), and competition for food resources between the two species in Prudhoe Bay. We used stable isotope analysis of fox tissues to infer diet during summer and winter for both red and arctic foxes, and lifetime diet for red fox. While the contribution of anthropogenic foods in late summer for both species' diets was low (~10% to 15%), the contribution in late winter was higher and varied between species (red foxes = 49%; arctic foxes = 39%). Estimates of lifetime diet in red foxes suggest consistent use of anthropogenic foods. We found moderate overlap of fox diets, although red foxes appeared to be more specialized on lemmings, whereas arctic foxes had a more diverse diet. Availability and consumption of anthropogenic foods by red foxes, particularly in winter, may partially explain their year-round presence in Prudhoe Bay.Résumé : Les renards roux (Vulpes vulpes (L., 1758)) se sont répandus récemment dans les champs pétrolifères de Prudhoe Bay, en Alaska, États-Unis, et nous avons postulé que la disponibilité de nourriture de source anthropique pourrait y contribuer à leur succès et leur persistance. L'étude a évalué l'importance de la nourriture de source anthropique dans les régimes alimentaires des renards roux et renards arctiques (Vulpes lagopus (L., 1758)) et la concurrence des deux espèces pour l'obtention de ressources alimentaires à Prudhoe Bay. Nous avons utilisé l'analyse d'isotopes stables de tissus de renard pour déduire les régimes alimentaires estivaux et hivernaux des renards roux et arctiques et le régime alimentaire des renards roux pendant leur durée de vie. Si la contribution de nourriture de source anthropique à la fin de l'été aux régimes alimentaires des deux espèces était faible (de~10 % à 15 %), elle était plus élevée à la fin de l'hiver et variait selon l'espèce (renards roux = 49 %; renards arctique = 39 %). Les estimations du régime alimentaire sur la durée de vie des renards roux semblent indiquer une utilisation soutenue de nourriture de source anthropique. Nous avons noté un chevauchement modéré des régimes alimentaires des renards, les renards roux semblant toutefois avoir un régime plus spécialisé axé sur les lemmings, alors que le régime des renards arctiques était plus varié. La disponibilité et la consommation de nourriture de source anthropique par les renards roux, en hiver plus particulière-ment, pourraient en partie expliquer leur présence à l'année à Prudhoe Bay. [Traduit par la Rédaction] Mots-clés : Vulpes vulpes, Vulpes lagopus, renard roux, renard arctique, plaine côtière de l'Arctique, écologie des perturbations, modèle de mélange d'isotopes stables, concurrence interspécifique.

Disentangling the relative influences of global drivers of change in biodiversity: A study of the twentieth‐century red fox expansion into the Canadian Arctic

“…Presence of sedentary sites in a given region was used as an indicator of anthropogenic food subsidies available to foxes. Cockburn (), Gagnon () and Qikiqtani Inuit Association () support our premise that the appearance of focal points of human activity in northern Canada resulted in the creation of garbage dumps, which are often used by predators (Eberhardt, ; Savory et al, ).…”

“…In addition, settlements were well within reach of each other for red foxes, given their dispersal abilities (Storm et al, ; Walton, Samelius, Odden, & Willebrand, ). Field studies showed that subsidies can influence resource selection by predators (Bino et al, ; Giroux et al, ; Savory et al, ) and increase their survival, fitness (Bino et al, ; Craighead, Sumner, & Mitchell, ; Pons & Migot, ) and abundance (Montagano, Leroux, Giroux, & Lecomte, ). However, we know little about the quantity of density‐independent resources necessary to cause numerical responses in predators (but see Montagano et al, ; Persson, ).…”

Emergent Rainy Winter Warm Spells May Promote Boreal Predator Expansion into the Arctic

“…In other areas of the Arctic, however, red and Arctic fox populations have been stable over several decades despite pronounced climate warming (Gallant et al, 2012), which indicates that increased primary production did not necessarily favor red foxes. Other evidence suggests that resource subsidies in winter, which are often provided by human activity, have played a decisive role for the growth of red fox populations in tundra areas in northern Fennoscandia (Kaikusalo and Angerbjörn, 1995;Killengreen et al, 2011) and Alaska (Savory et al, 2014;Stickney et al, 2014). Although little is known about the expansion of corvids into the Arctic, anthropogenic resources appear to be important as well (Restani et al, 2001).…”

Trophic structure in a rapidly urbanizing planet

“…However, there are few direct experimental tests of this hypothesis, and existing tests show variation among taxa and cities (Rodewald & Shustack, ; West & Peery, ). It is also unclear how diet relates to the fitness of synanthropic species (Moss, Alldredge, & Pauli, ; Savory, Hunter, Wooller, & O'Brien, ). Despite their abundance, urban exploiters commonly show signs of physiological stress as well as having high pollutant concentrations in their tissues (Bauerová et al., ; Strasser & Heath, ).…”

“…The association between generalist feeding and urbanization might also be spurious, because generalist feeding is often correlated with other traits that could influence urban tolerance (such as toxin resistance, plastic social and dispersal behaviours) (Bateman & Fleming, 2012;Kark, Iwaniuk, Schalimtzek, & Banker, 2007;Marzluff, 2017;Sol, Lapiedra, & González-Lagos, 2013 (Rodewald & Shustack, 2008;West & Peery, 2017). It is also unclear how diet relates to the fitness of synanthropic species (Moss, Alldredge, & Pauli, 2016;Savory, Hunter, Wooller, & O'Brien, 2014). Despite their abundance, urban exploiters commonly show signs of physiological stress as well as having high pollutant concentrations in their tissues (Bauerová et al, 2017;Strasser & Heath, 2013).…”