Parasite diversity and intensity in sympatric arctic and red fox: Implications of Arctic climate change

Background/Question/Methods

Parasites influence entire ecosystems by impacting host population dynamics, energy flow within food webs, and overall biodiversity. Differences in life history, diet, habitat use, and behavior affect each host’s susceptibility to parasites. Arctic fox (Vulpes lagopus) are circumpolar predators whose range overlaps with red fox (Vulpes vulpes) at the southern edge of the arctic tundra. Red fox are known predators and competitors of arctic fox, but parasite transmission is another potential mechanism by which these species may interact. Red fox have one of the largest ranges of any land animal, covering a broad diversity of prey types and climatic conditions and exposing them to high parasite diversity and abundance, and likely have behavioral and physiological adaptations against parasites. In contrast, low biodiversity and harsh conditions in the Arctic likely reduced exposure of arctic fox to parasites during their evolutionary history, but as red fox expand northward with climate warming this exposure could increase. To compare parasite prevalence and intensity in sympatric arctic and red fox we examined fox carcasses collected from local trappers in Churchill, Manitoba, Canada and feces collected from dens, and compared parasite infections to diet estimates from stable isotope and fecal analysis.

Results/Conclusions

Both prevalence and intensity of parasite infections were higher in arctic fox than sympatric red fox. All arctic fox were infected with nematodes (ascarid and ancylostomatidae species) and a cestode, Taenia crassiceps, whereas prevalence of these groups and numbers per host were significantly lower in red fox. Stable isotope ratios of fox hair indicated significant differences in diet. Stable isotope mixing models suggest red fox rely more on snowshoe hares (Lepus americanus), whereas arctic fox consume more collared lemmings (Dicrostonyx richardsoni), an important intermediate host for T. crassiceps, suggesting diet strongly influences the parasite community. Nematodes are frequently transferred through indirect contamination. Red fox defecated on dens in winter significantly less than arctic fox, which may be an adaptive behaviour to reduce nematode infection. The greater parasite infections of arctic fox, whether due to diet or behavior differences, suggest that the warming climate may increase their susceptibility even further through altered intermediate host abundance and milder conditions for free living forms of parasites, as well as increased exposure to red fox. As arctic fox are the primary predator on rodents and ground nesting birds in the Arctic, this increased susceptibility could have cascading effects on many Arctic species.