Abstract
Changes in concentration of pollutants and pathogen distribution can vary among ecotypes (e.g. marine versus terrestrial food resources). This may have important implications for the animals that reside within them. We examined 1) canid pathogen presence in an endangered arctic fox (Vulpes lagopus) population and 2) relative total mercury (THg) level as a function of ecotype (‘coastal’ or ‘inland’) for arctic foxes to test whether the presence of pathogens or heavy metal concentration correlate with population health. The Bering Sea populations on Bering and Mednyi Islands were compared to Icelandic arctic fox populations with respect to inland and coastal ecotypes. Serological and DNA based pathogen screening techniques were used to examine arctic foxes for pathogens. THg was measured by atomic absorption spectrometry from hair samples of historical and modern collected arctic foxes and samples from their prey species (hair and internal organs). Presence of pathogens did not correlate with population decline from Mednyi Island. However, THg concentration correlated strongly with ecotype and was reflected in the THg concentrations detected in available food sources in each ecotype. The highest concentration of THg was found in ecotypes where foxes depended on marine vertebrates for food. Exclusively inland ecotypes had low THg concentrations. The results suggest that absolute exposure to heavy metals may be less important than the feeding ecology and feeding opportunities of top predators such as arctic foxes which may in turn influence population health and stability. A higher risk to wildlife of heavy metal exposure correlates with feeding strategies that rely primarily on a marine based diet.
Highlights
Ecotype differences can have profound impacts on organismal adaptation and long term survival
There was no significant difference between the average levels of the THg in arctic foxes originating from the Commander Islands and Iceland coastal populations (Tukey-Kramer post-hoc test, all P.0.05), while those from the Iceland inland ecotype had a significantly lower average heavy metal concentration compared to the other three populations (P,0.05) (Table 2, Figure 2)
Iceland represents two ecotypes with inland foxes feeding primarily on small land mammals and birds and coastal foxes which have a similar diet to Mednyi Island foxes with the difference being that they can migrate to the inland ecotype
Summary
Ecotype differences (e.g. food resources, predator-prey or hostpathogen interactions) can have profound impacts on organismal adaptation and long term survival. Part of that environment includes pathogens and pollutants which in the case of pathogens can suddenly emerge and in the case of pollutants increase in concentration rapidly and disperse throughout the food chain. In addition to their clinical effects, pollutants can cause immune suppression which can exacerbate the effect of infection even for normally low or non-pathogenic microorganisms. These effects can be further aggravated by climate change causing energetic stress associated with low food accessibility and starvation, resulting in population decline. Determining the distribution of pathogens and pollutants among ecosystems are critical to identifying threats to population and species health
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