Effects of contaminants on terrestrial mammals
There is concern for how contaminants affect the Arctic fox in periods when foxes are starving or females are suckling.
The fat reserves of Arctic foxes change dramatically through the year, making them especially vulnerable because contaminants stored in adipose tissue may be liberated when the fat stores are burnt. Large, natural, annual fluctuations in the storing of body fat mean that toxins may be liberated from adipose tissue in the form of lipids to internal organs like the liver and brain. The highest level of lipids, over 20 %, is attained in November-December and it is reduced during the spring to a minimum of 6 % in summer. The Arctic fox also experiences extreme variations in its fat reserves through the winter in periods when food is in short supply.
Animals that are in good health have been found to have lower levels of contaminants than unfit ones. Arctic foxes have little body fat when they are experiencing a comparatively high degree of physiological stress in the breeding season in spring and summer, and in periods when they are hungry in winter.
We know very little about the effects the high levels of contaminants have on, for example, a suckling mother and her cubs, or a fox that cannot find food and has to burn its lipid reserves in winter. An impairment of their immune system has been found in sledge dogs in Greenland after they have been fed whale blubber containing high levels of contaminants. It is therefore likely that the current high level of contaminants may have negative effects on the immune and reproductive systems of the Arctic fox.