The сontent of mercury in the tissues of amphibians from Northwest Russia (Vologda region) varies within 0.001 to 0.370 mg/kg wet weight. The average values of Hg сontent in the organs and tissues of studied amphibian species decrease in the order: liver > kidneys > heart > intestines > muscles > skin. The mercury сontent in the tissues of genus Pelophylax is higher than that in the tissues of samples of genus Rana and species Bufo bufo. The сontent of mercury in the tissues of Rana spp. collected in the Western part of the Vologda region is significantly higher than that in samples from the Eastern part.

Twenty-three red foxes (Vulpes vulpes L.) were tested for the presence of mercury in their internal organs. These animals were captured in the Vologda region (Northwest Russia) within 2009 and 2018. The animal's liver, kidneys, muscles, brain, spleen, chyme and intestinal wall were tested. The concentrations level ranged between 0.001 mg/kg of wet mass in the chyme and the brain-up to 0.713 mg/kg of wet mass in kidneys. There is a strong correlation between the concentrations of mercury in separate pairs of tissues of a red fox. The ratio of concentrations of mercury between the tissues of the red fox was discovered: the concentration of mercury in the brain was 2 to 18 times lower than in other tissues.