Whole blood selenium concentrations in four free-ranging mammal species from central Scandinavia

Background Selenium (Se) is an essential element for mammals, with a relatively narrow safety margin between deficiency and toxicity. It is involved in the function of many vital activities and systems, including antioxidants, immune system, thyroid activity, muscle metabolism, and growth by composing different proteins and enzymes. Northern Europe is a Se deficient region, and livestock have been supplemented with mineral bolus or similar for decades to counteract Se deficiency, whereas Finland even adds Se to fertilizers to supplement soil, plants, animals and humans. Relatively few studies have investigated total Se concentrations ([TSe]) in wildlife, and here we present [TSe] measured in whole blood in moose (Alces alces), brown bears (Ursus arctos), wolves (Canis lupus), and wolverines (Gulo gulo) from Norway and Sweden. Results [TSe]hole blood increased with the trophic level of the species: herbivorous moose < omnivorous bears < carnivorous wolves < scavenging wolverines. Compared to established reference ranges of [TSe] in domesticated species, more than half of all moose sampled and 5% of brown bears were Se deficient. Surprisingly, 49% of bears, 42% wolves and 29% wolverines had [TSe] above recommended references range for domesticated species. In general, [TSe] significantly increased with age and body weight in all sampled species, whereas for most species, there was an additional association with region, year, and season sampled, reflecting variations in Se uptake caused by the element's geochemical properties related to bedrock and soil availability and atmospheric precipitation. Conclusions Further studies should focus on a wider spatial distribution for these animals and especially include more wolverines to investigate the relatively high [TSe] observed in this species. We also emphasize the importance of measuring Se in poor regions for ecotoxicology studies, since Se deficiency can exacerbate heavy metal toxicosis.