Geochemical landscapes as drivers of trace and toxic element profiles in wild red deer (Cervus elaphus).

Tissue concentrations of essential trace and toxic elements in red deer (Cervus elaphus) are associated with the plants, soil and water they ingest. As such, variation in tissue concentrations is associated with variation in local geochemistry and bioavailability of elements. Physiological factors such as liver fluke (Fasciola hepatica) infection, breeding status, and in-tissue element interactions may also affect tissue concentrations, though their effects in red deer are not well understood. The primary objective of this study was therefore to survey wild red deer liver element concentrations across a range of geographically distinct populations during the Scottish red deer stalking season; and, in so doing, establishes element reference ranges while also exploring geographic and temporal variation and physiological factors. Livers were sampled from carcasses intended for human consumption on nine hunting estates during two seasons (2012-13, 2013-14). Samples were digested and analysed by ICP-OES for essential trace elements (Co, Cu, Fe, Mn, Mo, Se, Zn) and for Cd. Data (n=787) were modelled against cull location, date, and F. hepatica diagnosis. Interactions between elements within liver, and differences in element profiles between estates, were explored by principal component analysis. Our results revealed marked geographic variation in Cd, Cu and Se, where up to four-fold differences in median element concentrations occurred between estates, and, in males, Mn, Mo and Zn declined as the breeding season approached. In both sexes, within-liver associations (Cd-Cu-Se and Mn-Mo-Zn) were found. In females, liver Zn was greater on average in individuals that were not infected with F. hepatica. This study is the first to quantify geographic variation in Scottish red deer liver element concentrations; the drivers of which remain to be explored (and may be management related), and, the consequence of which may affect sub-clinical health.