Evaluating trace elements as a conservation concern for Eurasian lynx (Lynx lynx) in Switzerland

The Eurasian lynx, an endangered species in Switzerland, faces major threats including traffic collisions, illegal killing, and low genetic diversity. However, the impact of trace element (TE) exposure on its conservation remains poorly understood. As a top predator primarily feeding on game species, this felid can be exposed to non-essential TEs, including lead and mercury, which can be toxic even at low concentrations. In addition, overexposure to or deficiency of essential TEs such as copper or zinc can cause adverse health effects. To address this gap, we analysed liver samples from 122 individuals archived in the Swiss national health surveillance program by measuring the concentrations of eight TEs: four non-essential TEs (arsenic, cadmium, lead, and mercury) and four essential TEs (copper, iron, selenium, and zinc). Concentrations were consistent with those reported in other free-ranging Lynx populations and remained below toxicity thresholds reported for mammals, while also being above deficiency levels for essential TEs. They varied with age for some TEs, but not with sex, time or environmental variables. Additionally, we used a body condition score to examine the relationship between TE concentrations and Eurasian lynx health. Lower body condition scores were associated with higher concentrations of both non-essential and essential TEs, likely reflecting poor health affecting TE accumulation rather than a direct toxic effect. Overall, our study suggests that the current TE exposure does not significantly threaten Eurasian lynx populations in Switzerland, providing new insights for conservation efforts and long-term health monitoring.