Blood Levels of Different Trace Elements in the Endangered Iberian Lynx (Lynx pardinus) and Their Association with Endogenous and Exogenous Factors

Trace elements are persistent environmental contaminants that can bioaccumulate and biomagnify through food webs, making wildlife valuable sentinels of ecosystem health. This study provides the first characterization of trace element concentrations in whole blood from free-ranging Iberian lynxes (Lynx pardinus) and evaluates the biological and environmental factors influencing their variability, including comparisons with captive individuals. A total of 229 blood samples collected in Extremadura (southwestern Spain) between 2018 and 2024 were analyzed for Cr, Mn, Cu, Zn, As, Se, Cd, Hg, Fe, and Pb. Overall, concentrations were within the ranges reported for other mammalian species, and no clinical evidence of adverse health effects was detected during routine veterinary examinations. Significant correlations were identified among several elements, particularly between Zn and Fe, with moderate associations between Mn and Zn and between Fe and Cu, suggesting common environmental sources and interconnected physiological regulation. Trace element concentrations were significantly influenced by age, sex, geographical area, and sampling period, especially for As and Se, reflecting differences in bioaccumulation, metabolism, and environmental exposure. Principal component analysis revealed a largely shared multielement profile, with no clear separation among populations or biological groups, indicating relatively homogeneous exposure despite moderate spatial and individual variability. These findings provide the first reference values for trace elements in Iberian lynx whole blood, establishing a baseline for biomonitoring, ecotoxicological assessment, and conservation of this threatened felid.