Wolf hair for biomonitoring arsenic, selenium, cadmium and lead exposure: a comparative study with internal organs.

Potentially toxic elements (PTEs) are persistent environmental contaminants with important implications for wildlife health. This study assessed hair as a non-invasive biomonitoring matrix in the Iberian wolf (Canis lupus signatus) by comparing arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb) concentrations in hair, liver, and kidney, and evaluating age-related accumulation patterns. A total of 77 wolves from Northwestern Spain were analysed using inductively coupled plasma mass spectrometry (ICP-MS). Selenium showed the highest concentrations, particularly in kidney and liver, while lower levels in hair reflected preferential accumulation in metabolically active tissues. Arsenic concentrations exceeded background thresholds in liver and kidney and were markedly higher in hair, consistent with excretory processes. Cadmium accumulated mainly in the kidney, indicating chronic low-level exposure, whereas lead concentrations were higher in hair than in liver or kidney, suggesting that hair may serve as a useful non-invasive indicator of Pb exposure in wolves. Age-related patterns varied among elements. Cadmium increased significantly with age in hair, but only when comparing youngest and oldest animals (p < 0.01), consistent with its long biological half-life. In contrast, As was higher in pups when compared to adults (p < 0.05), which could reflect combined effects of developmental physiology and maternal exposure pathways. Selenium showed age-related differences only in liver, while lead exhibited no significant variation. Strong positive correlations were observed between liver and kidney concentrations of As, Cd, and Pb (p < 0.001), whereas relationships between hair and internal organs were weak or absent, indicating that hair provides limited information on internal metal burdens in Iberian wolves. Therefore, further studies are required to evaluate the utility of hair as a complementary biomonitoring matrix suitable for large-scale environmental surveillance and exposure assessment.