Developmental Differences in the Organ-Specific Distribution of Cu, Zn, Cd, and Pb in Free-Ranging Wild Boar (Sus scrofa).

Wild boar (Sus scrofa) have been used as sentinel species for monitoring environmental metal contamination; however, developmental variation in internal metal distribution remains poorly understood in free-ranging wildlife. Here, we investigated organ-specific distribution patterns of copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) by explicitly comparing fetal and non-fetal wild boar collected in western Japan. A total of 13 individuals, including eight fetuses from two pregnant females, the two pregnant females, one adult male, and two juveniles, were analyzed. Metal concentrations were determined in muscle, heart, liver, kidney, and femur using ICP-MS, and relative organ distributions were evaluated using non-metric multidimensional scaling and permutational multivariate analysis of variance. Developmental differences were apparent for Cu, Cd, and Pb, whereas Zn exhibited stable distribution patterns across stages, suggesting maintained physiological regulation. Fetal individuals showed pronounced hepatic enrichment of Cu, reflecting active placental transport and developmental hepatic storage. In contrast, Cd displayed renal dominance exclusively in non-fetal individuals, indicating postnatal accumulation, while Pb showed relatively greater femoral contributions in non-fetal individuals despite low absolute concentrations. Together, these results suggest that multi-organ distribution patterns provide useful insight into developmental metal partitioning beyond absolute concentration data and highlight the importance of incorporating developmental context into ecotoxicological assessments of free-ranging wildlife under natural exposure conditions.