Lead levels in Eurasian otters decline with time and reveal interactions between sources, prevailing weather, and stream chemistry.

The uptake of contaminants by biota varies spatially and temporally due to a complex range of interacting environmental variables, but such complexities are typically disregarded in studies of temporal change. Here, we use linear modeling to explore spatial and temporal variation in bone Pb levels measured in samples taken from 329 Eurasian otters (Lutra lutra) found dead in southwest England. Between 1992 and 2004 Pb levels in otters fell by 73%, following UK legislative control of Pb emissions implemented since the mid 1980s. Spatial variation in bone Pb was positively correlated with modeled Pb emissions and stream sediment Pb, which interacted negatively with wind-speed and sediment Ca, respectively. Opportunistic collection of samples from wildlife mortalities provided a valuable opportunity for monitoring environmental contamination, interpretation of which was aided by spatially explicit analysis of environmental variables.