Assessing the risk of lead exposure for the conservation of the endangered Pyrenean bearded vulture (Gypaetus barbatus) population

Abstract

Acute and chronic lead (Pb) poisoning have been recognized as some of the most important causes of mortality for raptors worldwide. We simultaneously examined the recent, medium-term and long-term lead exposure of the endangered bearded vulture (Gypaetus barbatus) from the Pyrenees (northern Spain and southern France). One hundred and one blood samples from 87 captured individuals and tissue samples (liver and bone) from a further 43 dead individuals were analyzed for lead residues. The majority of individuals examined had very low lead concentrations in blood, liver and bone. However, two individuals showed elevated blood Pb levels, two individuals showed liver lead concentrations indicative of excessive lead exposure and one individual showed bone lead levels indicative of chronic lead poisoning, suggesting that the Pyrenean population is not free from the risk of poisoning. We found that Pb exposure was significantly higher in adult individuals as well as in the northern (France) and eastern (Catalonia) range of their distribution. These differences could be related to different feeding habits between age classes (pre-adults are more linked to supplementary feeding sites) and differences in hunting practices between regions (in some regions, carcasses and offal of game animals are not retrieved). Blood, liver and bone lead levels found were slightly higher during the hunting season than outside of the hunting season. Lead presents an unnecessary threat to adult birds and the only way to remove this risk is to ban all hunting with lead within the range of distribution of the endangered bearded vulture. Acute and chronic lead poisoning should be considered in differential diagnosis in any diseased or injured wild bearded vulture, especially subadult and adult individuals, and the potential risk of Pb poisoning should be considered in future reintroduction programs.