We also found that black bears (Ursus americanus), golden eagles and bald eagles (Aquila chrysaetos and Haliaeetus leucocephalus, two species of conservation concern) scavenged heavily on moose viscera left by hunters. The isotope signature of the lead detected in contaminated ravens tended towards the signature from lead ammunition. Non-contaminated birds exhibited no ammunition isotope signatures. Lead concentration was twice as high in one year compared to the other, matching the number of rifle-shot moose in the area.

Using a contamination threshold of 100 µg x L(-1), more than 50% of individuals were lead-contaminated during the moose hunting period. Blood lead concentration in ravens increased over time, indicating lead accumulation over the moose-hunting season. Finally, we identified the different scavenger species that could potentially be exposed to lead by installing automatic cameras targeting moose gut piles. The source of the lead contamination was also determined using stable isotope analyses. For two consecutive years we quantified the level lead exposure in individuals of a sentinel scavenger species, the common raven (Corvus corax), captured during the moose (Alces alces) hunting season in eastern Quebec, Canada.

A potential source of lead poisoning in wild animals, and especially in scavengers, results from the consumption of ammunition residues in the tissues of big game killed by hunters. Lead accumulation can induce severe disorders and alter survival both in mammals (including humans) and in birds. Top predators and scavengers are vulnerable to pollutants, particularly those accumulated along the food chain.

Instal Danger Scavenger