Abstract
Predatory and scavenging birds are at risk of lead exposure when they feed on animals injured or killed by lead ammunition. While lead ammunition has been banned from waterfowl hunting in North America for almost two decades, lead ammunition is still widely used for hunting big game and small game animals. In this study, we evaluated the association between big game hunting and blood lead concentration in an avian scavenger species that feeds regularly on large mammals in California. We compared blood lead concentration in turkey vultures within and outside of the deer hunting season, and in areas with varying wild pig hunting intensity. Lead exposure in turkey vultures was significantly higher during the deer hunting season compared to the off-season, and blood lead concentration was positively correlated with increasing wild pig hunting intensity. Our results link lead exposure in turkey vultures to deer and wild pig hunting activity at these study sites, and we provide evidence that spent lead ammunition in carrion poses a significant risk of lead exposure to scavengers.
Highlights
Lead poisoning was recognized as an important cause of mortality in wildlife in the late 1950s [1,2,3] when ingested spent lead ammunition and fishing sinkers were linked to significant dieoffs in waterfowl [4]
Age classifications were collapsed into two categories, HY vultures and after hatch year (AHY), vultures given that median blood lead concentrations did not differ between second year vultures and adults
The prevalence of elevated blood lead exposure in vultures sampled during the deer hunting season was 76% (26/34, 95% CI = 60%–88%), which was significantly higher than the 36% prevalence among vultures sampled outside of the deer hunting season (14/39, 95% CI = 22%–51%)
Summary
Lead poisoning was recognized as an important cause of mortality in wildlife in the late 1950s [1,2,3] when ingested spent lead ammunition and fishing sinkers were linked to significant dieoffs in waterfowl [4]. A major impetus for this policy change was mortality in the endangered bald eagle (Haliaeetus leucocephalus) population due to secondary lead poisoning from feeding on waterfowl containing lead ammunition [6,7,8]. While this regulation had a major impact on decreasing lead-associated mortality in waterfowl [9], there was no change in the prevalence of lead poisoning in eagles admitted to a rehabilitation center in the Midwestern U.S during the post-ban period from 1991–1995. Old and new world vultures may be at increased risk of lead exposure because of their unique feeding ecology as obligate scavengers
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