Bullet Fragments in Deer Remains: Implications for Lead Exposure in Avian Scavengers

Abstract

Bullet fragments in rifle‐killed deer (Odocoileus spp.) carrion have been implicated as agents of lead intoxication and death in bald eagles (Haliaeetus leucocephalus), golden eagles (Aquila chrysaetos), California condors (Gymnogyps californianus), and other avian scavengers. Deer offal piles are present and available to scavengers in autumn, and the degree of exposure depends upon incidence, abundance, and distribution of fragments per offal pile and carcass lost to wounding. In radiographs of selected portions of the remains of 38 deer supplied by cooperating, licensed hunters in 2002–2004, we found metal fragments broadly distributed along wound channels. Ninety‐four percent of samples of deer killed with lead‐based bullets contained fragments, and 90% of 20 offal piles showed fragments: 5 with 0–9 fragments, 5 with 10–100, 5 with 100–199, and 5 showing >200 fragments. In contrast, we counted a total of only 6 fragments in 4 whole deer killed with copper expanding bullets. These findings suggest a high potential for scavenger exposure to lead.

Ammunition is the Principal Source of Lead Accumulated by California Condors Re-Introduced to the Wild

“…Twenty out of the 26 condors sampled in this study (i.e., 77%) possessed blood lead isotope ratios that were consistent with this two end-member mixing model, supporting the hypothesis that the primary sources of lead to released California Condors are low background environmental lead in their diet and elevated levels of lead from ammunition, the latter most likely originating from the inadvertent ingestion of spent ammunition fragments embedded within mammal carcasses and offal piles. Hunted game and other mammals may contain hundreds of lead fragments (41,42), the majority of which are likely to be small (<1 mm), accounting for the condors with moderately elevated blood lead concentrations and an isotope ratio approaching that of ammunition (Figure 1). (38) 0.8403 Sierra Nevada snow fed lake water (38) 0.8453 Northern California urban aerosols (39) 0 (40) a Isotopic values for each diet sample animal (dairy calves, mule deer, sea lion) were determined by analyzing both liver and bone samples from each animal.…”

Feather Lead Concentrations and 207Pb/206Pb Ratios Reveal Lead Exposure History of California Condors (Gymnogyps californianus)

“…Annual or biannual blood lead monitoring will capture only about 5-10% of a bird's annual exposure history. Consequently, establishing comprehensive lead exposure biomarkers for condors as well as other avian species (e.g., eagles (9)) considered at high risk for lead exposure is needed.…”

Lead Bullet Fragments in Venison from Rifle-killed Deer: Potential for Human Dietary Exposure

“…Studies have linked elevated blood lead concentrations of subsistence hunters in northern Canada, Alaska, Greenland, and elsewhere to consumption of shotgun-killed birds [18-25; see 26,27]. The hypothesis that rifle bullet fragments are an additional source of human lead exposure is suggested by radiographic studies of deer killed with standard lead-based bullets, which show hundreds of small metal fragments widely dispersed around wound channels [28][29][30]. The possibility of inadvertent lead contamination in prepared meat consumed by hunters and their families is noteworthy, considering the millions of people who hunt big game in the U.S. [31] and the thousands of deer annually donated to food pantries for the poor [32,33].…”