Highlighting the risk of environmental lead contamination for deer management in Australia

Lead-based bullets used to shoot deer typically fragment. These toxic fragments are a threat to wildlife scavengers and human consumers of venison. Awareness of this issue is widespread internationally but limited in Australia. The aim of this research was to characterise deer carcass contamination via bullet fragmentation associated with lead-based and lead-free ammunition in a deer culling program conducted in Australia. We used radiography (X-rays) to study Hog Deer (Axis porcinus) shot in a professional ground-based shooting program in Victoria, south-eastern Australia. Our data captured 33 deer shot with frangible lead-based bullets in 2021, and 21 deer shot with monolithic lead-free (copper-based) bullets from the same rifles in 2021–2022. For lead-based bullets, the mean number of lead fragments per carcass ranged from seven to 629 (mean ± SD = 256 ± 169), mean fragment size was 1.2 mm² (74% of fragments were <1.0 mm²) and the mean fragment coverage area (the smallest ellipse covering all fragments) was 325 cm². Of these deer, 36% had metallic fragments in the ‘back strap’ (loin) muscles and 42% had metallic fragments in the shoulder muscles: meat cuts typically removed for human consumption. In contrast, for lead-free bullets, the mean number of metallic fragments per carcass ranged from zero to four (0.5 ± 1.0), with only 29% of carcasses having any fragments, and no deer had metallic fragments in the loin or shoulder muscles. On the basis of these results, it is clear that lead-based bullets used for shooting deer in Australia pose risks to wildlife scavengers, and to human consumers when used in hunting. Australian wildlife managers involved in mitigating deer impacts should strongly consider a timely transition to lead-free bullets.