Assessing contributions from big-game hunting to lead (Pb) ingestion by Canadian wildlife scavengers

Annual harvests of big-game animals taken with lead (Pb) ammunition across Canada, and the contiguous US states were derived to determine the numerical and geographic extent of Pb ingestion risk to scavenging wildlife. Data on Pb bullet fragmentation and contamination of discarded entrails were used to assess the ingestion risk to scavengers. Magnitude, level of ingestion risk, and responsible jurisdiction for this annual Pb exposure were defined. In 2023–2024, 383 402 animals were harvested with Pb-based bullets in Canadian provinces and territories, and 1711 508 in 12 states bordering Canada. An estimated 0.84 g of Pb from one representative 0.300 caliber bullet would be available to scavengers from one gut pile. This constitutes a large, annual, Pb ingestion risk to scavenging wildlife across Canada and the US states. Bald ( Heliaeetus leucocephalus) and golden eagles ( Aquila chrysaetos) could be repeatedly Pb-exposed in Canada and the USA through two major toxic Pb ingestion traps along the western and eastern migratory flyways. Raptors in prairie regions may ingest Pb from discarded carcasses of prairie rodents shot with highly fragmenting bullets. Black bears ( Ursus americanus) are an important Canada-wide scavenger that feeds on hunted animal remains. Non-Pb ammunition use would prevent this annual toxic risk to scavenging species.