Lead toxicity in wildlife
Lead is a highly toxic heavy metal that is found in many types of ammunition and fishing tackle. Wild birds can become toxicity-prone when they accidentally consume a source of lead through their normal feeding habits. Ingestion of lead from spent hunting ammunition or fishing tackle can cause illness or death in wild birds. Death from lead toxicity has been documented in Wisconsin in bald and golden eagles, common loons, trumpeter swans, turkey vultures, waterfowl and a whooping crane.
TRANSMISSION
Eagles can accidentally eat lead fragments found in the gut piles and carcasses of deer harvested with lead ammunition. Loons pick up small pebbles from the bottom of lakes as a part of their normal behavior to add grit to their crop (the upper part of their digestive tract) and frequently mistake lead fishing weights for small stones. Trumpeter swans feed by stirring up the bottom of lakes and accidentally eat lead fishing weights or spent lead shot pellets. The consumed lead breaks down in the stomach and is transported through the blood. The lead is then absorbed into the liver, kidney and bone tissues.
CLINICAL SIGNS
Birds exposed to sudden high levels of lead can die suddenly without signs. Birds that suffer from slow, longer-term exposure to lead can show signs of weakness, loss of muscle mass and fat reserves, green diarrhea, incoordination, paralysis or convulsions. Long-term effects of lead exposure can alter bird behavior and survival of birds.
DISEASE MANAGEMENT
In 1991, the US Fish and Wildlife Service launched a nationwide ban on lead shots for waterfowl hunting to reduce the number of lead shots falling into lakes. Since the inception of dove hunting in Wisconsin in 2003, the Department has prohibited the use of lead shots for hunting mourning doves on state-managed lands since the inception of dove hunting in Wisconsin in 2003.
Hunters wanting to help reduce the loss of wildlife from lead toxicity can switch from using lead ammunition to non-toxic ammunition for all their hunting activities. People who fish can purchase non-lead fishing tackle and dispose of their lead tackle by taking it to a recycling facility that accepts and properly disposes of lead. Other wildlife enthusiasts can help by sharing information with their family and friends on the dangers of lead to wildlife.
PUBLIC HEALTH
Deer harvested with lead bullets has been shown to have tiny lead particles or fragments remaining in the processed meat. Some of the lead fragments found in venison samples were far from the wound channel and were too small to see during processing. Although research has not linked lead in venison to human health effects, tests on processed venison suggest some samples may have levels of concern.