Study Shows Lead From Hunters in African White-Backed Vultures' Blood

If even the hardiest scavengers can't make it, who can?

When we think about vultures, our mind’s eye may picture garbage eaters — birds feasting on festering carcasses. As the garbage eaters of the natural world, it might make sense that they’d be able to survive longer than other species since there’s so much for them to pick on. After all, as long as death exists, vultures will have dead animals to eat. But new research published Wednesday on a population of African vultures suggests that the future for these scavengers may also be bleak.

In a paper published Wednesday in the journal Science of the Total Environment, an international team of researchers found that African white-backed vultures (Gyps africanus) living in Botswana had elevated levels of lead in their bloodstreams during hunting season in areas where people hunted. Ornithologists suspect that the lead found in the vultures comes from the remains of animals killed by hunters, as lead bullets tend to shatter and scatter into the bodies of their victims.

Researchers sampled vultures and found that they had elevated levels of lead in their blood during hunting season.

Raptors Botswana

To conduct the study, led by Beckie Garbett, a Ph.D. student at the University of Cape Town, researchers took blood samples from almost 600 African white-backed vultures in Botswana over four years. Their results, which showed a correlation between hunting season, hunting areas, and lead concentrations in vultures’ blood, painted a pretty clear picture.

“The only logical explanation for the patterns of lead poisoning we observed is if lead bullets were the source of this contamination,” says Garbett in a statement.

Lead ammunition is banned for certain types of bird hunting in the U.S., and the researchers hope that this study will help vulture conservation efforts.

Beckie Garbett

The International Union for Conservation of Nature classifies African white-backed vultures as “critically endangered,” and while poachers and poorly-aimed shots from hunters have long posed the most immediate threat to vultures, this research suggests that lead may be equally urgent. Birds are extremely sensitive to lead poisoning, and lead can persist for a long time in the environment.

Since lead is a highly toxic metal associated with brain damage, the U.S. Fish and Wildlife Service banned its use in hunting waterfowl in wildlife refuges in 1991, as well as the use of lead fishing tackle — often used for fishing weights, since the flexible metal is easy to clamp on a fishing line. This ruling was overturned in 2017 by Interior Secretary Ryan Zinke, though, which means that birds in the U.S. may face similar dangers as their African cousins.

African white-backed vultures are listed as "critically endangered" by the International Union for Conservation of Nature.

Beckie Garbett

“We were all shocked by how widespread lead poisoning was for this population and just how clearly these elevated levels were associated with recreational hunting activity,” Arjun Amar, Ph.D., associate professor of avian conservation biology at the University of Cape Town and one of Garbett’s co-authors, said in a statement.

While this study is bad news for the African white-backed vulture, it’s not exactly new news that lead ammunition is bad for birds. In 2006, researchers published a paper in the Wildlife Society Bulletin directly linking lead fragments to the decline of the California condor, another bird that unintentionally eats the toxin while feasting on carrion.

And even though U.S. lawmakers haven’t seemed to learn from the lessons of the past, perhaps lawmakers in Botswana and other southern African nations that the African white-backed vultures call home will listen to the advice of the scientific community and require that hunters only use non-lead ammunition in the future. Come on, y’all: Do it for the birds.

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