Researchers solved the mystery behind lead poisoning in endangered African vultures

Solving the mystery behind lead-poisoned scavengers.
Solving the mystery behind lead-poisoned scavengers.
Image: AP Photo/Ricardo Moraes
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Researchers in southern Africa have pieced together an explanation to the mystery of why so many endangered vultures test positive for lead poisoning.

There have been steep declines in the number of vultures across the African continent. In the last 30 years, the eight vulture species there have dropped in number by 62%, according to National Geographic. The story is even worse in India, where the number of vultures has fallen by about 99% in the last 15 years—one of the fastest declines in a species population ever. They’re dying by flying into power lines, wind turbines, being hunted by witch doctors for their body parts, and by eating carcasses contaminated with pesticides—and lead.

In a study published this week (March 14) in the journal Science of the Total Environment, researchers over the course of four years tested nearly 600 critically endangered African White-backed vultures in Botswana and found that a third of them suffered from lead poisoning. “The only logical explanation for the patterns of lead poisoning we observed is if lead bullets were the source of this contamination,” said Beckie Garbett, a PhD student at University of Cape Town, and lead author of the study, in a press release.

According to the paper, when hunters fire upon animals, the lead-based bullets they currently use are shattering inside the shot animals’ bodies, contaminating their blood. Later on, the vultures feast on the corpses of those dead animals, then fly away with high levels of lead in their own systems.

The study supports a new initiative by conservation groups, including Raptors Botswana, to get big game hunters to change the types of bullets they use on hunting expeditions. In the past, similar efforts included a 2014 ban on hunting on government lands, which wound up having no effect on vulture lead poisoning because the scavengers simply followed hunters off public lands where they would be more likely to find carcasses. A widespread shift would be good news for all sorts of natural scavengers, not just vultures. Lead poisoning was also one of the main reasons behind a staggering dip in the California condor population between 1997 and 2011, driving that species dangerously close to extinction. In addition to impacting an individual bird’s health, lead poisoning can also negatively affect reproduction, according to the research.

The loss of winged scavengers has larger implications. They are important players in the food chain because when they eat carcasses, they stop the potential spread of deadly bacterias and fungus. In India, researchers have found a link between the decline in vultures and the spread of deadly diseases such as rabies.