A new study has revealed disturbing reasons why White-backed vulture chicks are ingesting deadly amounts of lead.
The study, conducted by BirdLife South Africa, the University of the Witwatersrand and the University of Johannesburg, and funded by the Isdell Family Foundation and Mary Oppenheimer & Daughters Foundation, took blood samples from chicks at Dronfield Nature Reserve in the Northern Cape.
The samples were used to quantify the isotopic signatures of lead.
The vultures of Dronfield, located close to Kimberley, form one of the country’s most important White-backed vulture colonies.
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Where does the lead come from?
Vulture project manager at BirdLife South Africa, Linda van den Heever, said the results of the study allowed an array of potential lead poisoning sources to be excluded.
This includes lead from mining, industrial activity, coal, air, water and soil, and lead that could have lingered from leaded fuel, which was phased out in 2006.
Most of the food consumed by White-backed vultures consists of carrion, or decaying flesh. This makes them vulnerable to poisoning if the carcasses of both wild and domestic animals they feed on are affected.
More than 65% of vultures suffer from lead exposure compared to other raptors and large terrestrial birds.
This is considered above normal, but there is finally an answer to why lead poisoning has been so prevalent among the species.
According to Project Vulture, the population size of White-backed vultures has reduced by 90% over the last three generations. There are less than 7 400 mature birds left.
The study found that vultures ingested lead from ammunition fragments embedded in the carrion.
Considering blood samples were taken from chicks that were still nest-bound, their ingesting lead meant the metal was coming from the food fed to them by their parents.
Lead bullets are the result of game hunting and culling, and disperse into countless fragments throughout the carcass of an animal.
Humans also inadvertently ingest lead fragments when they eat game shot with lead ammunition.
Lead levels ‘concerning’
Head of conservation at BirdLife South Africa, Dr Hanneline Smit-Robinson, said the high levels of lead of a critically endangered bird was “concerning”.
“In related research, which BirdLife South Africa will soon be publishing, it will be shown that chicks fledging from Dronfield suffer from anaemia and liver damage, which may compromise their ability to thrive as free-flying juveniles.”
Lead poisoning compounded with other threats vultures face, such as being poisoned by poachers and flying into power lines, means they face an even more bleak future during their first year of life.
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What can be done?
Van den Heever explained that of the challenges facing vultures, lead poisoining was a preventable scenario.
“This is perfectly preventable. Hunters need to shoot with lead-free ammunition. This is not a criticism of hunting, but we need to be realistic.
“Lead is a toxic substance. We cannot shoot a toxic substance into the environment and forget about it. That bullet will remain in perpetuity and keep poisoning things.”
She explained that the main reason for the current state of lead poisoning was a lack of awareness.
The people Van den Heever has spoken to have told her they never think about the fate of a bullet once it leaves their gun.
“Once they kill an animal, it’s over. Most people just didn’t think of it.”
Making the switch to lead-free ammunition may take some convincing, as there is a price discrepancy between lead and lead-free ammunition.
“Lead bullets are cheaper because they are soft and malleable. But copper bullets need to be carved, which can be more expensive.”
But she is optimistic that the study, the first of its kind in Africa, can make a difference in changing the minds of hunters and farmers.
“We just need the will for people to do the right thing.”
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