Two US researchers have found the cause of the unprecedented decline in the population of vultures in India and neighbouring Pakistan.
Lindsay Oaks and Richard Watson, from The Peregrine Fund in the US, have revealed that a veterinary drug residue in cattle and livestock carcasses is killing most of the South Asian vultures, leaving them on the brink of extinction.
They discovered the vultures were being poisoned by residues of an anti-inflammatory drug (diclofenac) used in cattle and other livestock, whose carcasses they feed on.
“The story is far from over and the stakes are high. The failure to effectively control carcass contamination by diclofenac will likely lead to extinction of these magnificent birds which, through their scavenger role, have controlled the spread of infectious disease for millennia, as well as provided other important ecological services,” the researchers said.
Oaks and Watson described their scientific investigations, including their many challenges and setbacks, following the unprecedented decline in the population of two of the world’s most abundant raptors – the Oriental White-backed vulture and the Long-billed vulture – in India in the 1990s, and neighbouring Pakistan by the early 2000s.
They describe how they were able to prove that the commonly used anti-inflammatory drug diclofenac, fed to ailing cattle and other livestock, was being ingested by the wild birds feeding on the carcasses and causing visceral gout, a manifestation of renal failure.
In spite of the researchers’ 10-year crusade and significant accomplishments, veterinary diclofenac continues to be used widely and illegally almost four years after the drug was banned, leaving the fate of wild Gyps vultures in doubt.
The authors highlight a number of potential measures, which could lead to a more effective implementation of the ban.
Their work has been presented in a chapter of the new book, Wildlife Ecotoxicology – Forensic Approaches, published by Springer.