A ban on a veterinary drug that has caused devastating vulture die-offs in South Asia is beginning to produce benefits, a new survey concludes. But vulture populations in India and neighboring nations will continue to decline without greater efforts to banish the compound from the birds’ food supply.
Since the 1990s, the region’s once robust vulture populations have plummeted by up to 99.9%. Today, research estimate just 11,000 oriental white-backed vultures (Gypos bengalensis) remain, for instance, down from tens of millions. Long-billed vultures (G. inidcus) are now thought to number about 45,000 and slender-billed vultures (G. tenuirostris) just 1,000.
The culprit, studies showed, was an anti-inflammatory drug called diclofenac that farmers commonly gave to cattle and buffalo to ease pain and swelling. The birds die of kidney failure after eating the carcasses.
India, Nepal and Pakistan banned veterinary use of diclofenac in 2006. Now, in PLoS ONE, researchers report that fewer carcasses are contaminated with the drug, and that even contaminated animals have lower concentrations. Overall, at the time of the ban, about 11% of carcasses in India were contaminated. That proportion has now fallen to about 6.5%, and concentration of the drug in contaminated animals has also fallen.
The bad news, however, is that the numbers suggest substantial illegal use of the drug continues – and that the gains won’t stop vulture deaths. For instance, the researchers estimate that populations of the most susceptible species –the white-back vulture — will continue to decline at 18% per year.
So far, the only safe alternative to diclofenaic used in India is a drug called meloxicam, but vets are still prescribing other drugs that threaten the birds. “There is still a job to do to make sure that safe alternative drugs are used,” says the study’s lead author, Richard Cuthbert of the Royal Society for the Protection of Birds in the United Kingdom. “Unfortunately some of the alternatives have not been tested for their safety to vultures and one drug in increasing use, ketoprofen, is already known to be toxic to vultures.”
Even as conservationists work to end the drug threat, they are also thinking about vulture restoration. There are now five captive breeding centers for vultures in India, Pakistan and Nepal, and five Indian zoos are developing new facilities. – David Malakoff | May 11, 2011
Source: Cuthbert R, Taggart MA, Prakash V, Saini M, Swarup D, et al. (2011) Effectiveness of Action in India to Reduce Exposure of Gyps Vultures to the Toxic Veterinary Drug Diclofenac. PLoS ONE. doi:10.1371/journal.pone.0019069
Image Courtesy Royal Society for the Protection of Birds, UK