Painkillers like diclofenac, even in minute concentration, can kill vultures. Credit: Kaushal Patel
Vultures remain at great risk of fatal poisoning from livestock carcasses, even in areas of India where they are protected, because of continued use of diclofenac, a painkiller used to treat cattle.
In a diet DNA metabarcoding study1, a very high proportion of vulture faecal samples from various parts of the country revealed DNA from cows and water buffalo. The genetic material of these domestic livestock showed up even in samples collected from inside and near protected areas, where the birds forage.
The multi-institutional study led by the Bengaluru-based National Centre for Biological Sciences-Tata Institute of Fundamental Research (NCBS-TIFR) contradicts a previous theory that vultures inside protected areas mostly feed on carcasses of wild animals, and are safe from poisoning by drugs, such as diclofenac, used to treat livestock. Diclofenac was banned from veterinary practice in South Asia after Gyps vultures consuming cattle remains died in millions during the 1990s and early 2000s. “It is crucial to keep removing harmful veterinary drugs from the environment to safeguard the remaining vulture populations,” says ecologist, Mousumi Ghosh-Harihar, at NCBS-TIFR, in Bengaluru.
The study authors say India’s dense concentration of livestock, the presence of feral cattle within protected areas, and the extensive foraging range of vultures — they often fly long distances into neighbouring countries to find food — might explain the results. Vultures recycle and break down dead biomass, mitigating the spread of infectious diseases.
The scientists collected 642 vulture dropping samples from nesting and roosting sites inside and outside protected areas in Karnataka, Tamil Nadu, Kerala, Madhya Pradesh, Rajasthan and Himachal Pradesh between 2018 and 2022. They extracted DNA, amplified the sequences of interest and used a next generation sequencing approach on them.
Molecular data from 419 samples helped identify the vulture species. As many as 30 unique DNA sequences indicated the scavengers preyed on 28 animal species. “We pinpointed vulture species, sex and the species they fed on,” Ghosh-Harihar says.
Even tiny amounts of painkillers or non-steroidal anti-inflammatory drugs (NSAIDs) cause kidney failure in the scavengers, says raptor biologist and co-author Vibhu Prakash. “A single, poisoned dead animal can kill several vultures at once because they feed in large groups,” Prakash says.
Of the 14 NSAIDs used in India, four — nimesulide, diclofenac, ketoprofen and aceclofenac — are harmful to the birds. The latter three are outlawed for veterinary use in India but continue to be manufactured for human medical use. “Many who treat cattle in India are not trained in veterinary medicine and they tend to misuse these drugs,” Prakash says.
Spain and Italy approved the use of the drug in 2013. Spain reported its first diclofenac-linked vulture death in 2021 prompting conservationists to call for a ban. In India, researchers suggest systematic and periodic testing of dead cattle. “We can’t solely rely on protected areas to conserve vultures,” Prakash adds.
