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Decline in vulture populations in some parts of the world, including India, may have serious consequences for ecosystems and humans alike, according to a new study that suggests poisoning is the greatest extinction risk facing the scavengers.
Poisoning is the greatest extinction risk facing vultures, and impacts 88 per cent of threatened vulture species, researchers from University of Utah in the U.S. have said.
They are unfortunate victims
In many continents, vultures are the unfortunate victims of poisoned carcasses — especially impactful because dozens, or even hundreds — of vultures can feast on a single carcass, they said.
Populations of most vulture species around the world are now either declining or on the brink of extinction.
Other scavengers will enter human habitat
Losses of vultures can allow other scavengers to flourish. Proliferation of such scavengers could bring bacteria and viruses from carcasses into human cities, researchers said.
They examined factors affecting the extinction risk of more than 100 bird species, including 22 species of vultures, which eat carrion exclusively, and other scavenging birds that have broader diets.
Their make could be their unmaking
The results suggest several inherent ecological traits that likely contribute to vultures’ extinction risk, including their large body masses, slow reproductive rates and highly specialised diets, researchers said.
In the mid-1990s India experienced a precipitous vulture decline, with more than 95 per cent of vultures disappearing by the early 2000s, they said.
“That was a massive collapse that led a lot of people to really focus more attention on vultures,” said Evan Buechley from the University of Utah.
This drug called diclofenac
The cause was eventually traced to diclofenac, a veterinary anti-inflammatory drug that relieved pain in cattle, but proved highly toxic to vultures, researchers said.
Hundreds of vultures would flock to each cattle carcass.
And if the cattle had recently been treated with diclofenac, hundreds of vultures would die, they said.
Because of this highly gregarious feeding behaviour, less than one per cent of cattle carcasses contaminated with diclofenac could account for the steep vulture decline.
Spurt in feral dogs and the rabies link
Following the decline of vultures, India experienced a strong uptick in feral dogs — by an estimated seven million, researchers said.
The increase in dogs, potentially feeding on disease-ridden carcasses, is thought to have at least partially caused the rabies outbreak that was estimated to have killed 48,000 people from 1992-2006 in India — deaths that may have been avoided if not for the disappearance of vultures, researchers said.
It is happening in sub-Saharan Africa
Now, the centre of the vulture crisis is in sub-Saharan Africa, they said.
“In Africa, it is a lot more challenging. It is a darker story,” said Buechley.
The findings were published in the journal Biological Conservation.