Many Asian Vultures Close to Extinction, Survey Finds
for National Geographic News
|May 1, 2008|
Several species of Asian vulture will be extinct within a decade, new research warns.
The carrion-eating birds have been on the decline due to exposure to a common livestock drug.
Now a survey of vultures in northern and central India has found the birds' populations have plunged to near-extinction levels—one species is down 99.9 percent since surveys began in the 1990s.
"These species are in trouble," said Todd Katzner, director of conservation and field research at the National Aviary in Pittsburgh, Pennsylvania. "Ten years? It may be sooner."
The study appeared this week in the Journal of the Bombay Natural History Society.
Asian vultures first began to die mysteriously in the 1990s. Eventually experts suspected veterinary diclofenac, a popular and inexpensive anti-inflammatory drug given to livestock in India.
A 2004 study confirmed vultures that ate carcasses of diclofenac-treated cows were dying, most likely from kidney failure. Although the drug was banned in India in 2006, poor enforcement has meant that leftover stocks of the drug still find their way into cattle.
Even a single exposure can be lethal for the birds. "It gets them once and that's it," Katzner said.
Researchers from the Bombay Natural History Society and the Zoological Society of London counted live vultures along roadways in northern and central India between March 2007 and June 2007, covering more than 11,700 miles (18,900 kilometers).
Their data lay out what could be the final chapter for several vulture species.
Oriental white-backed vultures have declined catastrophically: There may now be as few as 11,000 animals, compared to tens of millions just two decades ago.
Long-billed and slender-billed vultures have each fallen by almost 97 percent: 45,000 and 1,000 individuals, respectively, remain in India.
The disappearances may have a direct impact on public health and even social customs.
A 2001 article in the British Medical Journal linked two outbreaks of anthrax in humans to an absence of vultures, which safely scavenge anthrax-infected cattle in a country where facilities for incineration and efficient carcass processing are rare.
In addition the absence of vultures has also been a blow to India's small Parsi ethnic minority.
Parsis, who are prohibited by their religion from burying, burning, or submerging their dead, lay bodies in physical structures, called "Towers of Silence," to be consumed by vultures and other carrion-eating birds.
Without vultures, Parsis have been forced to turn to other alternatives, such as giant solar reflectors, to hasten decomposition.
Banned but Cheap
Efforts to eradicate the use of diclofenac in cattle have faltered due to poor enforcement and the widespread use of the human version of the drug in livestock.
"The main challenge is the huge stocks still available with distributors because of [its] long shelf life," said Vibhu Prakash, the study's lead author.
While manufacturing the drug is illegal, state-level regulators "have not said anything about the existing stocks," Prakash said.
"The drug inspectors have to make sure that the drug manufactured after August 2006 should not be sold on the market."
"It is a tall order to enforce this in our country."
Even worse, human diclofenac—which is comparable to the painkiller ibuprofen—is less expensive than the banned veterinary version of the drug.
"This gets filtered into the veterinary sector a lot," Prakash said. "So, [until] human diclofenac use is banned, its continued use in livestock is a distinct possibility."
Authorities have also introduced a substitute drug for livestock called meloxicam.
But meloxicam costs three to five times more than diclofenac, said Anil Kumar Chhangani, a research scientist at Jai Narain Vyas University in Jodhpur.
While more than 20 drugmakers have flooded the market with diclofenac for years, "there are just a few companies making meloxicam," Chhangani said.
Conservationists' last hope is to gather as many vultures as possible into captive breeding programs for a decade or more.
This would give time for the Indian government to completely eradicate diclofenac from the market.
A 2004 conservation plan calls for the creation of six breeding centers in South Asia, each producing 25 pairs from each of the three critically endangered species.
According to the plan, a center would be able to release a hundred pairs of vultures in about 15 years. Three centers are up and running in India, and a fourth center was established in Pakistan in 2006.
"We still have a long way to go," study author Prakash said.
Of course, there are other factors behind the vultures' demise, including the loss of habitat and nesting grounds to urbanization.
So diclofenac "may be a major cause," research scientist Chhangani said, "but it is not the cause of the decline."
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