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Nine species of vulture can be found living in India, but most are now in danger of extinction after a rapid and major population collapse in recent decades. As recently as the 1980s there were up to 80 million white-rumped vultures (Gyps bengalensis) in India; but today the population numbers only several thousand.
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The cause of the rapid plunge in the population was initially unclear, but in 2003 was traced to the anti-inflammatory drug diclofenac, which is lethal to vultures when they consume the carcasses of dead animals treated with it.
Vultures previously played an important role in public sanitation in India and their disappearance has resulted in a number of problems.
History
Vultures in India live in communities and are generally very dependent on human activities. The Hindu religion, which represents 80% of the country's population, is particularly favorable to vultures. Some Hindus do not eat cows, which they consider sacred, and when a cow dies, it is left to be fed on by vultures. Of the estimated 500 million cattle in India, only 4% were destined for consumption by humans as meat. Vultures constituted the natural animal disposal system, processing carcasses and nearly 15,000 vultures have been observed at the carcass depositories in capital New Delhi.
Decline
In the 1990s, a decrease in the number of vultures was noted by Vibhu Prakash of the Bombay Natural History Society, who had monitored vulture populations at Keoladeo National Park. As the decline accelerated, the international scientific community looked for a reason. There were many difficulties to be overcome because vultures could not legally be killed for scientific study in India and freshly dead animals had become extremely rare, a situation exacerbated by the extremely hot weather in India where temperatures before the monsoon routinely exceed 40 °C (104 °F). Andrew Cunningham of the Zoological Society of London found that the usual suspects of pesticide poisoning, industrial pollutants or bacteria did not show anything abnormal in the vultures he could examine and suspected a new type of toxin exposure.
Causes
After work on possible viral causes of the decline, the culprit was discovered by Dr. Lindsay Oaks and his team in 2003 to be diclofenac. Diclofenac is a common anti-inflammatory drug administered to livestock and is used to treat the symptoms of inflammation, fevers and/or pain associated with disease or wounds. It was widely used in India beginning in the 1990s. The drug is fatal to vultures, however, and a vulture is exposed to a mortal dose of diclofenac if it eats from the carcass of an animal that has been treated with diclofenac recently. A simulation model demonstrated that if only 1% of carcasses were contaminated by diclofenac, Indian vultures would be decimated, and a study of carcasses showed that about 10% were contaminated.
Gyps species were the most affected by diclofenac. The population of the White-rumped vulture (Gyps bengalensis) fell 99.7% between 1993 and 2002. The populations of the Indian vulture (Gyps indicus) and the slender-billed vulture (Gyps tenuirostris) fell 97.4%. The percentages differ slightly because the white-rumped vulture is more sensitive to diclofenac than the other two species, but all three were in danger of extinction. Two other species of Gyps, the Himalayan vulture (Gyps himalayensis) and the Eurasian griffon (Gyps fulvus) were less affected, the Eurasian griffon because it only winters in India and has a much smaller initial population and the Himalayan vulture, with a similarly small population, because it is exclusively mountain-dwelling. Vulture populations have continued to decline in India at a rate of between 20% and 40% each year since 2007.
Consequences
The sudden collapse of the natural animal disposal system in India has had multiple consequences. The carcasses formerly eaten by vultures rot in village fields leading to contaminated drinking water. The disappearance of vultures has allowed other species such as rat and wild dog populations to grow. These newly abundant scavengers are not as efficient as vultures. A vulture’s metabolism is a true “dead-end” for pathogens, but dogs and rats become carriers of the pathogens. India has an estimated 18 million wild dogs, the largest population of carnivores in the world, which has led to increase in leopards invading inhabited areas preying on feral dogs leading to conflicts with humans.
The mammals also carry diseases from rotting carcasses such as rabies, anthrax, plague etc. and are indirectly responsible for thousands of human deaths. In India, 30,000 people die from rabies each year, more than half the world's total. Around half a million Indians are treated for rabies each year, at a cost of ₹1,500 (US$22) per person, while the average wage in India is ₹120 (US$1.80) per day. According to a study in 2007, the expenses for medical care to treat animal bites cost India ₹750 million (US$11 million) per year. In addition to the cost of care, the government faces the problem of managing the population of disease carriers. Vaccination and sterilization of animals cost money. It is estimated that the decline of vultures costs India ₹1,700 billion (US$25 billion) per year.
According to Parsi beliefs, Earth, Fire, and Water are sacred elements, and both cremation and burial are sacrilegious. For the deceased Parsi to reach heaven, vultures serve as intermediaries between earth and sky. The dead body is placed on a Tower of Silence where vultures, by consuming the body, liberate the soul. Due to the decline in vulture population, Parsis have been obliged to drop these ancient customs for reasons of hygiene, since now bodies take six months to disappear.
Reaction
Following the findings on diclofenac, the drug was banned for veterinary use in India on March 11, 2006; Nepal followed suit in August, 2006, and Pakistan shortly thereafter. A replacement drug was quickly developed and proposed after tests on vultures in captivity: meloxicam. Meloxicam affects cattle the same way as diclofenac, but is harmless for vultures. Diclofenac for human use was still being diverted into veterinary uses through black markets in certain parts of India as of 2009.
Despite the vulture crisis, diclofenac remains available in other countries including many in Europe. It was controversially approved for veterinary use in Spain in 2013 and continues to be available, despite Spain being home to around 90% of the European vulture population and an independent simulation showing that the drug could reduce the population of vultures by 1-8% annually. Spain's medicine agency presented simulations suggesting that the number of deaths would be quite small.