Nine species of vulture can be found living in India, but most are now endangered after a rapid and major population collapse exceeding 99.5% in recent decades. In the early 1980s, three species of Gyps vultures (the white-rumped vulture, the long-billed vulture and the slender-billed vulture) had a combined estimated population of 40 million in South Asia, while in 2017 the total population numbered only 19,000 (6,000, 12,000, and 1,000 respectively). A major contributing factor in declining populations of vultures is believed to be the widespread use of drugs such as diclofenac, a nonsteroidal anti-inflammatory drug (NSAID) once commonly given to livestock. The drug is believed to have been passed onto the vultures through the flesh of dead cattle who were given diclofenac in their last days of life, which then causes kidney failure in vultures. Data modelling revealed that a tiny proportion (about 0.8%) of livestock carcasses containing diclofenac can cause significant crashes in vulture populations. Without vultures, a large number of animal carcasses were left to rot, posing a serious risk to human health by providing a potential breeding ground for infectious germs and proliferation of pests such as rats. The loss of vultures also resulted in a substantial increase in the population of feral dogs, whose bites are the most common cause of human rabies. The feral dog population in India increased by at least 5 million, resulting in over 38 million additional dog bites and more than 47,000 extra deaths from rabies, costing $34 billion in economic impact. Veterinary usage of diclofenac has been banned in India since 2006. Meloxicam, another NSAID, which is rapidly metabolized and harmless to vultures, has been suggested as an acceptable substitute for diclofenac. In addition, various conservation schemes are in place to help recover the vulture population. The population is recovering slowly and the decline has been significantly arrested in India, Pakistan and Nepal following a strict ban on the drugs causing harm to the vultures.
History Vultures in India live in communities and are generally very dependent on human activities. Hinduism, which represents about 79.8% of the country's population according to the 2011 Census, is particularly favorable to vultures. Cows are considered sacred by the majority of Hindus, so cow meat is generally not consumed by many Hindus due to religious beliefs. This results in cow carcasses being 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. Due to their Zoroastrian beliefs, India's Parsis relied mainly on vultures to eat corpses left in Towers of Silence. Vultures constituted the natural animal disposal system, processing carcasses, and nearly 15,000 vultures have been observed at the carcass depositories in the Indian capital of 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. Parsis in Mumbai started to notice in the early 1990s that there were fewer birds at the Towers of Silence in Mumbai. Villagers in northern India started to notice the declining vulture population in the mid-1990s. As the decline accelerated, the international scientific community attempted to investigate the cause of such decline. However, it was not easy to examine this issue 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). In 2002, National Geographic reported that scientists were "not sure" of the reason for the 95% population decline. 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 In 2003, after research on the possible viral causes of the decline, the culprit was discovered by Lindsay Oaks and his team at The Peregrine Fund 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 on eating from the carcass of an animal that had been treated with diclofenac recently. A simulation model demonstrated that if only 1% of carcasses were contaminated by diclofenac, Indian vulture populations would fall by between 60% and 90% annually, while a study of carcasses showed that about 10% were contaminated. A genus of vultures called Gyps was 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 are in danger of extinction. Two other species of Gyps, the Himalayan vulture (Gyps himalayensis) and the Eurasian griffon (Gyps fulvus), have been 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.
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