Frequently Asked Questions (FAQs)


Q. Is diclofenac the only cause of the decline in vultures across Asia?

A. Yes, diclofenac is the main, if not the only, cause of the crash in vulture numbers across South Asia. A large number of peer-reviewed scientific publications have conclusively established that diclofenac is the principal cause of the declines. These include studies on the cause of death of vultures in the wild, experiments demonstrating that diclofenac in livestock carcasses is toxic to vultures, measurements of the prevalence of diclofenac (>10%) in livestock carcasses available to vultures, and detailed modelling that has determined that the measured prevalence and concentrations of diclofenac in carcasses are sufficient to account on their own for the observed decline in vulture numbers. This does not mean that other causes of mortality are unimportant. With the now tiny and still declining population of vultures present in Asia any additional cause of mortality are making the situation worse. However, the principal cause of the declines remains the presence of diclofenac and only the complete removal of diclofenac from the environment will allow vulture number to begin to recover.


Q. Why are some species apparently not affected by diclofenac?

A. Differences between species in the toxicity of non-steroidal anti-inflammatory drugs (NSAIDs) is characteristic of NSAIDs. The most striking example is the differing toxicity of paracetamol within mammals. For humans and many other mammals paracatemol is a safe and reliable pain killer, yet doses that we would take for a mild headache are highly toxic to domestic cats and other cat species. Similarly, while diclofenac is highly toxic to vultures from the genus Gyps , New World vultures (that are more closely related to storks) and crows can tolerate very high doses of diclofenac without mortality. It is likely that physiological differences in kidney function between species are responsible for the observed variable toxicity.


Q. Can breeding centres really work to bring about the recovery of vultures in Asia?

A. Vulture conservation breeding centres were an essential tool for the survival of the Californian condor and the for the successful reintroduction of bearded vultures and Eurasian griffon vultures across Europe. The California Condor was down to just 24 birds in the wild, before these individuals were captured. Over the next decade captive breeding and release has increased this population, and in 2009 over 200 birds are now present in the wild having been successfully released following captive breeding. In conservation the capture and captive breeding of species is usually a last resort. Asia’s vultures are no exception, with in 2007 numbers of white-backed vultures having declined by more than 99.9% over the last 12 years and with no indication that decline rates (48% a year) have slowed. Because of the scale and speed of these declines capturing and breeding vultures in Asia is essential to ensure populations persist. Without breeding centres it is very likely that by the time diclofenac is completely removed from the environment that no vultures will be left to stage a recovery.


Q. Is it realistic and desirable for vultures to return to their former abundance as this was artificially high?
A. It has been suggested by some that the decline of vultures in the Indian subcontinent is acceptable because it represents a fall from abnormally high numbers supported by the huge and unnatural food supply proved by hundreds of millions of domesticated ungulates. It is certainly likely that the amount of food for vultures in the late 20th century was at an all-time high, and higher even than it was when wild ungulates abounded before the advent of pastoralism and agriculture. However, the vulture population in the subcontinent has now declined so drastically that it is now probably much lower than it has been at any time since the end of the last ice age. Even in protected areas where wild ungulates and their natural predators are present in large numbers, vultures are virtually absent. Kaziranga National Park is a stark example. Hence, although the high population of vultures before the decline was supported by human activity, the vulture population is now much lower than could be considered a "natural" level in the absence of humans. If toxic drugs are removed from domesticated ungulates, vulture populations are expected to recover slowly because they only rear a maximum of one chick per year. In addition, there may be less food for them now because carcass disposal practices have changed while they were rare. However, the upper limit on their future population density should be much higher than at present, especially in and near protected areas where carcasses of wild ungulates are available.




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