Lost Population of Indian Vultures
Pratha Sah and Felix Francis
India has nine species of vultures in the wild including the Oriental White-backed Vulture (Gyps bengalensis), Long-Billed Vulture (Gyps indicus), Slender-Billed Vulture (Gyps tenuirostris), Egyptian Vulture (Neophron percnopterus), Red-Headed Vulture (Sarcogyps calvus), Indian Griffon Vulture (Gyps fulvus), Himalayan Griffon (Gyps himalayensis), Cinereous Vulture (Aegypius monachus), and Bearded Vulture (Gypaetus barbatus). Among them, the white-backed, long-billed, and slender-billed vultures are recognized by the International Union for the Conservation of Nature (IUCN), the World Conservation Union, as critically endangered.
Decline of vulture populations in India was first recorded at the Keoladeo Ghana National Park, Rajasthan during mid 1980’s to mid 1990’s, followed by Northern India road counts. Declines have been projected in excess of 97% over a 12 year period in India.
The ‘Neck drooping’ phenomenon though reported in Eurasian vultures, had never been observed in India before the period of decline. ‘Neck drooping’ was first observed in Keoladeo National Park, where birds would exhibit this behavior for prolonged periods over several weeks before collapsing and falling out of trees, just prior to death.
In India, the initial hypotheses for the drastic decline in population were non-availability of food (dead livestock) as they were perhaps being removed for commercial purposes, or an unknown viral epidemic disease. Visceral gout, an accumulation of uric acid within tissues and on the surfaces of internal organs, was observed in 85% of dead vultures found. Death was caused due to renal failure, which is known to occur as a result of metabolic, infectious or toxic disease.
Histopathology revealed that there was severe renal tubule damage in all the cases, which became acute in 1-4 days, and minimal inflammation, indicating a toxic cause. However toxicological studies did not point to heavy metal poisoning.
Another hypothesis was the introduction of a new risk factor in the environment, to which the birds were exposed. A possible candidate was the veterinary analgesic drug Diclofenac, which was introduced for veterinary use in the late 1980s in the subcontinent. Like ibuprofen and aspirin, diclofenac can be used to treat ailments such as a sore leg. The unintended consequence comes when livestock die shortly after being treated with the drug. Their bodies contain sufficient residues to cause visceral gout in the vultures.
Experiments showed that captive vultures were highly susceptible to Diclofenac, and were killed by kidney failure within a short time of feeding on the carcass of an animal treated with the normal veterinary dose. Routinely used veterinary drugs as well as those new in the market were surveyed extensively to identify those that could damage kidneys and only Diclofenac stood out. Residue analysis in kidney samples showed a perfect correlation between gout and Diclofenac residues. Furthermore, vultures fed with either Diclofenac or treated buffalo carcasses, died of gout. They had the exact identical pathology and tissue residues as the wild cases.
There have been several problems due to the decline of vulture population in India. In addition to putting some of the vulture species close to extinction, increase in putrefying carcasses have amplified disease risks for wildlife, livestock and humans. In some areas the population of feral dogs, being the main scavenging species in the absence of vultures, has been observed to have increased.
Government banned diclofenac in 2006. However, diclofenac was an important drug for veterinarians and farmers in Asia, where livestock need to be treated for symptoms of pain, fever and inflammation. Before banning diclofenac, it was crucial to find a safe alternative to it. After intensive research, meloxicam was declared to be a safe alternative to diclofenac. The only initial hitch to this was that meloxicam was more expensive mainly because of its limited production. Prior to the ban on diclofenac, meloxicam was manufactured by only a single pharmaceutical company in India. In 2008, a minimum of 15 companies were making meloxicam and now the drug is widely available for sale in pharmaceutical shops in India and Nepal.
The Bombay Natural Historical Society (BNHS) propagated the concept of captive breeding as a viable option to save the creatures. Several states including Assam, West Bengal, Rajasthan, Madhya Pradesh, Uttar Pradesh, Uttarakhand, Himachal Pradesh, and Maharahtra reported on their natural breeding population of vultures. The Union environment ministry decided to establish four additional rescue and breeding centers in Hyderabad (Andhra Pradesh), Bhopal (Madhya Pradesh), Bhubaneshwar (Orissa), and Junagarh (Gujarat) under the supervision of the Central Zoo Authority of India. But restoration of native population by captive breeding will be a long process as the vultures are slow breeders. They give birth to only one chick a year and a baby takes nearly four years to attain sexual maturity, for the population to be restored to its original size within our lifetime.
It is obvious that if the vultures are to stay, an immediate and multidirectional strategy must be adopted. Enhanced awareness must be there among scientists and policy makers about the fact of decline, the role of Diclofenac, and to discuss possible steps to address the problem. Testing of alternative veterinary drugs must be supported. Finally, strengthening education and awareness campaigns and beginning the conservation efforts right form the grassroots should help restore the population of these nature cleaners. The ultimate levels in the food chain ought to be there for the chain to be functional.
