On March 17, 36 vultures died in Sivasagar, Assam after feeding on a poisoned goat carcass intended as bait for feral dogs. The 36 vultures belonged to three different species, namely, the Himalayan griffon (Gyps himalayensis), Oriental white-backed (Gyps bengalensis) and slender-billed (Gyps tenuirostris) vulture, of which the last two are critically endangered. The birds died within half an hour of feeding on the carcass. Seven others were rescued, rehabilitated and released.
This is not a lone incident of vultures dying en masse in India, and poisons are not the only killers of these scavenging raptors. Since December last year, more than 60 vultures have been found dead along the Jaisalmer-Ramdevra railway track in Rajasthan.
Sumit Dookia, a conservationist and ecologist who worked on the Rajasthan case, told The Wire that about 15% of the vultures in Jaisalmer could have died after being hit by trains in the last 6 months. The vulture deaths are linked to the death of other animals near the track, particularly that of cows. Villagers from Dholia and Khetolai in Jaisalmer have tried to remove animal carcasses from near the railway tracks to prevent vultures from getting mowed down by trains, but that has not completely solved the problem, according to Dookia.
This is also not a lone incident of vultures getting mowed down by trains. In another episode that occurred near Jorbeer Vulture Sanctuary in Rajasthan in April 2017, 31 vultures were killed by a train.
Speaking to The Wire, Chris Bowden, the co-chair of the vulture specialist group at the International Union of Conservation of Nature (IUCN), said, “When vultures feed on carcasses in large numbers, many have their heads buried deep in the animal’s flesh, and are unfortunately not well adapted to fast moving trains appearing suddenly”. He added that the trains catch the vultures in a particularly vulnerable moment when they are weighed down with full crop, unable to quickly fly high or away from oncoming trains.
Three decade-long vulture deaths
Environmentalists are fighting tooth and nail to record and formulate plans to prevent vulture deaths, as India has been facing mass mortality of vultures. Three of India’s vulture species have been on the list of critically endangered animals since 2000. Almost 95% of the raptors in India were dead by 2003, and more than 99% were wiped out by 2008. A paper published in Bird Conservation International in December 2017, noted that the population of the three Gyps species of vultures inhabiting India reduced from millions in the 1970s, to a few thousands.
Vibhu Prakash, principal scientist at the Bombay Natural History Society (BNHS), was one of the first to note the decline. Between 1987-1988, he counted 353 nesting pairs of vultures in 29 square-km area of Keoladeo National Park in Bharatpur, Rajasthan, which, by 1998-1999, came down to 20, with no breeding pairs observed in the subsequent years. The decline continued, till vultures were completely wiped out in Bharatpur. Soon, similar reports poured in from across the country of the mass mortality of vultures. Since vultures play critical roles in the ecosystem, their mass mortality has had cascading effects, even on the economy.
Consequences of a vulture population decline
Vultures are extremely efficient scavengers. They can dig deep into dead animals, and 15-20 vultures working together can bring a cattle carcass down to its bone within 20 minutes. With their powerfully corrosive stomach acids, they can safely digest rotting carcass, even those teeming with bacteria that cause deadly diseases like botulism and anthrax. The Madras high court even addressed vultures as ‘sanitary workers’ for their valuable services in disposing off cattle carcasses.
In India, a decline in vulture population by about 10 million between 1992 and 2003, coincided with an increase in dog population from 3.7 million to 7.3 million. Though it is very difficult to find the direct contribution of vulture deaths to the dog population explosion, a large portion of carrion consumed by vultures was made available for dogs during that period.
A study published in 2008 by Anil Markandya, a resource economist at University of Bath, estimated the total cost to the Indian government due to the vulture population decline. He calculated that the population expansion of dogs due to vulture deaths, between 1992 and 2006, resulted in over 38.5 million additional dog bites. From this, Markandya estimated that 47,300 people would have died from rabies, many succumbing to it despite treatment.
The paper further estimated that the mass mortality of vultures during the period may have indirectly cost the Indian government over USD 34 million in treatment costs. It also stated that elimination of vultures could lead to an outburst of rat populations, causing an increased risk of rat-borne epidemic outbreaks like leptospirosis and noted that the neglected carcasses could also act as incubators for microorganisms causing diseases like tuberculosis, anthrax, and foot-and-mouth disease.
There are cultural costs of vulture deaths as well. The Parsi community has a unique funeral ritual where they lay their dead in tall structures called “Towers of Silence” to be consumed by scavenger birds. With the sharp decline in vulture population, this practice could not be sustained.
A decade-long probe into the causes
Worried, environmentalists sought to find the main reason for the vulture deaths. While there were numerous factors that could have been responsible, they narrowed down the list to a few major suspects. The initial suspicion was on poisoned carcass, as reported by Down To Earth in 1999.
Rodenticide was also suspected, as it is commonly used by cattle-lifters to kill cows for their bones and skin. There were also doubt of pesticides indirectly causing the death of vultures, similar to the case of DDT killing off bald eagles in USA in the 1960s. Factors like habitat destruction, poaching or epidemics could also not be ruled out easily.
Then, the collective efforts of the Peregrine Fund and a team of more than a dozen scientists found that the deaths were caused when vultures consumed dead cows treated with the drug Diclofenac – an anti-inflammatory drug intended for humans and used to treat sick cattle. The team found that the cheap and fast-acting pain killer, belonging to the class of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), had disastrous effects on a vulture’s kidneys, causing severe gout and death within 72 hours. Soon, four other NSAIDs were also found to be poisonous to vultures.
“Non-steroidal anti-inflammatory drugs, most notably diclofenac, but now joined by ketoprofen, aceclofenac and nimesulide, used by vets to treat cattle, were [the] hidden and widespread killers of 40 million vultures over the past 20 years in India. They kill slowly, over several days, so the dead vultures are highly dispersed and go unseen.” Bowden told The Wire.
Even after the major cause of death was found, environmentalists had to move a mountain to bring regulations on the use of the drug. After constant battle since the 90s, veterinary use of diclofenac was banned by the Indian government only in 2006. And later in November 2017, the Union Ministry of Health and Family Welfare banned multi-dose vials of the drug. After several NSAIDs were found to kill vultures, Meloxicam, which was proven to be safe for the raptors, has been promoted as an alternative.
Conservation efforts and aftermath of diclofenac ban
Vulture numbers began stabilising slowly after the diclofenac ban, and between 2011 and 2012, there was a slight increase in the population. However, for a successful recovery, environmentalists like Dookia believe that the threat posed by transmission lines, train routes and wind turbines must also be looked into. Bowden believes that any covert use of NSAIDs to treat cattle would prevent the recovery of the raptor’s population.
The main challenge facing vulture conservation is that even today carrion continues to show the presence of diclofenac. BNHS tested the carcasses of lifestocks across the country and found that 6% of the dead animals still showed traces of diclofenac – a number that is still too high for vultures to recover, according to Vibhu Prakash.
Satish Pande, ornithologist and part of the ELA Foundation, noted that farmers spray pesticides on dead animals or bury them to prevent the smell of putrefaction, taking more food off the vultures’ tables. Hence, experts like Prakash believe that safe food should be provided at breeding centres till the vultures are reared to adulthood. The Phansad Wildlife Sanctuary in Maharashtra is one such centre where vultures are fed cattle, sheep or goat carcass, free from any drug contamination, every three to four days.
Since 2004, the Ministry of Environment and Forests has undertaken eight captive breeding programmes. Jatayu Conservation Breeding Centre in Pinjore, Haryana, is one such place housing more than 250 vultures belonging to the three majorly affected species. Likewise, there are breeding centres in Assam, Madhya Pradesh and West Bengal. But even with these centres, very few vultures have been released into the wild since the threat from diclofenac still lurks.
Thus, there is a need to establish certified safe zones to act as release sites for the birds reared in captivity. “Conservation breeding and release programmes have an important role to play in getting birds back into the wild.” said Bowden. He added that it was also important to test the safety levels of the release-areas using monitoring tools, and by planting tracking devices on released vultures.
Vishwam Sankaran is a freelance science writer.