Feeding on the carcasses of cattle to which the drug was administered was found to be proving fatal to the survival of these bird species, it was found during a recent survey.
The field survey, conducted by a five-member team from Bombay Natural History Society recently in the Nilgiri Biosphere Reserve and adjacent areas, found that vulture population had been declining at a dangerous pace.
The survey covered Wayanad Wildlife Sanctuary in Kerala, Muthumalai Tiger Reserve and Sathyamangalam Wild Life Sanctuary in Tamil Nadu and Bandipur Tiger Reserve and Rajeev Gandhi National Park, Nagarholai, in Karnataka.
C Sasikumar, ornithologist and chief investigator of the survey, told PTI that the total population of Oriental White-backed Vultures (Gyps bengalensis) in the region could be 100 - 150. A 1992 survey had sighted upto 300 birds of the species in Muthumalai sanctuary alone.
The region was considered a good habitat of the white backed vultures, red headed vultures and Indian long billed vultures (Gyps indicus).
As many as 22 red-headed vultures and one long billed vulture had been recorded during survey in Muthumalai then while the recent survey revealed that population of these species had fallen further.
The number of red-headed vultures could be around 20 and Indian Long-billed vulture was extremely rare in the entire region now, Sasikumar said.
The red headed vultures and white backed vultures were so common in Kerala during 1930s, C K Vishnudas, member of the team said .
"We could not see a single bird of the species in most parts of the state, except in Wayanad Wild Life sanctuary, during a bird survey organised by Kerala Forest and Wild Life department a few months back," he said. It was established in 2004 that Diclofenac (a non-steroidal anti-inflammatory drug), used as painkiller in livestock in the India proved fatal for vultures and the Centre banned the production and use of veterinary Diclofenac in May 2006.
This population of vultures feed mainly on the carcasses of wild ungulates and as long as they remain within the forested area, they are safe from contaminated food.
But the human settlements including tribal villages on the fringes of the forests have a large number domesticated cattle and their carcasses were consumed by vultures at times.
Contiued availability of Diclofenac at drug stores in small towns close to the sanctuaries such as Masinagudi in Tamil Nadu and Gundelpet in Karnataka posed a dire threat to the existing vulture population, Sasikumar said.
Oriental White-backed vultures are capable of moving up to 226 km a day during their foraging. The home-range of the species could be very extensive, in some cases several thousand square kilometers, which would necessitate creation of an area free of dangerous veterinary pain killers to protect the remaining vulture population, he said.
An all-India survey conducted by BNHS in 2007 had found that population of Gyps bengalensis had declined by 99.9 per cent since 1992. Decline of Gyps indicus was 96.8 per cent.
The population of Gyps bengalensis has an average annual rate of decline of 43.9 per cent between 2000-2007, while the combined average annual rate of decline of Gyps indicus was over 16 per cent, he said.
A study by some voluntary conservation groups in the region some time back found that most of the stakeholders, including villagers, cattle owners, veterinarians and drug store owners were unaware of the ban on Diclofenac or its effect on vultures, Sasikumar said.
"This is a very dangerous situation as far as vultures are concerned. If urgent remedial measures are not taken,remaining vulture population here will be extinct soon," he said.
A regular monitoring programme also needed to protect the surviving populations in the area, he said.