Animal drug blamed for vanishing vultures

Posted: 29 January 2004

Author: John Rowley

For several years scientists have been monitoring the dramatic decline of vultures in India. Now new research has linked the unexplained vulture deaths to the use of a drug used to treat livestock in South Asia, and conservation organisations are calling for it to be banned.

A study, published in the latest issue of the journal Nature, links the veterinary use of "diclofenac" with the catastrophic crash of three vulture species.

The vulture is now critically endangered. Photo RSPB
The vulture is now critically endangered. Photo RSPB
The vulture is now critically endangered© rspb-images.com

The discovery is the result of a three-year effort by an international team of scientists, assembled and led by US-based Peregrine Fund. It includes members from Washington State University, The Ornithological Society of Pakistan (OSP), Bird Conservation Nepal, United States Geological Service, Zoological Society of San Diego, and University of California, Davis.

The Fund and several other conservation organisations, including the UK-based Royal Society for the Protection of Birds (RSPB), are now calling for the drug to be banned for use in livestock.

Race against time

"To lose three of the world's species of raptors would be a tragedy beyond comprehension," says Dr. Tom Cade, Founder of The Peregrine Fund. "The speed of the decline is eerily similar to the decline of the Peregrine Falcon in the 1960s. We're in another race against time to save these species." In the last decade, population losses of more than 95 per cent of three vulture species have been reported in many areas - a decline without precedent among vertebrate species. The three species are the Oriental White-backed Vulture, Long-billed Vulture, and Slender-billed Vulture in South Asia. "This discovery is significant in that it is the first known case of a pharmaceutical causing major ecological damage over a huge geographic area and threatening three species with extinction," said Dr. Lindsay Oaks of Washington State University, lead investigator for The Peregrine Fund's team.

"Finding that a drug is responsible for the collapse and threatened extinction of these species is helpful yet alarming," said Dr. Rick Watson, International Programmes Director for The Peregrine Fund. "Helpful, because now we can do something about it and we may have time to save these species. Alarming, because this may not be the only pharmaceutical impacting wildlife."

Widespread toxic effect

Diclofenac is a non-steroidal anti-inflammatory drug that has been in human use for pain and inflammation for decades. The veterinary use of diclofenac on livestock in South Asia has grown in the past decade and is now widespread. Livestock that die shortly after being treated with diclofenac contain sufficient residues to cause kidney failure and death in vultures that consume livestock carcasses.

Like Peregrine Falcons and DDT, vultures in this case are the "canary in the coal miner's cage", say the researchers. They say that vultures are sampling the environment and their deaths and population collapse have demonstrated a widespread toxic effect. The results are important to toxicologists, conservationists, and drug manufacturers worldwide. "Vultures have an important ecological role in the Asian environment, where they have been relied upon for millennia to clean up and remove dead livestock and even human corpses. Their loss has important economic, cultural, and human health consequences," says Dr. Munir Virani, Biologist for The Peregrine Fund. Virani coordinated the field investigations across Nepal, India, and Pakistan.

"Declines of this magnitude in once very common species have not been seen since the extinction of the Great Auk, or the Passenger Pigeon in the 19th century," said Dr. Martin Gilbert, veterinarian for The Peregrine Fund.

The Fund and its partners, as well as senior government officials from affected countries, will take part in an international Summit Meeting in in Kathmandu, Nepal, next month. This will aim to develop a strategic response to this new environmental threat.

Millions of deaths

The decline in vulture numbers was first observed by the Bombay Natural History Society in the Keoladeo National Park at Bharatpur, south of Delhi. Surveys since then show that the number of white-backed vultures - which used to be India's most common species - have plummeted by more than 99 per cent, with the loss of tens of millions of birds, says Dr Debbie Payne of the Royal Society for the Proection of Bords (RSPB).

Reports of declines in the species came from all over India. Carcasses all over the country which would normally be devoured by some 20,000 birds apiece are being left to rot rather than being picked clean.

"The decline of Asian vultures is one of the steepest declines experienced by any bird species, and is certainly faster than that suffered by the dodo before its extinction. If nothing is done these vulture species will become extinct," says Dr Payne.

Commenting on the new research findings, Dr Rhys Green of the RSPB said: "only a small proportion of dead livestock need to contain lethal doses of diclofenac to cause these alarming vulture population declines."

Dr Andrew Cunningham, of the London Zoological Society's Institute of Zoology, said: "Vultures are keystone species and their declines are having adverse effects upon other wildlife, domestic animals and people. The vultures' population crash has led to an increase in the number of feral dogs which poses a range of disease threats."

A conservation priority

In 2000, the white-rumped vulture (Gyps bengalensis), and the closely related slender-billed and Indian vultures (Gyps tenuirostris and Gyps indicus), were classified as Critically Endangered. This status recognises that these species are now more vulnerable to global extinction than the tiger and the great Indian rhinoceros, which are both classified as Endangered.

Currently, the use of diclofenac to treat livestock appears to be largely restricted to countries in southern Asia, including India, Pakistan and Nepal. However, there are concerns that, were this drug to be used in a similar way in Africa, the Middle East or Europe, it might affect closely related species in these regions too.

To protect vultures across the world, the RSPB, the Institute of Zoology (London), the Bombay Natural History Society, OSP, Bird Conservation Nepal (BirdLife in Nepal), BirdLife International, and The Peregrine Fund are calling on governments of countries with vulture populations, and manufacturers of diclofenac, to ban the use of this drug in livestock. It is believed the recovery of vulture populations in southern Asia will not be effective until their exposure to diclofenac has been removed.

Dr Mark Avery, the RSPB's director of conservation, said: "The Asian vulture crisis is one of the world's most important conservation priorities. The RSPB is committing significant resources to a programme to ensure that these birds have a future."

Related Links:

Royal Society for the Protection of Birds

Vulture Declines

Bombay Natural History Society

The Peregrine Fund