Vulture restaurant slowed deaths, but extinction looms
Providing regular and reliable supplies of uncontaminated carcases is a well-established tool in vulture conservation. Among their many applications, vulture restaurants are used to provide a safe food source in areas where carcasses are commonly baited with poisons.
But even where a vulture restaurant is operating, there is no way of preventing the birds feeding elsewhere on contaminated carcases. Where the use of a toxic substance in treating livestock is pervasive, the best that can be hoped is to slow down the rate at which the local vulture population approaches extinction, while efforts are made to take the toxic substance out of the environment. Without a change in practice by veterinarians and livestock owners, extinction may be postponed, but is still inevitable.
Sadly, extinction now seems inevitable for the vulture colony described in the study described below, which was carried out between November 2003 and June 2004.
A team from the Peregrine Fund set out to find whether vulture restaurants could be used in the Indian subcontinent to reduce exposure to the veterinary anti-inflammatory drug diclofenac. Recent catastrophic declines in three Gyps species, Slender-billed Gyps tenuirostris, Indian G. indicus and White-rumped (Oriental White-backed) Vulture Gyps bengalensis have been attributed to the toxic effects of the drug upon birds which have fed on treated livestock. Affected vultures die of visceral gout.
Their findings are described in the current issue of Bird Conservation International (Vulture restaurants and their role in reducing diclofenac exposure in Asian vultures, MARTIN GILBERT, RICHARD T. WATSON, SHAKEEL AHMED, MUHAMMAD ASIM and JEFF A. JOHNSON, Bird Conservation International (2007) 17:1–16.).
The restaurant was established at the White-rumped Vulture colony at Toawala, in Punjab province, Pakistan. The vultures were offered the carcases of donkeys, purchased locally and held for a week to ensure that any diclofenac residues had been eliminated.
Mean daily mortality in the colony when carcases were provided was 0.072 birds per day (8 birds in 111 days), compared with 0.387 birds per day (41 birds in 106 days) during non-provisioning control periods.
The researchers collected 50 dead adult and sub-adult vultures during the study period. Visceral gout, indicative of renal failure possibly due to diclofenac poisoning, was found in 29 of the 30 dead vultures that were available for necropsy.
At least five vultures were found dead with visceral gout while the restaurant was operating. “Even under optimum conditions it is not possible to eliminate diclofenac exposure entirely where alternative carcass sources are readily available,” the authors assert.
The authors conclude that restaurants can reduce, but not eliminate, diclofenac exposure. “Supplementary feeding may prove to be a useful management tool for slowing declines locally in the short term,” until diclofenac can be withdrawn from veterinary use.
Education of veterinarians and livestock owners to avoid treatment of terminally ill livestock, or to bury or burn carcasses of recently treated livestock, may also be helpful. Otherwise, “extinction is inevitable in all populations foraging in areas where diclofenac is in veterinary use and treated carcasses become vulture food at sufficient frequency to cause deaths and negative population growth.”
Bird Conservation International is the official journal of BirdLife International. It provides stimulating, up-to-date coverage of bird conservation topics important in today's world. For more information: BirdLife: Bird Conservation International