The Oriental white-backed vulture (OWBV; Gyps bengalensis) was once one of the most common raptors in the Indian subcontinent1. A population decline of >95%, starting in the 1990s, was first noted at Keoladeo National Park, India2. Since then, catastrophic declines, also involving Gyps indicus and Gyps tenuirostris, have continued to be reported across the subcontinent3. Consequently these vultures are now listed as critically endangered by BirdLife International4. In 2000, the Peregrine Fund initiated its Asian Vulture Crisis Project with the Ornithological Society of Pakistan, establishing study sites at 16 OWBV colonies in the Kasur, Khanewal and Muzaffargarh–Layyah Districts of Pakistan to measure mortality at over 2,400 active nest sites5. Between 2000 and 2003, high annual adult and subadult mortality (5–86%) and resulting population declines (34–95%) (ref. 5 and M.G., manuscript in preparation) were associated with renal failure and visceral gout. Here, we provide results that directly correlate residues of the anti-inflammatory drug diclofenac with renal failure. Diclofenac residues and renal disease were reproduced experimentally in OWBVs by direct oral exposure and through feeding vultures diclofenac-treated livestock. We propose that residues of veterinary diclofenac are responsible for the OWBV decline.
The authors thank S. Pritchard, S. Donahoe and M. Asim for technical assistance, and T. Taruscio and HEJ Laboratories (Karachi) for performing diclofenac assays. We thank V. Beasley, K. Beckman, P. Benson, T. Besser, T. Cade, K. Mealey, R. Poppenga, P. Talcott, The Ornithological Society of Pakistan, Punjab Department of Wildlife and Parks, the National Council for the Conservation of Wildlife (Islamabad), World Wildlife Fund (Pakistan), and Brigadier M. Ahmed for their cooperation. This research was conducted as part of The Peregrine Fund's Asian Vulture Crisis Project and was supported by the Gordon and Betty Moore Foundation, The Peregrine Fund, Disney Wildlife Conservation Fund, San Diego Zoological Society, and the United Nations, Ivorybill and Summit Foundations.Authors' contributions J.L.O. coordinated the overall diagnostic work and performed microbiology; M.G., M.Z.V. and A.A.K. coordinated field biology and collected samples; R.T.W. supervised field biology; C.U.M., B.A.R. and H.L.S. performed pathology; and S.A., M.J.I.C., M.A. and A.A. collected biology data and samples.