Rapid population declines and mortality clusters in three Oriental white-backed vulture Gyps bengalensis colonies in Pakistan due to diclofenac poisoning

Abstract

The population declines affecting Asian Gyps vultures are among the most rapid and geographically widespread recorded for any species. This paper describes the rates and patterns of mortality and population change over 4 years at three Oriental white-backed vulture Gyps bengalensis colonies in Pakistan: Dholewala (initially 421 pairs), Toawala (initially 445 pairs) and Changa Manga (initially 758 pairs). Vulture mortality led to the extirpation of two of these colonies (Changa Manga and Dholewala) in 3 years, and a decline of 54.3% in the third. Visceral gout, indicative of diclofenac poisoning, was the largest single cause of death in vultures examined. Annual adult mortality from diclofenac poisoning was significantly positively correlated with annual population declines at each colony indicating a direct causal relationship. Visceral gout occurred in temporal and spatial clusters suggesting multiple point sources of diclofenac exposure. The spatial and temporal distribution of dead vultures and approximate time since death were used to estimate minimum rates at which colonies encountered carcasses with sufficient diclofenac to cause mortality of 1.26–1.88 carcasses per colony per month. By estimating total carcass consumption at each colony, the percentage of carcasses contaminated with diclofenac was calculated as 1.41–3.02%, exceeding the minimum required to have caused the observed population decline. With populations declining by approximately 50% annually, the long term survival of Gyps vultures in South Asia will require the removal of diclofenac from vulture food and establishment of captive populations for future restoration once the environment is free from contamination.

The conservation of Accipitridae vultures of Nepal: a review

“…Communal roost sites are also regularly used (Gilbert et al 2006). It breeds in colonies in tall trees such as Bombax ceiba and Ficus religiosa, often near human habitation (Paudel 2008;Baral 2010;IUCN 2012c).…”

“…The global population is estimated to be about 45,000 mature individuals (Birdlife International 2012). (Gilbert et al 2006;Prakash et al 2007;Pain et al 2008;Chaudhary et al 2012 Slender-billed Vulture (Fig. 4) Slender-billed Vultures range through southern Nepal.…”

“…Considerable aggregations can form during consumption of carcases (Gilbert et al 2006;Jackson et al 2008). Vultures are exposed to diclofenac when they feed on carcases of livestock that were dosed with the drug shortly before death.…”

Population and breeding success of Red-headed Vulture <i>Sarcogyps calvus</i> and Egyptian Vulture <i>Neophron percnopterus</i> in central west Nepal

“…Studies conducted in Nepal, India and Pakistan show three species of resident Gyps vulture (White-rumped Gyps bengalensis, Long-billed Gyps indicus and Slender-billed Vulture Gyps tenuirostris) have undergone >97% population declines (Baral et al 2004, Prakash et al 2007. Studies conducted in Pakistan showed the complete loss of a large breeding colony of White-rumped Vulture within a short period of 2001 to 2003 (Gilbert et al 2006).…”

Population status, nesting sites and seasonal fluctuation of Egyptian vultures (Neophron percnopterus): Dynamics and implications for the species conservation in and around Jodhpur

“…There has been drastic decline in the vulture population in Indian sub-continent over last two decades (Rahmani, 1998;Prakash, 1999;Prakash and Rahmani, 1999;Virani et al, 2001;Prakash et al, 2003;Chhangani, 2005;Gilbert et al, 2006). Since 1996, the breeding ecology and population of vulture study in and around Jodhpur and in the Thar desert have been examined by monitoring the nesting site, making censuses, recording predation, observing inter-species interaction and locating seasonal migration (Chhangani and Mohnot, 2004;Chhangani, 2002aChhangani, , b, c, 2005Chhangani et al, 2002).…”