Conservation of Asian Vultures
Vulture populations worldwide are in decline. The most severe cases involve the catastrophic collapse of Gyps populations on the Indian sub-continent. Populations of three species, Oriental white-backed vulture (G. bengalensis), slender-billed vulture (G. tenuirostris), and long-billed vulture (G. indicus), once stable and collectively numbering between 10 and 40 million, have declined by 99% in the last 20 years. The near complete disappearance of these birds is generally considered to be one of the world’s most significant recent ornithological conservation catastrophes. The primary cause of this decline is the use in livestock of the non-steroidal anti-inflammatory drug diclofenac. Although India has recently banned the marketing and manufacture of diclofenac, the drug is still widely used. Furthermore, the impacts of diclofenac in other areas and on migratory wintering birds are not known.
Apart from diclofenac, other human impacts have caused declines of vulture populations throughout Asia. G. tenuirostris, G. bengalensis and Sarcogyps calvus populations in south-east Asia, and G. fulvus and G. himalayensis in central Asia, have all been substantially reduced by changing agricultural practices and reduced food availability. Despite the remnant status of the few remaining south-east Asian birds, they are extremely valuable to conservation because they represent the only populations of these species that are not declining. Likewise, recent simulation modeling and monitoring of the already small central Asian populations suggests population declines that may be best explained by increases in adult mortality rates.
In spite of the conservation crisis facing vultures in Asia and elsewhere, there is almost no information on the true size of vulture populations in any part of their range. This is largely because vultures are among the most difficult of raptors to count. Although they are reasonably faithful to nesting colony sites, individuals breed irregularly, non-breeders are itinerant, and all vultures can travel hundreds of kilometers among feeding sites. At present, the only way to estimate numbers of these birds is by traditional capture and recapture of individuals - a process that requires exceptional effort for relatively poor return, as vultures are notoriously wary and difficult to trap. There is, therefore, an urgent need to develop new techniques to reliably assess the abundance of Asian vultures.
In the last decade, genetic analysis of non-invasively collected samples (hair, scat, feathers) has become a powerful method to "mark" individual wild animals. Recent advances have eliminated many of the obstacles that once biased accurate data interpretation - analysis errors such as allelic dropout and so called “shadowing effects” where multiple individuals are represented by a single putative genotype. These types of errors have been overcome through improvements in both laboratory genetic and statistical mark/recapture techniques.
The vast majority of non-invasive genetic demography studies have focused on mammalian hair and scat. In fact, it is only in the last few years that feathers have been used in this type of analysis. These studies show that multilocus microsatellite genotypes can be effective to estimate survivorship and population densities for large birds of prey. Science-based conservation requires knowledge of the size of threatened populations, yet traditional approaches have never yielded a good estimate of numbers of wild vultures.
The goal of this study is to use non-invasive genetic mark-recapture techniques to estimate demographic characteristics of Asian vulture populations in central and south-east Asia. Over the past two years, my research team has developed, deployed, and refined the field techniques for this study and have established DNA barcoding and genotyping protocols for species and individual identification. Graduate student Yula Kapetanakos has non-invasively collected feather samples from Kazakhstan and Cambodia in a mark-recapture framework to estimate population size and demographic characteristics of these species.