Catastrophic collapse of Indian white-backed Gyps bengalensis and long-billed Gyps indicus vulture populations

摘要

In 2000, we conducted a survey to quantify the declines in the populations of Gyps bengalensis and G. indicus across India since 1990-1993. Directly comparable data for the two periods were obtained from over 6000 kin of road transect surveys carried out in protected areas, the regions around protected areas and linking highways across the country. An additional 5000 km were covered in 2000 in previously unsurveyed areas. Further data were collected from questionnaires circulated to ornithologists, wildlife experts and forestry officials. Massive declines in the populations of both species were apparent from all parts of the country, and exceeded 92% overall. The extent of declines did not differ between protected areas and elsewhere. Apparently sick birds, with drooping necks, were observed in all regions, and dead adult and juvenile vultures were frequently observed. Food availability did not decline greatly over this period. The patterns of declines and the presence of sick and dead birds indicate epidemic disease as a possible cause. If so, this is likely to be an agent to which the population is naive, e.g. an introduced agent or one, from which the species were previously isolated. Immediate steps are needed to confirm this and to identify measures that could be taken to stem the problem.