Biological Conservation 109 (2003) 381–390 www.elsevier.com/locate/biocon Catastrophic collapse of Indian white-backed Gyps bengalensis and long-billed Gyps indicus vulture populations V. Prakasha, D.J. Painb,*, A.A. Cunninghamc, P.F. Donaldb, N. Prakasha, A. Vermaa, R. Gargia, S. Sivakumara, A.R. Rahmania aBombay Natural History Society, Hornbill House, Shaheed Bhaagat Singh Road, Mumbai 400 023, India bRSPB, The Lodge, Sandy, Bedfordshire SG19 2DL, UK cInstitute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, UK Received 4 December 2001; received in revised form 26 April 2002; accepted 9 May 2002 Abstract 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 km of road transect surveys carried out in protected areas, the regions around protected areas and linking highways across the country. An additional 5000 kmwere covered in 2000 in previously unsurveyed areas. Further data were collected fromquestionnaires circulated to ornithologists, wildlife experts and forestry officials. Massive declines in the populations of both species were apparent fromall 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 naı¨ ve, e.g. an introduced agent or one fromwhich the species were previously isolated. Immediate steps are needed to confirm this and to identify measures that could be taken to stem the problem. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Griffon; Vultures; Declines; India; Population; Conservation 1. Introduction led vulture (G. indicus). The latter probably comprises two distinct species, Indian vulture G. indicus and slen- Nine or 10 species of vulture occur in India, many of der-billed vulture G. tenuirostris (Rasmussen and Parry, them formerly common. Of these, four or five (depend- 2000) but is treated as one species here as the two forms ing on accepted taxonomy) are griffons, Gyps, a group were not differentiated during fieldwork. of obligate scavengers that typically breed colonially or Prakash (1999) recorded >95% declines in popula- semi-colonially. Gyps vultures specialise in taking the tions of each species between 1988 and 1999 in a soft tissues that make up the bulk of animal carcases national park in northern India, where populations of and therefore comprise the majority of vultures other genera of vultures remained unchanged. Prior to numerically. In most African vulture populations, Gyps the declines in India, populations of Gyps vultures had comprise around 90% of all vulture sightings and in declined or disappeared across huge areas of Peninsular India the figure used to be over 99% (Houston, 1983). Malaysia, Thailand and Indochina where they were However, marked declines have been noted in the formerly common (Thiollay, 1998; Satheesan, 2000; Indian populations of at least two species of Gyps; the BirdLife International, 2001). However, these declines white-backed vulture (G. bengalensis), and the long-bil- appear to have taken place over decades, particularly in the early–mid twentieth century, and were accompanied * Corresponding author. Tel.: +44-1767-680551; fax: +44-1767- by similar declines in other scavenging species such as 683211. adjutant storks (Leptoptilus spp.), black kites (Milvus E-mail address: [email protected] (D.J. Pain). migrans), Brahminy kites (Haliastur indus) and other 0006-3207/03/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0006-3207(02)00164-7 382 V. Prakash et al. / Biological Conservation 109 (2003) 381–390 genera of vultures, such as the red-headed (Sarcogyps in length) were carried out to assess the populations of calvus) (BirdLife International, 2001). Declines in these all raptor species in the north, west and east of India. In countries are believed to have resulted fromimprove- most areas, transects were carried out between March ments in hygiene and concomitant reduction in food and June. In a few areas (Ranthambore, Sariska and availability, persecution by humans and poisoning Keoladeo National Parks and surrounding areas in the (BirdLife International, 2001). north, and Desert and Little Rann National Parks and G. bengalensis breeds in loose colonies or singly in tall surrounding areas in the west) surveys were carried out trees, often near human habitation, whereas G. indicus in December and January. Numbers of birds recorded nests colonially on cliffs (BirdLife International, 2001). are likely to be higher between March and June (post- Both feed at carcases, often in large groups. As recently breeding) than in December and January (e.g. Prakash, as 1985, G. bengalensis was regarded as possibly the 1999). commonest large raptor in the world (Houston, 1985), In the present study, these 6323 kmof transect counts with nest densities being recorded at 12/km2 at Keola- were repeated between April and June 2000, following deo National Park (Prakash, 1989) and nearly 3/km2 in the same routes as previous counts to allow direct com- the city of Delhi (Galushin, 1971), where flocks of sev- parison. One additional 32 kmtransect, for which pre- eral thousand birds were present at carcass dumps. vious data were available, was conducted for G. During the 1970s and 1980s, G. indicus was less com- bengalensis. A further 5041 kmof transects were inclu- mon than G. bengalensis and more patchily distributed ded in our 2000 counts in regions for which there were (Grubh, 1988). Both G. bengalensis and G. indicus were no previous data. The same field staff and researchers found throughout the subcontinent except in southern- were used for approximately two-thirds of the 1991– most areas and Sri Lanka, and neither were considered 1993 and 2000 counts. In 2000, only Gyps vultures were to merit any conservation measures or to face any par- counted along road transects, although Egyptian vul- ticular threats (Grubh, 1983; Grubh et al., 1990). Indeed ture (Neophron percnopterus) and S. calvus were counted numbers of G. bengalensis were considered unnaturally in 13 national parks for which previous (1991–1993) high because of the abundant carcases provided for counts were available. their disposal around human habitation (Ali and In the 1990–1993 counts, both Gyps species were so Grubh, 1980; Grubh et al., 1990). Both species are now common that only groups of five birds or more were classified as ‘‘Critically Endangered’’, placing them counted, whereas in 2000 each individual bird was among the world’s bird species most threatened with counted. The population declines apparent fromdirect global extinction (BirdLife International, 2000, 2001). comparisons of the two data sets are therefore likely to In this paper, we quantify the population declines of be underestimates. Declines are likely to be further Gyps vultures in India, and determine whether there underestimated for areas counted between December have been spatial patterns in the decline. We look for and January during the earlier transects. Road transects evidence of regional effects and assess whether declines followed the methods of Fuller and Mosher (1981). have been lower in protected areas than outside, to try Transects were driven at 10–20 km/h in protected and to identify possible causes of the declines. We also assess surrounding areas, and 50 km/h on highways, and birds the hypothesis that declines have been caused by reduc- recorded sitting or soaring within 500 mof the road. tions in food availability. Road transects are a common method for counting conspicuous raptors (e.g. Hubbard, 1983; Vin˜ uela, 1997). For this study, the North region comprises the 2. Methods States of Haryana, Punjab, Himachal Pradesh, Uttar- anchal, Jammu and Kashmir, Uttar Pradesh and parts 2.1. Population assessments of eastern Rajasthan. The West region comprises the States of Gujarat, most of Rajasthan and west Data for quantifying the decline in vulture popula- Maharashtra. The East region comprises the States of tions were obtained froma numberof sources. West Bengal, and Orissa. The Central region comprises (1) Detailed observations of vultures were made in the States of Madhya Pradesh and the rest of Maharastra. Keoladeo National Park (Bharatpur) in the late 1980s During the road transects, vultures were counted at and the mid-late 1990s. It was these observations that any carcases that were seen. Several carcass dumps were first detected evidence of decline (Prakash, 1999). also revisited to assess vulture populations in these for- (2) We conducted repeat surveys of vultures across mer hotspots. Any flocks of perched vultures found the country. Between 1991 and 1993 nationwide raptor were scanned at 10-min intervals for at least half an surveys were conducted by the Bombay Natural History hour to assess the proportion of birds exhibiting Society, supported by the US Fish and Wildlife Service ‘‘neck-drooping’’ symptoms. During some transects (Samant et al., 1995). In these surveys, 6323 km of road (depending upon the expertise of surveyors), adults were transect surveys (64 transects ranging from8 to 397 km distinguished fromfirst year birds using plumage details. V. Prakash et al. / Biological Conservation 109 (2003) 381–390 383 (3) A third source of data was returns fromover 5000 Table 1 questionnaires sent to ornithologists, other wildlife Number of active nests of Gyps bengalensis at Keoladeo National experts and forestry officials across the country. These Park, northern India (Prakash, 1999, and author’s subsequent data) asked respondents to classify Gyps spp. vulture popula- Year Count tion trends between 1990 and 2000 in their area into one 1985/1986 244 of five classes (‘‘Increase’’, ‘‘No change’’, ‘‘Decline’’, 1987/1988 353 ‘‘Severe decline’’, ‘‘Complete disappearance’’).