However, they soon noticed that something was amiss - there were three dead vultures among the throng. When they went closer to investigate, they found that the other vultures were all exceptionally lethargic and did not move away - they were sick and apparently dying too.
Fortunately the grapevine works fast, and the BirdLife office in Maun was able to notify Obert Gwapela, Park Manager for Makgadikgadi and Nxai Pan, and he quickly despatched Dr Kebonang Kebonang (DWNP Vet) to the scene.
When the DWNP contingent arrived, many of the sick vultures had recovered and flew off. One of the dead vultures, on examination, was found to have the crop and throat neatly removed, as shown in the photograph below - the rest of the bird was intact.
This is most peculiar: the first reaction on hearing of vultures dying at a waterhole is that they have been poisoned with an organophosphate poison since this makes them very thirsty and they go to water where they die - in order to test for the presence of this poison, the best sample to take is the crop with the poisoned meat in it, but here the crop had been removed? This was looking increasingly like another poisoning incident, and perpetrated by someone who knew how to remove some of the evidence!
This led the investigating team to strongly suspect foul play, and a search was initiated for a poisoned carcase in the area. The presence of about 40 Marabou Storks nearby led to a site where a few small remains of a cow carcase were found; unfortunately spoor and drag marks showed that a Brown Hyaena (another globally threatened animal) had dragged off the bulk of the carcase and it is highly likely that it, too, is now dead from the poison.
Miraculously, by late afternoon, most of the vultures had completely recovered - only three had ingested a fatal dose of the poison and died. This is a real wake-up call to the authorities and to all who are concerned about the poisoning of Botswana's wildlife: this could easily have been a major mortality of all 150 White-backed and 10 Lappet-faced vultures, as well as the 40 Marabou Storks and 15 to 20 Black-backed Jackals that were at the site. And this is the real danger of these poisoning incidents: a few cases involving large numbers of vultures, in the middle of the breeding season, could decimate these already globally threatened birds. Currently, the Makgadikgadi is the most important breeding area for Lappet-faced Vultures in Botswana (and probably in the whole of Africa) and if the 10 birds of this species present at the site had been killed, this would have seriously dented the regional population of these magnificent birds.
BirdLife Botswana would like to thank Super Sande from Jack's Camp for reporting the incident so quickly, and Nicky Bousfield and John Barclay from Uncharted Africa for relaying the information, and sending in photos of the incident. Our special thanks go to our colleagues in DWNP who treated the incident with the importance it deserves and who conducted a swift, professional investigation.
Of course, the investigation is not over; samples from the dead vultures are being analysed at the Veterinary Laboratory, and the perpetrator(s) are being tracked down. We urgently need an arrest and prosecution to send a clear message to wildlife poisoners in Botswana that this practice is not acceptable.