AN INVESTIGATION INTO THE DECLINE OF THE BEARDED VULTURE GYPAETUS-BARBATUS IN SOUTHERN AFRICA

In southern Africa the bearded vulture Gypaetus barbatus has lost about 21 000 km2 (38%) of its former breeding range, mainly in the southern (by 1940) and eastern (by 1970) Cape Province. It is now restricted to the mountains of Lesotho and immediately adjacent areas. The present population numbers about 203 pairs. The names 'lammergeier' and 'lammergeyer' were confused with the Afrikaans name 'lammervanger', meaning lamb-catcher, by 6.5% of 1612 farmers returning questionnaires. The English name 'bearded vulture' and the Afrikaans name 'baardaasvoel' should be promoted to prevent the unjustified inference of predation. The amount of food available to bearded vultures in different parts of their range was remarkably similar; in Lesotho it was on average 21 kg/km2/year and during the month of the year when food was most scarce was three times less than this figure. This would support a theoretical population of 14 pairs/1000 km2 (compared to the actual density of 10 pairs/1000 km2), while for the adjacent commercial farmlands the theoretical densities were 10-12 pairs/1000 km2, but actual densities were considerably lower, e.g. 3.5 pairs/1000 km2 in the northeastern Cape. In most of the districts in which bearded vultures have become extinct during this century the food supply would support on average between six and 11 bearded vulture pairs/1000 km2. Food is therefore not considered to be the limiting factor. The main cause of mortality in bearded vultures was poisoning (68% of deaths); this is considered a gross underestimate; 34% of farmers admitted to setting poisons in various baits, mainly against mammalian predators. The average 5000 km2 home range of a pair of bearded vultures on commercial farmlands would include at least 44 farms on which poisons were used. The foraging methods of bearded vultures makes them particularly vulnerable to all forms of poisoned baits, and the eventual extinction of these birds in areas where poisons remain in general use is inevitable.