The historical extirpation of the bearded vulture gypaetus barbatus in the western alps (france - italy): Modelling the impact of human persecution

Abstract

Human persecution may have been the major cause of extirpation of the bearded vulture Gypaetus barbatus in the western Alps around 1920–1930. However, as shown in a previous work (Mingozzi & Estève, 1996), historical information by itself is insufficient to uphold this hypothesis because the real extent of the shooting pressure endured by the species is not ascertainable. The aim of this paper was to test whether the rapid population decline (30–40 years) shown by historical data is consistent with human persecution. By making assumptions about hypothetical population size and natural survival rates, we tried to assess what rate of additional adult mortality caused by human impact would eventually have led to extirpation. The size of our hypothetical population was estimated by comparison between the current population size (number of breeding pairs) of the golden eagle Aquila chrysaetos in the Pyrenees and in the western Alps. All the life-history parameters available in the recent European literature were used as reference data for a Population Vulnerability Analysis (PVA). A series of computer simulations was performed with R.C. Lacy's programme, VORTEX. Three different scenarios were explored: one without hunting persecution and two with different killing rates. The results suggest that the vulnerability of G. barbatus was extremely high and even a moderate rate of killing would have led to extirpation within a very few decades, as suggested by the historical data. Moreover, the species vulnerability shown by the simulations has led to cautious conclusions about the success rate of the current reintroduction project of the bearded vulture in the Alps. © 1996 Taylor & Francis Group, LLC.