2021/10/18 by Rigas Tsiakiris, John M. Halley, Kalliopi Stara +5 · 1 citation
Environmental Science · Agricultural and Biological Sciences · #Animal Ecology and Behavior Studies #Ecology and Vegetation Dynamics Studies #Plant and animal studies #Vulture #Allee effect #Threatened species #Population #Population size #Biology #Geography #Ecology #Fishery #Zoology #Demography #Habitat
paper · pdf · doi:10.5194/we-21-79-2021
openalex publication_date 2021/10/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Abstract. Vultures are among the most threatened avian taxa in the world. When vultures aggregate in large numbers to feed, poisoned carcasses can extirpate entire populations at once. In the light of shrinking numbers worldwide, restocking and reintroduction projects, where wild or captive-bred vultures are released back into nature, constitute a crucial management tool, successfully implemented in many countries. However, reestablishment of sustainable vulture populations to their historical ranges remains a serious challenge, especially if the threat of poisoning persists, which is usually the case. In this study, we model the outcome of a restocking project where an initial colony is subject to repeated poisoning events. We use as an example the isolated population of the griffon vulture (Gyps fulvus) in Cyprus. Mathematical considerations and model simulations show that the probability of colony persistence depends on the initial population size and the intensity and frequency of the poisoning incidents. This type of scenario creates an Allee effect that requires a colony to exceed a minimum size in order to survive. Also in this scenario, a sequence of small but frequent poisoning episodes is worse on average than a few large and rare ones of the same cumulative mortality. Future population reinforcement efforts for vultures should focus on the release of adult birds in adequate numbers for the successful establishment of sustainable colonies and should involve a reduction in small but persistent sources of mortality such as the poison baiting of small canids that until now has been neglected by conservation scientists.