Marko Ascher

Marco Ascher

Factors facilitating the successful introduction of species of the mammalian order Carnivora on islands

A major cause of ecosystem perturbation and biodiversity losses on islands is the introduction of alien species and more than any other vertebrate group introduced mammals have reportedly caused problems. In this study we focus on introduced terrestrial mammalian carnivores and the factors, which are crucial for colonizing islands. Therefore we collected data on the Carnivora fauna of 178 marine islands covering the southern and northern hemisphere, all ecoregions and climatic zones. Carnivora introduced on islands have lower mean female body weight and smaller mean litter size compared to native Carnivora species. We could show that island size has no effect on the occurrence and the number of species of non-native Carnivora. Our results indicate that the occurrence of native carnivores and human population density have a significant impact on the establishment of introduced carnivores on islands. The number of introduced species on islands decreased significantly with increasing number of native carnivores and was positively related to human population density. Our results confirm that one of the main reasons for the occurrence of non-native Carnivora on islands was and still is the presence of humans. As the human population is growing and therefore more native species will have to face the negative human impact on island ecosystems, the future seems to be not very bright. On the other hand, as conservationists and scientists are nowadays more connected to each other than ever in history, also the likelihood to find more effective control measures against introduced species will be higher.