Alien Mammals in the Afrotropical Region and Their Impact on the Vertebrate Biodiversity: A Review

Introduction: of alien species may pose enormous threat to indigenous flora and fauna. Among introduced animals probably the most destructive to the natural environment are mammals. This is true at least in regard to the Afrotropical Region (sub-Saharan Africa). The presented paper attempt to summarize our knowledge on alien mammals in this region and their impact on the indigenous vertebrate fauna. This review includes 56 mammal species belonging to 20 families introduced to sub-Saharan Africa in the last 2000 years. Most are representatives of the following orders: Artiodactyla Carnivora and Primates. Most species introduced to sub-Saharan Africa originated from the Oriental (n = 20) and Palearctic Region (n = 19). Two species, Mus musculus and Rattus rattus, have been introduced before 1400 (probably as early as 800 AD); three other were introduced between 1401 and 1700. The first half of the 17th century saw the highest number (n = 10) of introduced species. While during the years 1651 and 1850, only two species were introduced, in the following 175 years (1851-2025) as many as 24 species were introduced. Ten of the introduced mammal species, namely Sus scrofa, Capra hircus, Rattus rattus, R. norvegicus, Mus musculus, Felis catus, Canis familiaris, Viverricula indica, Urva auropunctata and Maccaca fuscicularis become invasive species. A total of 39 mammal species were relocated (mainly for hunting purpose) within sub-Saharan Africa. Most of them were representatives of the family Bovidae (76.9%). Relocations are not considered as introductions. Based on published records of impacts of alien mammals on the vertebrate fauna of the sub-Saharan Africa, the following mechanisms may be distinguished: predation, competition, hybridization, transmission of diseases and parasites; habitat destruction (grazing / herbivory / browsing). Most vertebrate species (79.4%) were affected through direct predation or predation and habitat destruction (7.1%) or predation and competition (1.4%). Alien mammals has caused habitat destruction for only 10 species (7.1%). Other effects (competition and genetic pollution) were marginal (3.5%). At least 144 vertebrate species represented by 52 families were affected by alien mammals in sub-Saharan Africa, 3 amphibian, 23 reptiles, 89 birds and 29 mammals. As result of mammal introduction, 65 species in sub-Saharan Africa became globally extinct, 45 are threatened (in RDB) and 31 other species are in decline, although not included in RDB. Most extinct birds were affected by introduced rats, mouse feral cats and dogs. In continental Africa, only seven vertebrate species are negatively affected by alien mammals. All the others affected vertebrates occur on islands. Especially high rate of extinction was recorded in the Mascarenes. In comparison with alien birds in sub-Saharan Africa, the number introduced mammals species is much lower, but their negative effect on vertebrate fauna much higher.