Improving the conservation of threatened and rare mammal species through translocation to islands: case study Western Australia

Abstract

Systematic study of the islands of Western Australia indicates the occurrence of 254 islands 100 ha or larger in area, with 90% in tropical seas. All but eight and 16 of these islands are free of the exotic carnivores, red fox Vulpes vulpes and cat Felis catus respectively. The few inshore islands to which these predators have spread naturally are instructive in deducing the swimming capability of the fox and cat. When distance from mainland is considered (⩾1 km or ⩾2 km), 147 or 122 islands offer potential as sites for establishing populations of mammal species not otherwise represented on islands and with restricted distribution on mainland Western Australia. A procedure for selecting appropriate islands for translocation is outlined, emphasizing those islands without significant biological characteristics such as large colonies of nesting seabirds and the occurrence of native mammal species, but also considering island area, degree of isolation and habitats present. A prioritized list of candidate species of native terrestrial mammals, based on size of geographical range, natural absence from any Western Australian island, and the degree to which current threatening processes are not being addressed successfully, is provided for more detailed consideration. Because the cat and fox have occurred on the mainland coast of Western Australia for >100 years and ca. 70 years respectively, it is suggested that islands within swimming distance and not yet occupied by these predators are unlikely to be colonized. These islands should therefore be considered as possible translocation sites.