Koalas on Australian Islands

Despite substantial conservation investment, populations of the endemic and iconic koala (Phascolarctos cinereus) continue to decline across much of their native Australian range, resulting in their Endangered conservation status. Island refugia can offer a critical strategy for conservation but may also act as ecological traps, contributing to further declines. Nevertheless, systematic efforts to record koala occurrences on Australian islands are currently lacking. This has left key gaps in our knowledge about the status, origin, and distribution of island koala populations, the factors influencing their persistence, and the extent of threats island koalas face. This study addresses these gaps by creating the first comprehensive database of koalas on Australian islands, characterising their distribution, status, and origin. We then integrated the new database with spatial mapping to assess the geographic extent of anthropogenic and environmental stressors on islands with extant koala populations. We applied path analysis to model the effects of abiotic, biotic, and anthropogenic factors on island koala persistence. We found records of koalas (historical and/or current) on 37 Australian islands spanning subtropical to temperate climates, with at least 15 islands currently supporting koala populations. The key threats with consistent spatial patterns to extant island koala populations include habitat destruction and overbrowsing, being more pronounced at lower latitudes. Path analysis revealed that translocation effort is a key driver of koala persistence on islands. These findings highlight islands needing urgent conservation action as current and potential long-term koala refuges, providing a foundation for targeted, spatially informed management and translocation strategies to support this iconic species.