This study examines how different scientific regimes have contributed differently to the way two Western Australian islands are managed. Rottnest Island and Garden Island are located off the coast of Perth, the capital of Western Australia. This paper contrasts the way science was conducted on Rottnest from the 1950s to 1970s, and this is contrasted with the way it was done on Garden Island in the 1970s and 1980s. On Rottnest, zoology and medicine were detached from the island management, yet impacted upon the island landscape. On Garden Island, ecology and geography were integrated with, and served, management. Differences in the social and political context of the times, and between the philosophical approaches and cultures of the scientists, are shown to have created different rôles for scientists in the management of the islands, and illustrate the on-going dialectic between two scientific cultures, one a culture of biomedical abstraction on Rottnest, and the other a culture of pragmatic holism on Garden Island.