In the Cook Islands the population of Pteropus tonganus tonganus is thought to be declining, but a lack of knowledge of its status, feeding and roosting requirements has precluded effective conservation plans. We surveyed P. t. tonganus on the Cook Islands through observations, counts and interviews with local residents. We estimated the population to be c. 1,730 on Rarotonga and 78 on Mangaia. A lack of suitable habitat on Mangaia was the most important factor affecting abundance. Overhunting appears to have reduced the populations on both islands. All roost sites were found in undisturbed forest on steep slopes and ridges in the inner and most inaccessible parts of the islands, with roost preference determined by the relative safety from humans rather than food availability. The residents of the Cook Islands seem generally unaware of the serious threat the bats face, with little thought for sustainable hunting. For successful conservation it will be important to alter people's negative perception of these mammals, promoting the value of the bats both ecologically and as a potential source of income from tourists. Habitat protection and enhancement, particularly on Mangaia, will be essential.