Historic and recent status of the Kosrae flying fox (Pteropus ualanus) (Chiroptera: Pteropidae) on Kosrae, Micronesia

Abstract

Seven species of flying foxes of the genus Pteropus have been described from the Caroline Islands and Mariana Islands of Micronesia. Among the five extant species, P. ualanus of Kosrae is the least studied. We review the history of research on P. ualanus and summarize data from recent surveys. Early historical accounts suggest that P. ualanus was abundant until a severe population bottleneck, attributed to an infectious disease, allegedly reduced the population to two individuals during 1926–1927. During 1982 and 1983, we found three colonies and a minimum of 600–700 bats in the mountains. Subsequently two new colonies became established in coastal localities by 1994 and 2002 and currently represent the largest colonies. During 2013 and 2014, Hayes visited four confirmed and two possible colonies (three in the mountains, three along the coast) ranging in size from two to 1038 individuals and counted a minimum of 1765 individuals. Long-term changes occurred in the size of colonies. Because not all individuals were counted and at least one other colony likely exists, the population probably exceeds 2000 and may exceed 3000 individuals. The population may not have reached its carrying capacity and may still be increasing. Potential existential threats include infectious disease, typhoons, overhunting, and habitat loss.