Impact of Posttyphoon Hunting on Mariana Fruit Bats (Pteropus mariannus)

We examined the abundance of Mariana fruit bats (Pteropus mariannus Desmarest) on the Pacific islands of Rota and Guam before and after a severe typhoon in December 2002. After the typhoon, bat abundance declined by 70% on Rota. On Guam, bat abundance initially increased by ca. 100 individuals (103%), perhaps due to immigration from Rota, but then declined an average of 32% from pretyphoon levels for the remainder of 2003. An increase in posttyphoon hunting pressure represents at least a partial cause for the decline observed on Rota. Interviews with 29 suspected poachers on the island revealed a 34% increase in bat harvest from 2002 to 2003. Hunting of bats is rare on Guam because access to their remaining habitat is restricted by the U.S. military. However, juvenile bats are preyed on by introduced brown tree snakes (Boiga irregularis Bechstein) on Guam to such an extent that little to no withinisland recruitment occurs. We therefore suggest that the brief increase and subsequent decrease in bat abundance on Guam was due to interisland movements, a reduction in the source population (Rota), and/or changes in roosting patterns on Guam. Rota is vital to recovery prospects for P. mariannus in the southern Mariana Islands because it holds the only viable population in this part of the archipelago. If the species is not conserved, forest ecosystems may suffer because P. mariannus is almost certainly an important seed disperser and pollinator on these depauparate islands. We recommend that agencies responsible for managing hunted fruit bat populations make special efforts to prevent illegal hunting after severe typhoons.