Impacts of oil palm agriculture on phyllostomid bat assemblages

Rising global demand for palm oil comes mainly at the expense of tropical forests, and palm plantations are increasing steadily in Latin America. Conversion of forest to oil palm agriculture accelerates biodiversity loss by dramatically altering availability and abundance of resources. Assessing the impact of these monocultures on highly diverse keystone groups such as bats is of particular ecological and economic importance. We compared phyllostomid bat assemblages in mature lowland forest interior, at forest margins and within oil palm plantations in southwestern Costa Rica. A total of 45 mist-netting nights in the late dry season yielded 1235 individual captures from 31 species. Bat assemblages in oil palm plantations were clearly distinct from those at forest sites and exhibited lower species richness, similar to results reported for Southeast Asia. Assemblage structure within oil palm plantations was characterized by increased relative abundance of common frugivorous Stenodermatinae and the loss of rare species, mainly disturbance-sensitive animalivorous Phyllostominae. Although plantations may serve as flyways for highly mobile matrix-tolerant species, even small oil palm plantations seem to act as effective barriers for many others, particularly understory gleaning animalivores. By decreasing landscape permeability even for highly mobile animals such as bats, oil palm agriculture may consequently reduce population connectivity and foster faunal impoverishment, which in turn can diminish crucial ecosystem services provided by bats. The advancing expansion of these monocultures in Latin America calls for appropriate precautionary conservation measures to protect and preserve biodiversity in oil palm growing countries.