Persistence of medium- and large-sized mammals in an oil palm-dominated landscape of Sarawak, Malaysian Borneo

Abstract

Forest mammals in Sarawak are at risk of local extinction from habitat fragmentation. Remnant forests on oil palm estates are important refugia for mammal metapopulations. Metapopulation persistence depends on species’ ability to traverse the oil palm matrix. Using camera traps, we examined the occupancy of medium- to large-mammals in six forest fragments (range=29–990 ha) and the oil palm matrix in northern Sarawak. The forest fragments collectively contained 22 of 24 mammal species occurring in the nearby Lambir Hills National Park, including three megafauna species (Sun bear Helarctos malayanus; Sambar deer Rusa unicolor, Bearded pig Sus barbatus). Species occupancy and richness increased with forest area and declined with distance from forest into oil palm, except for the mesopredators, the Sunda leopard cat (Prionailurus javanensis) and common palm civet (Paradoxurus hermaphroditus), whose occupancy remained constant. Mostly larger species displayed a transient presence up to 1 km into oil palm, including the pig-tailed macaque (Macaca nemestrina), sambar deer (Rusa unicolor), and bearded pig (Sus barbatus). Forest-dependent species, including mouse deer (Tragulus spp.) and banded civet (Hemigalus derbyanus), were rarely observed in oil palm. Source-sink population dynamics appear to determine metapopulation persistence of dietary generalists and mesopredators in oil palm plantations. Retention of forest habitat on oil palm estates improves habitat heterogeneity, enhancing connectivity (forests<1 km apart), securing forest biodiversity and ecological functions that benefit plantations.