Minimal Spillover of Native Small Mammals From Bornean Tropical Forests Into Adjacent Oil Palm Plantations

Abstract

In the face of rapid tropical agricultural expansion, preservation of tropical forest remnants is crucially important. Forest remnants often about the edges of new or established plantations, so landscape-level conservation requires an understanding of the balance between ecosystem services and disservices provided by forest, including potential crop yield reductions caused by species such as rodents, an important pest group in oil palm plantations. However, very little is known about the scale of any spillover of native species which inhabit forest into adjacent agricultural areas. We examined the distribution and behaviour of small mammals across an edge separating logged tropical forest and oil palm plantations in Sabah, Malaysian Borneo, using a dual approach. We used a trapping grid to reveal patterns of species relative abundance across the forest-plantation edge, and tracked individuals of forest species using a spool-and-line. We uncovered little evidence that the native forest small mammal community crosses the edge and uses the plantation, although two invasive small mammal species were found across the whole edge gradient. Of 10 forest species detected, we found only the adaptable murid Maxomys whiteheadi in the plantation, where it persisted at low abundances across all sampling points, including in the plantation interior control site. This pattern is more consistent with persistence of M. whiteheadi throughout plantations than with spill-over from forest fragments. On the forest side, observed species richness of small mammals increased with distance into the interior, suggesting a negative edge effect may exist within forest remnants. Of 23 successfully tracked small mammals, only one M. whiteheadi crossed the forest-plantation edge, and overall, this species was significantly repelled from crossing into plantation habitat. Our results suggest that spillover of native small mammals contributes little to oil palm damage close to forestplantation edges, but that oil palm negatively impacts small mammal populations within adjacent forest remnants.

The impacts of tropical agriculture on biodiversity: A meta‐analysis

“…Our study supports the existing literature highlighting the adverse impacts of tropical agriculture upon animal assemblages (Chapman et al, 2019; Gibson et al, 2011; Ocampo‐Ariza et al, 2019; Ramamonjisoa et al, 2020). Adding to this, our meta‐analysis is the first to compare the magnitude and direction of the impacts of different food crops across the whole of the tropics, and demonstrates that agricultural conversion across a range of ecosystems has an effect on biodiversity, depending on the type of crop and intensity of land use.…”

Land‐use change and biodiversity: Challenges for assembling evidence on the greatest threat to nature

“…Linking these measurements to functional traits may help us determine what characterizes winners and losers. Examining species behavior can also provide insights into subtle land‐use change effects (Chapman et al, 2019; Davison et al, 2019). Still, investigating these detailed variables is difficult, resource demanding, and subject to unique local variation.…”

“…Linking these measurements to functional traits may help us determine what characterizes winners and losers. Examining species behavior can also provide insights into subtle land-use change effects (Chapman et al, 2019;Davison et al, 2019).…”

Edge effects on trophic cascades in tropical rainforests

“…Edge effects have an impact not only on small mammal community composition, but also on foraging behavior and patterns of movement (Chapman et al. 2019). Vertebrate assemblages in disturbed forest margins exert weak predation pressure and play a lesser role in the top‐down control of invertebrate populations.…”