Oil palm cultivation critically affects sociality in a threatened Malaysian primate

Anna Holzner,Krishna N Balasubramaniam,Nadine Ruppert,Brigitte M Weiß,Anja Widdig

doi:10.1038/s41598-021-89783-3

Abstract

Human-induced habitat alterations globally threaten animal populations, often evoking complex behavioural responses in wildlife. This may be particularly dramatic when negatively affecting social behaviour, which fundamentally determines individual fitness and offspring survival in group-living animals. Here, we provide first evidence for significant behavioural modifications in sociality of southern pig-tailed macaques visiting Malaysian oil palm plantations in search of food despite elevated predation risk. Specifically, we found critical reductions of key positive social interactions but higher rates of aggression in the plantation interior compared to the plantation edge (i.e. plantation areas bordering the forest) and the forest. At the plantation edge, affiliation even increased compared to the forest, while central positions in the macaques' social network structure shifted from high-ranking adult females and immatures to low-ranking individuals. Further, plantations also affected mother–infant relationships, with macaque mothers being more protective in the open plantation environment. We suggest that although primates can temporarily persist in human-altered habitats, their ability to permanently adapt requires the presence of close-by forest and comes with a trade-off in sociality, potentially hampering individual fitness and infant survival. Studies like ours remain critical for understanding species’ adaptability to anthropogenic landscapes, which may ultimately contribute to facilitating their coexistence with humans and preserving biodiversity.

Highlights

The ongoing expansion of anthropogenic landscapes threatens rainforest ecosystems and the survival of many species[1]
We studied two habituated groups of macaques inhabiting the Segari Melintang Forest Reserve in Peninsular Malaysia and the surrounding oil palm plantation, with daily plantation visits lasting on average 2.9 hours
Behavioural data were collected in the forest, at the plantation edge and in the plantation interior

Summary

Introduction

The ongoing expansion of anthropogenic landscapes threatens rainforest ecosystems and the survival of many species[1]. Plasticity in social behaviour may be critical in determining how well a species can cope in human-altered landscapes, as sociality plays a fundamental role in group-living animals[12]. Disruptions of the mother–infant relationship caused by habitat alterations may have severe consequences for offspring health and survival Despite their growing significance, quantitative studies on anthropogenic impact on wildlife behaviour often lack comparative assessments across time and space (reviewed in Ref.[33]). Differences in primate sociality between natural and anthropogenic habitats have not been systematically assessed This is crucial to understand in order to assess species’ adaptability to human-modified landscapes and, to develop effective conservation strategies that will ensure the long-term survival of primates and other species

Methods

Results

Conclusion