Bearded pig (Sus barbatus) utilisation of a fragmented forest–oil palm landscape in Sabah, Malaysian Borneo

Abstract

Context Oil palm plantations have become a dominant landscape in Southeast Asia, yet we still understand relatively little about the ways wildlife are adapting to fragmented mosaics of forest and oil palm. The bearded pig is of great ecological, social and conservation importance in Borneo and is declining in many parts of its range due to deforestation, habitat fragmentation and overhunting. Aims We assessed how the bearded pig is adapting to oil palm expansion by investigating habitat utilisation, activity patterns, body condition and minimum group size in a mosaic landscape composed of forest fragments and surrounding oil palm plantations. Methods We conducted our study in Sabah, Malaysian Borneo, in and around the Lower Kinabatangan Wildlife Sanctuary, a protected area consisting of secondary forest fragments (ranging 1200–7400ha) situated within an extensive oil palm matrix. We modelled bearded pig habitat use in forest fragments and oil palm plantations using survey data from line transects. Camera traps placed throughout the forest fragments were used to assess pig activity patterns, body condition and minimum group size. Key results All forest transects and 80% of plantation transects showed pig presence, but mean pig signs per transect were much more prevalent in forest (70.00±13.00s.e.) than in plantations (0.91±0.42s.e.). Pig tracks had a positive relationship with leaf cover and a negative relationship with grass cover; pig rooting sites had a positive relationship with wet and moderate soils compared with drier soils. Ninety-five percent of pigs displayed ‘good’ or ‘very good’ body condition in forests across the study area. Pigs also aggregated in small groups (mean=2.7±0.1s.e. individuals), and showed largely diurnal activity patterns with peak activity taking place at dawn and dusk. Groups with piglets and juveniles were more active during the day and less active at night as compared to overall activity patterns for all groups. Conclusions Our findings suggest that bearded pigs in our study area regularly utilise oil palm as habitat, as indicated by their signs in most oil palm sites surveyed. However, secondary forest fragments are used much more frequently and for a wider range of behaviours (e.g. nesting, wallowing) than adjacent oil palm plantations. These forests clearly remain the most important habitat for the bearded pig in the Lower Kinabatangan Wildlife Sanctuary, and their protection is a high conservation priority for this species. Implications Consistent bearded pig presence in oil palm is potentially an indication of successful adaptation to agricultural expansion in the study area. The apparently good body condition displayed by the vast majority of pigs in our study likely results from year-round cross-border fruit subsidies from surrounding oil palm plantations. The consistent diurnal activity displayed by groups containing piglets and juveniles may indicate predator avoidance strategies, whereas the substantial nocturnal activity we observed by other groups could suggest fewer threats for larger individuals. However, the overall effects of oil palm expansion in the region on bearded pig population health, foraging ecology, and movement ecology remain unknown.A