Quantifying changes in sun bear distribution and their forest habitat in Sumatra

High rates of deforestation are presumed to adversely affect large-bodied mammal populations across South-east Asia. Understanding how these species respond to deforestation is therefore important for their conservation, particularly for more cryptic species that have proved a challenge to enumerate. Here, we use an occupancy approach based on detection/non-detection data collected over two survey periods to conduct the first assessment of spatio-temporal changes in sun bear distribution. We measured sun bear population trends through repeat camera-trap surveys and assessed their response to varying levels of deforestation in four study areas located in and around the 13300km2 Kerinci Seblat National Park (KSNP), Sumatra, from 2004/06 to 2009/11. The crude results suggested a decline in sun bear distribution, from 0.683 [0.5190.810; 95% confidence intervals (CIs)] to 0.444 (0.2530.584), but there were considerable overlaps in temporal CIs. This overall change in occupancy was partially driven by the significant decline (9.4%year1) in one subpopulation living in the study area that underwent the highest rate of deforestation (0.96%year1). Meanwhile, sun bear subpopulations living in areas experiencing lower deforestation rates (i.e. <0.60%year1) appear to be less affected by forest clearance. Our study demonstrates that occupancy modelling is a useful and replicable tool for monitoring sun bear populations in KSNP and elsewhere. Our results confirm that KSNP is a stronghold for sun bears, while also forewarning of the detrimental effects of ongoing illegal deforestation on sun bear distributions.