Marked Decline in Bearded Pig (Sus barbatus) Detections in Sabah, Malaysia, during the African Swine Fever Outbreak, 2021.

Abstract

African swine fever (ASF) has recently swept through Southeast Asia, beginning in 2018, posing a significant threat to populations of native wild pig species. In Borneo, the population of wild bearded pigs (Sus barbatus) declined sharply during the period of regional ASF spread. This paper presents results of WWF-Malaysia surveys of bearded pigs in the Malaysian state of Sabah, in the northern part of Borneo, that showed changes over a 6-yr period (2019-25), starting before the 2021 ASF outbreak. Surveys were conducted along 2-km transects at 28 sites across 10 forest reserves and parks by using a combination of camera trapping and direct observations. The findings revealed high bearded pig occurrence in 2019-20, with a mean of 12.67 pigs per 100 camera-trap nights, followed by a precipitous decline from March 2021 to December 2022 and a slight increase in detections from 2023 onward. These results documented a marked decline of at least one order of magnitude in bearded pig detections across Sabah that coincided with the period of regional ASF spread, and they showed continued low populations even 5 yr after the epidemic was initially recorded. The survey findings provide an important ecologic baseline for monitoring bearded pig populations and highlight the need for integrated wildlife-disease surveillance in the region.