Occupancy-based monitoring of ungulate prey species in Thailand indicates population stability, but limited recovery

Abstract

Longitudinal studies of wildlife are urgently needed in South-East Asia to understand population responses to the high poaching pressure that characterizes this region. We monitored population trends and habitat use of five heavily poached ungulate species (gaur, sambar, wild pig, red muntjac, and Fea's muntjac) over five years in two protected areas in western Thailand using camera trap surveys. We used single-season occupancy models to investigate effects of ecological and anthropological variables on ungulate distribution, and multi-season models to assess occupancy dynamics over time. Occupancy of gaur and sambar was low (<0.25), but concentrated near saltlicks and at low elevations. Wild pig and muntjac occupancies were 3–4 times higher (0.60–0.80). Wild pig occupancy was lower near villages, but this effect dissipated in the final year of the study, coinciding with a purported decrease in poaching. Wild pig occupancy increased significantly, with the probability of colonizing new sites doubling from 0.40 to 0.81 over time. In contrast, occupancy rates of gaur, sambar, and muntjac did not grow, though they were stable. Poaching pressure during the study was low, perhaps allowing populations to stabilize. But only wild pig (the most resilient of the five species) increased. The failure of gaur and sambar to recover might stem from historical overhunting combined with ecological constraints, particularly low saltlick density. Recovery of ungulates (and the carnivores that depend on them) in overhunted South-East Asian reserves might require intensive interventions, particularly habitat improvement and population augmentation, to achieve conservation objectives.