Insights into the abundance and ecology of Asian tapirs using camera-trap bycatch data

Asian tapirs (Tapirus indicus) are among Southeast Asia’s most iconic yet understudied large mammals. Despite their
endangered status and ecological importance, current knowledge remains limited, particularly in the northern parts of
their range. We used camera-trap bycatch data from southern Thailand’s Khlong Saeng – Khao Sok Forest Complex to
estimate population abundance and density using a multinomial model with an uncertain strip width buffer for non-spatial
capture-recapture data. From 91 detections, we identified a minimum of 43 individuals and estimated an abundance of 62.4
individuals (95% CrI: 49–85). This abundance corresponds to densities of 6.1 individuals/100 km2 (95% CrI: 4.1–9.3) and
10.8 individuals/100 km2 (95% CrI: 6.2–19.9) when applying effective sampling areas derived from estimates of mean
maximum distance moved and half mean maximum distance moved, respectively. Daily detection probabilities of males
(0.00038; 95% CrI: 0.00025–0.00052) were more than double that of females (0.00018; 95% CrI: 0.00010–0.00029),
presumably due to sex-specific differences in space use. Tapir abundance was positively correlated with elevation, corroborating
other findings from Thailand but contrasting with those from Sumatra. Tapirs were primarily nocturnal, with
88% of detections between sunset and sunrise. These findings highlight our study area’s importance as a potential tapir
population stronghold and demonstrate the utility of bycatch data for studying wildlife populations. We discuss our results
in the context of tapir ecology and provide recommendations for future surveys. This study enhances our understanding
of this endangered species and emphasizes the need for targeted research to guide evidence-based conservation.