New distribution records and temporal activity of endangered forest musk deer ( Moschus berezovskii ) in karst forests of northern Vietnam

The forest musk deer ( Moschus berezovskii ) is an Endangered and elusive ungulate whose distribution in Vietnam remains poorly documented. Using targeted camera-trap surveys guided by field signs and local knowledge, we documented new distribution records from three karst protected areas in northern Vietnam: Kim Hy Nature Reserve, Than Sa–Phuong Hoang Nature Reserve, and the Cao Vit Gibbon Species and Habitat Conservation Area. These records extend the species’ confirmed distribution beyond the only previously verified locality at Huu Lien Nature Reserve. Camera traps yielded 26 independent detections, with relative abundance indices ranging from 0.39 to 1.93 detections per 100 trap-nights. Minimum latency to first detection ranged from 2 to 11 days, and required survey effort varied from 154 to 762 trap-nights among sites. Detection times indicated a predominantly crepuscular activity pattern, with peaks during early morning and late afternoon. Our findings demonstrate that forest musk deer persist in multiple karst forest fragments in northern Vietnam and provide the first baseline information on their activity patterns, highlighting the importance of updated distribution data and ecological information for protected-area management and conservation planning.