Monitoring tropical forest ungulates using camera-trap data

Tropical forest ungulates are poorly known and, despite their ecological and conservation significance, there are few studies on their density and abundance. I estimated densities of lesser oriental chevrotain Tragulus kanchil in the Southern Cardamom National Park, south-west Cambodia using camera-trap encounter rates and fitting a random encounter model (REM) that does not require individual identification of animals. This represents the first use of REM on forest ungulates in mainland tropical Asia and provides the first density estimate for any chevrotain species in mainland South East Asia. Sixty-five camera-trap stations generated 501 encounters of lesser oriental chevrotain across >8200 camera-trap nights within a systematic random camera-trap grid of 200 km(2) in the Southern Cardamom National Park. Density of lesser oriental chevrotain was estimated at between 57 and 98 (X 81) individuals per km(2). The random deployment of camera-traps, a prerequisite of the REM, did not prevent the detection of the majority of ground-dwelling large mammal species likely to be present in the study site. Despite its slow uptake by field conservationists, the REM may have potential for monitoring tropical ungulates particularly in dense evergreen forest where other methodologies, for example, distance-based line transect sampling are unsuitable.