Density estimations of the Asiatic black bear: application of the random encounter model

It is difficult to assess the population status of large terrestrial carnivores due to their low density. Recently adopted camera-trap techniques allow us to investigate many aspects of animal ecology and conservation and are widely used in wildlife population estimation. In this study, we applied the random encounter model (REM) to estimate the density of Asiatic black bears (Ursus thibetanus) in Shirakawa Village, Gifu Prefecture, Japan, from May to October 2018. We installed 24 sensor cameras in the study area. Movement speeds of seven global positioning system (GPS)-collared bears were tracked from 2008 to 2018. The population density of bears in Shirakawa Village was estimated to be 0.55 bears/km(2). To apply the REM method to Asiatic black bears, we recommend (1) installing more than 30 or 40 sensor cameras and implementing the REM method in a period of 3 weeks before the late summer season (i.e. late August), after the completion of the hibernation period and when a closed population is easily maintained; and (2) correcting the distance moved by the target animal species when using GPS telemetry with a low fixed interval.