Estimating animal density without individual recognition using camera-trap-derived information

Nakashima, Fukasawa, and Samejima proposed the Random Encounter and Staying Time (REST) model, which estimates density from the number of detections and the time animals remain within a defined detection zone, both measured directly from camera-trap video or sequential images. Unlike the Random Encounter Model, REST does not require external estimates of animal movement speed, instead using staying time captured by the cameras themselves. This makes it attractive where day-range data are unavailable. Validated against known densities, the method performed well and reduced reliance on auxiliary parameters. REST has become a popular recognition-free estimator for unmarked mammals in camera-trap studies. The paper is a notable methodological reference advancing practical density estimation without individual identification.