Counting Bats at Kasanka: Developing and Evaluating an Automated YOLO+TRex Video-Analysis Pipeline

How reliably can we count bats from videos of their evening emergence? At Kasanka National Park, Zambia, recordings of straw-coloured fruit bats (Eidolon helvum) provide an opportunity to evaluate automated counting under challenging conditions. This talk presents the development and evaluation of a pipeline combining YOLO for bat detection and segmentation, TRex for tracking their movements, and a counting step that measures net crossings of a virtual line. Its outputs were compared with manual reference counts and an existing automated method developed by Koger et al., using the same seven-second video segments. Across the evaluated sample, the YOLO+TRex pipeline systematically underestimated net crossings relative to the manual reference counts, while the Koger method was closer to the reference in most cases. The talk discusses the pipeline’s current limitations and how targeted validation of its detection, tracking, and counting stages could guide further development.