Multi-surveyor capture-mark-recapture as a powerful tool for butterfly population monitoring in the pre-imaginal stage

For many elusive insect species, which are difficult to cover by standard monitoring schemes, innovative survey methods are needed to gain robust data on abundance and population trends. The recording of pre-imaginal butterfly life stages provides great potential for ecological studies and conservation monitoring. However, using counts of pre-imaginal stages for quantitative research requires detection probability to be determined.
We tested different removal and capture-mark-recapture (CMR) approaches to determine the detection probability for overwintering larvae of the endangered nymphalid butterfly Limenitis reducta. Classical removal and CMR studies require movement of the organisms under study but in our approach, we replaced movement of the study organisms by random movement of multiple different surveyors. The study was conducted in three plots within a spruce clear-cut in the 'Alb-Donau' region, Germany.
Our dataset provides detection data of nine/ten different surveyors per st...