Long-distance movements, large population sizes and density-dependent dispersal in three threatened butterfly species

1. This study investigates the ecology of three threatened butterfly species on a 60 km2 site in Gotland, Southeast Sweden, using mark-recapture methods from 2017 to 2020. 2. Nearly 30,000 captures were recorded, with average lifespans of 6 days for Euphydryas aurinia (Lepidoptera: Nymphalidae) and Parnassius apollo (Lepidoptera: Papilionidae) and 2 days for Phengaris arion (Lepidoptera: Lycaenidae). 3.Population size, density and maximum flight distances varied between species, with E. aurinia at 7.2 km, P. apollo at 6.4 km and P. arion at 2.5 km. 4.Movement data showed the lognormal kernel fit better than gamma, negative exponential and half-normal kernels for distance travelled per time unit across species and sexes. 5. Generalised linear models revealed significant positive density-dependent emigration and negative density-dependent immigration in all three species. 6. Despite available suitable habitats, these species face threats from limestone quarry expansions, agricultural intensification, modified forestry practices, natural succession and climate change, highlighting the need for proactive conservation and strategic habitat management.