Demographic insights into Lopinga achine populations in alluvial forests: implications for conservation in non-grazed woodlands

Butterflies inhabiting open forests are declining across Europe, but the knowledge on their population ecology is still limited. The Lopinga achine is an endangered species, occupying open forests that are typically maintained by extensive forest grazing or coppicing. Previous studies on the ecology of L. achine were restricted to certain geographical areas, habitat and management types, thus their conclusions may not be transferred to all parts of Europe. To inform conservation strategies for this species, we investigated populations in non-grazed alluvial forests in western Hungary and gathered demographic and movement data using capture-mark-recapture. We marked 165 butterflies in Alsószölnök and 130 in Szakonyfalu, with more males than females in both populations. Total population sizes were estimated at 311 (95% CI 257–398) in Alsószölnök and 264 (95% CI 196–386) in Szakonyfalu, with 1.43 and 1.11 male ratios, respectively. In Alsószölnök, apparent survival declined over the season, and male recapture probability increased with age. Most individuals moved less than 150 m, but four males dispersed more than 1,000 m between the sites. We obtained robust estimates of population size and survival in L. achine, providing a baseline for future demographic, behavioural, and conservation-management studies. Although population sizes were low compared with other European studies, their national conservation value remains high. Targeted habitat management should focus on maintaining a semi-open forest structure, we propose bark girdling primarily on non-indigenous tree species. The distance between suitable habitat patches should not exceed 100 m.