Landscape properties and density dependence shape the movement patterns of three threatened butterflies

Context

Conservation of endangered species necessitates an in-depth understanding of their ecological requirements. Particularly in landscape ecology, the behavioural tendencies of threatened butterfly species in Gotland, a biodiversity-rich island in the Baltic Sea, become crucial.

Objectives

The primary aim of this study was to elucidate the movement patterns of three threatened butterfly species—Euphydryas aurinia, Parnassius apollo, and Phengaris arion—in Gotland and to identify the influence of specific land characteristics on these patterns.

Methods

Our study, conducted from 2017 to 2020 across 60 km² in Gotland, involved detailed capture-mark-recapture (CMR) efforts of 29,584 captures including 16,223 unique butterflies. We investigate the departure and arrival events of butterflies, specifically focusing on the associations between movements when individuals leave or enter a hectare grid different from their previously recorded location and key landscape features: open vegetated land, ground moisture, and forest cover. We model landscape features to examine the interplay between these and butterfly movement patterns, providing insights into preferred landscape features and conservation strategies.

Results

Among the 4821 arrivals and 5083 departures documented, the species exhibited differential responses to the evaluated habitat features. Both E. aurinia and P. apollo displayed a positive density-dependent dispersal, while P. arion’s movements were not significantly associated with any of the examined habitat features. Landscape properties like open vegetated land and ground moisture index statistically influenced the likelihood of arrival and departure.

Conclusions

The study accentuates the relationship between land cover and the behavioural tendencies of the subject butterfly species. It has broader implications for the targeted habitat management strategies that would benefit threatened butterfly populations in Gotland.