Flight behaviour of a threatened butterfly at edges between high- and low-quality habitat

Abstract Butterfly populations in Europe are declining, necessitating efficient conservation strategies. Understanding butterfly behaviour in relation to habitat quality is important, and one aspect is flight behaviour at habitat edges. This study investigates flight patterns of the marsh fritillary (Euphydryas aurinia) in relation to edges between intensively grazed and ungrazed habitat on Gotland, Sweden. We also examine the small-scale habitat utilization in relation to the abundance of host and nectar plants. Observations were conducted across four sites, using 40 × 40 m plots situated in ungrazed habitat with one edge facing grazed habitat. We recorded the proportion of butterflies that crossed the edge into grazed habitat compared to interior edges and the proportions that returned. By dividing each plot into 16 subplots, we quantified small-scale habitat preferences based on flight trajectories. In total, we followed 208 individuals. Results showed that butterflies were significantly less likely to cross edges into grazed areas, but there was no significant difference in return behaviour. Utilization of subplots increased with increasing abundance of the host plant (Succisa pratensis).