Restoring fragile wings
Ronja’s project aim to studyMarsh fritillary’s landscape occupancy and population recovery 7 years after an extreme drought.
Main Research Questions
- What is the occupancy of suitable habitat patches?
- What are the population dynamics over time?
- How does the species recover in previously extinct patches?
- What is the impact of weather events on population dynamics and habitat preferences?
Background
The Marsh Fritillary is a threatened butterfly across Europe. Its one-year life cycle consists of three stages: eggs, larvae, and butterflies. Eggs are laid under leaves of the host plant (Succisa pratensis), larvae spin silken nests around host plants before hibernating and live as butterflies between late May and late June in Sweden.
Methods
Area: Marsh fritillary will be surveyed near Slite on Gotland during the summer of 2025 (end May- end June). In this area, the habitat of the Marsh fritillary composes of wet parts of unfertilized calcareous wet grasslands that in most places remain naturally open due to poor soil and slow accumulation of humus. In this habitat, vegetation is sparce, making the Succisa pratensis one of the few plants surviving.
Figure 1: Location of study landscape (a) and the spatial location of habitat patches (b), red circles show the CMR sites.
Methods: The methods will include a capture-mark-release (CMR) study during the flight period to assess local population sizes. Individuals will be captured, marked and released along irregular routes focused to cover suitable habitat that the species utilises. Adults will be marked using a permanent marker pen and immediately released at the point of capture. Temperature, light intensity and proximity to the forest will be recorded with temperature-loggers to study butterfly activity in relation to daily temperature patterns. These CMRs will take place at Filehajdar and Högstensvät, close to Slite (fig. 1) covering a population that went extinct due to the 2018 drought (upper left corner). Knowledge about the recovery of the Marsh fritillary is useful for future recovery projects.
During the peak flight period (3 May – 13 June), patch occupancy across the entire habitat patch network will be recorded (see figure 1). Vegetation and hostplant abundance are measured, using transects, to provide a more detailed habitat quality than the current data can give. The species, height, abundance and largest leaf size will be recorded and pictures of the vegetation will be taken to be analysed partly with help of AI later.
The data gathered from this research will be compared to data collected in previous years and can contribute to the existing knowledge about the Marsh fritillary. This will include a follow up of the habitat patch cluster that went extinct after the 2018 drought (Högstensvä), which has not been done since 2020. Insights into population dynamics, habitat utilization, and butterfly behaviour will directly inform restoration strategies. For example, understanding host plant requirements and habitat preferences can guide vegetation management, data on population resilience can help predict the response to environmental stressors like drought and improved ecological knowledge can support restoration efforts, enhance habitat connectivity and biodiversity conservation.
