Movements of a Specialist Butterfly in Relation to Mowing Management of Its Habitat Patches

Simple Summary European grasslands and their rich biodiversity have been shaped by humans for centuries through grazing and mowing. While mowing is perceived as good practice for sustaining meadows and conserving butterflies in the long term, the mowing event itself may have negative short-term effect on butterflies. A mosaic of different mowing regimes allowed us to explore this effect while studying movements of a wet meadow specialist butterfly, the scarce large blue. The main results showed that mowing negatively affected butterfly population size and increased butterfly dispersal probability. However, the increased dispersal led only to short-distance movements and was apparently undertaken by individuals not adapted well enough to emigrate. In turn, a larger area of habitat patch was found to be beneficial for promoting long-distance dispersal and hosted bigger butterfly populations. This means that large and unmown meadows support more viable populations and provide better connection among local populations. They are particularly important for persistence of the studied butterfly in a fragmented landscape. Thus, conservation programmes should aim to retain enough unmown habitat each year and to preserve large and interconnected habitat fragments. Over the centuries, mowing and grazing have been crucial for sustaining populations of grassland insects and their overall diversity in Europe. While long-term positive effects of mowing have been studied in more detail, little is known about the direct impacts of mowing on adult butterflies. Here, we explore how different habitat management (mown, recovered after mowing and unmown) affects movements and population estimates of the endangered specialist butterfly Phengaris teleius. The results showed higher dispersal probability from mown (22%) and recovered meadows (16%) than from the unmown ones (9%). However, mowing shortened the average dispersal distances (mown = 102 m, recovered = 198 m, unmown = 246 m) and reduced butterfly population size. In contrast, a larger area of the habitat patches promoted long-distance dispersal and sustained larger populations. We hypothesise that mowing caused depletion of resources and triggered dispersal of poorly adapted individuals. This behaviour is maladaptive and could lead to higher dispersal-related mortality; thus, mowing should be avoided before and during the butterfly flight period. This study suggests that the species' persistence in a fragmented landscape depends on large, unmown and interconnected habitats that support more viable populations, promote long-distance dispersal, and enable (re)colonisation of vacant patches.