Abstract
The decline of open habitats in Europe, such as semi-natural grasslands and heathlands, has caused a general decline in biodiversity, which has been well documented for butterflies. Current conservation practices often involve grazing by domestic livestock to maintain suitable butterfly habitats. The extent to which wild ungulates may play a similar role remains largely unknown. Through their rooting activity, wild boar could be effective to reduce grass encroachment and restore pioneer microhabitats that are vital to many grassland insects in temperate climates. Here, we assessed the microhabitat requirements of Pyrgus malvae, an endangered butterfly of heathland and grassland habitats in the Netherlands, with special attention for the influence of wild boar rooting. To date, oviposition site selection of this species has concentrated on calcareous grasslands, whereas we also include heathlands. Overall, larval occupancy was higher in warm, open and sparsely vegetated microhabitats, which supports earlier findings. In heathland, microhabitat occupancy was positively affected by bryophyte and litter cover. In heath-grassland mosaic, microhabitat occupancy was also influenced by bryophyte and litter cover, but in addition low grass cover increased occupancy by favouring host plants. In grassland, only low grass cover and host plant cover determined microhabitat quality. Across all habitats, occupied microhabitats were characterized by lower vegetation as well as higher average daytime temperatures than unoccupied microhabitats. We discovered that wild boar play an important role in reducing grass cover by shallow rooting in grass patches, thereby increasing host plant availability. Hence, wild boar may have an added value in maintaining and restoring P. malvae microhabitats in grassland habitats in addition to grazing by domestic livestock.
Highlights
The shift from traditional agricultural practices to agricultural intensification, afforestation, and abandonment of land are major drivers in the loss of open habitats, such as seminatural grasslands and heathlands (Bakker and Berendse 1999; Poschlod et al 2005; Streitberger and Fartmann 2016)
Single eggs are laid on host plants and P. malvae caterpillars spin leaves together to form tents which provide them with a buffered microclimate and protection against predation (Brereton 1997)
Occupied P. erecta host plants only occurred in the heathland plot (H)
Summary
The shift from traditional agricultural practices to agricultural intensification, afforestation, and abandonment of land are major drivers in the loss of open habitats, such as seminatural grasslands and heathlands (Bakker and Berendse 1999; Poschlod et al 2005; Streitberger and Fartmann 2016). Semi-natural grasslands and heathlands are considered to be hotspots for biodiversity in Europe (Veen and Jefferson 2009) and are the preferred habitats for the majority of European butterfly species (Munguira et al 2009; WallisDeVries and van Swaay 2009). As a result of habitat loss, population declines have been observed for almost a third of the butterfly species in Europe (van Swaay et al 2010). Journal of Insect Conservation (2018) 22:51–59 may require a variety of microhabitats to provide the vital resources required during subsequent life stages of their life cycle (Dennis et al 2006; Wynhoff et al 2008). Elucidating the favourable conditions for larval development of threatened species may provide new insights for suitable habitat restoration and management (WallisDeVries et al 2016)
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