Impact of wild boar (Sus scrofa) rooting succession on grasshoppers (Orthoptera) in abandoned calcareous grasslands

Abstract

Many European insect species are bound to open habitats, hence disturbances that reset succession are important for their conservation. These can be employed in the form of low-intensity management or, alternatively, natural processes. Rooting by wild boar ( Sus scrofa ) is an example of such a natural process. In this study, we investigated if and how boar rooting influences Orthoptera (grasshoppers and crickets) communities in calcareous grasslands. We compared three successional stages in abandoned calcareous grasslands in Hainich National Park, Germany: fresh rootings, old rootings and the matrix. We tested for differences in microhabitat, Orthoptera abundance, species composition and demography. We found that crickets and bush-crickets (Ensifera) preferred late successional stages in May and June, whereas grasshoppers and groundhoppers (Caelifera) preferred early successional stages in May, whereas they did not show any preference in June. We found two mechanisms through which rooting by wild boar supported Orthoptera diversity: (1) different microhabitats support different habitat specialists with different life cycles. Habitat mosaics created by wild boar are thus more diverse than just undisturbed grassland and (2) the most diverse microhabitat, characterised by the highest species richness, was created by wild boar. Additionally, our observations also indicated that successional mosaics offer habitats for species requiring different microhabitats throughout their life cycle. Implications for insect conservation: Our results indicate that, at this density, wild boar can help to sustain Orthoptera biodiversity in calcareous grasslands. We advise to take the beneficial role of wild boar into consideration in conservation measures and wild boar population management.

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