Functionality of oak log wood mould boxes as artificial habitat for the hermit beetle (Osmoderma eremita)

Abstract Artificial habitats are used worldwide in conservation efforts to protect endangered species. Wood mould boxes are designed to serve as a suitable artificial environment for saproxylic beetles, whose natural habitat are old hollow trees. We evaluated the functionality of wood mould boxes made of oak logs for the hermit beetle ( Osmoderma eremita ). We tested if characteristics of the boxes (wood mould volume, pH, and moisture and outer diameter) affected the number of larvae found inside. In addition, we tested if transplantation of larvae from nearby fallen trees into the boxes affected abundance. In 16 of the 26 studied boxes, we found more than one larva, which indicates that the basic design using hollowed-out logs provides a suitable artificial habitat for the hermit beetle. There was a positive relationship between box diameter and abundance and a negative relationship between wood mould pH and abundance. Humidity and wood mould volume had no major effects. Transplantation of larvae into the boxes had a weak positive effect on abundance. Implications for insect conservation Our study shows that using wood mould boxes as artificial habitat for the hermit beetle may prove valuable before forest management can secure enough natural habitat, and that transplantation of hermit beetles as a conservation measure warrants further investigations.