Ecological drivers of garden dormouse (Eliomys quercinus) occupancy in a human modified landscape in Germany

The garden dormouse (Eliomys quercinus) is an understudied mammal species
endemic to Europe. Once distributed widely across the continent, its
eastern populations have significantly declined, with the species now
found in only 50% of its former range. In Germany, it also occurs in
spruce forests in low mountain ranges. However, this habitat has recently
been lost due to bark beetle infestation following a prolonged period of
drought. In some places, not only are the dead trees removed, but also all
the branches and topsoil.  We assessed habitat requirements of a
garden dormouse population in such a changing habitat in the Harz
Mountains, Germany. To assess garden dormouse occupancy, we conducted
transect surveys using footprint tunnels in July and October 2022 for the
presence of garden dormice. Additionally, we measured covariates such as
coverage of tree, shrub, and herb layers, as well as deadwood, soil
characteristics, and reforestation. Using single-season occupancy
modelling, we evaluated the effects of these habitat covariates on the
occupancy of the garden dormouse.  Our results indicated that
garden dormouse occupancy was negatively affected by herb cover, but
positively associated with plant successional stages. Furthermore,
occupancy of the garden dormouse was positively coupled with the
occurrence of the hazel dormouse (Muscardinus avellanarius). Detection
probability increased with higher weekly minimum temperatures. 
For the conservation of garden dormice in low mountain ranges like the
Harz, practical measures should include establishing interconnected forest
edges and strips. Moreover, we suggest adopting a dynamic, mosaic approach
to felling, avoiding topsoil removal, and promoting regeneration that
fosters semi-open successional habitats as essential strategies.