Authors: Hendel, Anna-Lena; Winiger, Nathalie;Zielewska-Büttner, Katarzyna ;Adler, Petra;Ganz, Selina;Braunisch, Veronika;

Enhancing structural complexity in multifunctional forests, e.g. through retention forestry, is an important strategy to support forest biodiversity, yet its evaluation requires area-wide and sufficiently precise information on key structural elements and associated species’ habitats. As bats respond to forest structures at multiple spatial scales, we tested the importance of forest structure variables derived from stereo-aerial photographs in relation to topographic, climatic and land-use variables for studying bat habitat selection inside forests.
Acoustic data was collected on 135 plots in the Black Forest, Germany. Species distribution models were calibrated for 8 bat species or acoustic groups, thereby identifying the best-performing scale (stepwise increasing radii between 50 - 1000 m around each location) for each predictor and species (group). Forest structural variables such as the percentage of standing dead trees, tree volume and forest height heterogeneity best explained bat habitat selection, mostly at small scales (50 - 100 m), contributing on average 46 % to overall model performance. To assess the benefit of retention forestry for bats, we finally compared key structural variables and the predicted habitat suitability across forests with and without retention measures. The results highlight the value of remotely sensed structural variables to identify areas for bat conservation.