Drey site selection of Japanese squirrels in the cool temperate zone: evaluation at multiple spatial scales

: In this study, we clarified the drey site selection of Japanese squirrels living in cool temperate zone at three spatial scales (landscape, stand, and tree). The survey was conducted in a forest area of the Shonai region, Yamagata Prefecture. From March to May 2020, we searched for globular nests along seven survey routes. We also conducted a plot survey from August to November 2020 to investigate the forest structure of some drey trees found in the route survey. To examine selectivity at the landscape scale, we analyzed the relationship between drey sites and environmental factors (topography, distance from bodies of water, and forest type). At the stand-scale, we analyzed whether there were differences in mean tree height, mean diameter at breast height (DBH), and number of standing trees between drey and non-drey plots. At the tree scale, we analyzed whether there were differences in tree height, DBH, and species composition between drey and non-drey trees. The results of the landscape-scale analysis showed that Japanese squirrels significantly selected deciduous and evergreen coniferous forests as drey sites, with evergreen coniferous forest being relatively more important. Plots with fewer standing trees were selected as drey sites at the stand-scale. Trees with higher height and a larger DBH were significantly selected at the tree scale. The drey selection of Japanese squirrels differs depending on the spatial scale; therefore it is important to evaluate drey site selection at multiple scales.