... A preliminary survey on nest cavity use by Siberian flying squirrels, Pteromys volans orii , in forests of Hokkaido Island, Japan . ... To broadly understand what nest cavity is selected by P. volans orii in mountainous areas, we preliminary surveyed cavity resources in natural forests of Hokkaido. All nest cavities were on live-trees. ... To understand these usefulness as P. volans orii habitat, we made a preliminary comparison of cavity resources in two different forests common in Hokkaido. ...