Mammal and bird species using cavities among forests of different ages on Okinawajima Island in the Ryukyu Archipelago, Japan

Various animals use tree cavities in the northern forest of Okinawajima Island in the Ryukyu Archipelago. However, the cavity characteristics and forest types used by cavity users are not well known. The aim of this study was to reveal the cavity users in natural forests of different ages in northern Okinawajima Island. Camera trap surveys were conducted to identify the utilization of cavities in four <i>Castanopsis sieboldii</i> dominated forests; one 40-year-old, one 70-year-old, and two mature forests. Only a few cavities were recorded in the 40-year-old forest and these locations were limited to the lower part of the trees. Consequently, cavity users were limited to two ground-foraging bird species. In contrast, cavities of various sizes were located at various heights above the ground in the other three types of forests, although endangered mammals such as Ryukyu long-furred rat (<i>Diplothrix legata</i>) and Ryukyu tube-nosed bat (<i>Murina ryukyuana</i>) only used cavities in mature forests. The greatest number of cavity-using bird species were recorded in the 70-year-old forest, and a Ryukyu robin (<i>Larvivora komadori</i>) built a nest in a cavity. These results show that mature forests provide various types of cavities with various functions which are important for diverse animal taxa, and that cavity users differ among forests of different ages. Furthermore, it was observed that cavity availability and use does not recover in 70 years. Cavity users should be considered in forest management not only in the core area, but also in the buffer zone of the protected areas in the future.