2026 Volume 51 Issue 4 Pages 413-421
On Chichijima Island in the Ogasawara Islands, where ecological impacts of invasive rodents are of concern, this study aimed to quantitatively evaluate the feeding preference and feeding pressure of the Rattus rattus on plant stems and leaves. We conducted route censuses to record shoot damage caused by R. rattus, calculated species-specific palatability indices, and compared their distributions among endemic, cosmopolitan, and alien plant species. We also defined local feeding pressure as the palatability threshold above which plant species experienced shoot damage and calculated feeding pressure for each survey route. We found that some endemic species exhibited particularly high palatability. The median of the palatability frequency distribution among plant species did not differ significantly among species groups. In contrast, the presence of highly palatable endemic species suggested greater interspecific variability in palatability within endemics, although this tendency was weak. Feeding pressure along survey routes tended to be higher at higher elevations. Because remnant dry scrub forests at higher elevations on Chichijima Island include many highly palatable plant species, vegetation type may be associated with R. rattus density. This study quantitatively evaluated the impacts of invasive rodents on vegetation on an oceanic island and provides insights relevant to future conservation and management.
