Foraging strategy of wood mice for undamaged and moth-infested Castanea crenata nuts on forest floor

This study investigated the foraging strategy of wood mice for undamaged Castanea crenata nuts and those with exit holes from moth larvae (EH nuts) on the forest floor in 2022 and 2024. Mice were captured using live traps, and nut infestation status was assessed. A behavior experiment was also conducted to observe the mouse responses to nuts. In both years, Apodemus speciosus and A. argenteus were observed. Throughout the entire study period, EH nuts accounted for a large proportion of insect-damaged nuts. Most EH nuts (95/100) showed reduced contents (i.e., mostly cotyledons) (0–40%) and internal discoloration. Nonetheless, almost all nuts were removed overnight, with undamaged nuts removed earlier than EH nuts. Mice sniffed or clutched approximately 50% of the nuts before removal, suggesting olfactory-based evaluation. A higher proportion of undamaged nuts was removed after examination than without examination. These results revealed that although most EH nuts have low feeding value, they remain an important food resource. Mice use olfactory cues to avoid EH nuts and select undamaged nuts; however, the additional evaluation time may increase their risk from predators and competitors.