Wood Mice Utilize Understory Vegetation of Leafless Dead Dwarf Bamboo Culms as a Habitat and Foraging Site

In this study, we conducted a field survey in Aichi Prefecture, central Japan, to clarify whether rodent activity is affected by the presence or absence of dead culms of the dwarf bamboo Sasa borealis, a species characterized by a 120-year cycle of large-scale flowering, seeding, and dying. We found that a relatively larger number of wood mice, Apodemus speciosus and Apodemus argenteus, were caught using Sherman live traps in areas with dead S. borealis culms than in areas lacking the culms, thereby indicating that S. borealis culms, even if dead and leafless, can function as shelters in which the mice can evade predation. However, in the years when A. speciosus was abundant, A. argenteus avoided areas inhabited by A. speciosus and was restricted to areas lacking dead culms, which were devoid of shelter. A feeding experiment using Castanea crenata acorns clearly revealed that a larger number of acorns were foraged by mice in areas containing dead culms. Moreover, in the area with dead culms, the mice preferentially removed sound acorns prior to taking acorns that had been vacated by infesting moth larvae. These findings indicate that the shelter function of dead culms enables mice to carefully select sound acorns, which are nutritionally more beneficial than those that have been infested by moth larvae.