A case of arboreal nest building in the small Japanese field mouse (Apodemus argenteus)

To better understand the arboreal activity of small mammals, we focused on the arboreal nest-building behaviour of Apodemus argenteus. Using a camera trap, we found that a mouse took 18 days to build a nest in a tree cavity. For a few days during the nest building period, the mouse intensively carried nesting materials (leaves) to the cavity, though not regularly. The mouse did not constantly carry nesting materials, but rather showed two peaks working activities at 02:00 and 22:00. Judging from the uneven working pattern, its nest-building behaviour may depend on environmental condition such as meteorological factors.