Communal nesting of the small Japanese field mouse in tree cavities in early spring

Abstract

The small Japanese field mouse, Apodemus argenteus, is a semi-arboreal rodent that breeds in tree cavities. For this study, however, we observed its cavity-nesting behavior during the non-breeding season. In urban and riparian forests in April on the island of Hokkaido, Japan, we found two nesting cavities housing five and ten adult-like mice, respectively. Dissolutions of communal nesting advanced in late April. We consider that one reason for communal nesting is heat retention while overwintering, as is common among rodent species. Our results expand knowledge of cavity use by the mice during the non-breeding season. Previous studies of cavity use by these mice were used nest boxes as artificial substitutes for tree cavities, which can provide inaccurate information of cavity use by the mice during non-breeding season since rodent species often avoid using these boxes in the cooler temperate season. Since nest boxes are used for studies for other mammals and birds, our results suggest that they should be studied in conjunction with cavity observation to accurately explain animals’ cavity use.