Spherical nest of the harvest mouse and surrounding vegetation of a riverbed in western Nagoya

Abstract

Recent research reports that harvest mice (Micromys minutus) are commonly found inhabiting wet areas with dense grass (Poaceae) and sedge (Cyperaceae) vegetation in low-lying grasslands, rice and other crop fields, fallow fields and marshland areas. On the other hand there are few studies reporting their frequent use of flood plains and embankments nationwide and only a very limited amount of research has been focused on how vegetation influences their nesting behavior in flood plains and embankments. Furthermore, no work has been conducted in urban areas to investigate the relationship between habitat use characteristics and covering vegetation types. This study aims to investigate the spherical nests of harvest mice in flood plains and embankments of Shonai River, which flows through western Nagoya, Aichi, Japan, and analyze the relation between the distribution of nests and the surrounding vegetation in order to reveal the habitat conditions of harvest mice in urban regions. The results show that the harvest mice were present in three main habitat categories within the 20-meter buffer zones surrounding nests. One of these categories was grassland covering 754.4– 860.9 m² (65.1–79.3%) of each buffer zone. These areas that were assumed to be suitable habitat were dominated by Johnson grass (Sorghum halepense) and Amur silvergrass (Miscanthus sacchariflorus). Another suitable habitat category contained areas where the buffer circles were dominated by artificially bare ground, urban parks and sports grounds containing grassland in only 114.2–297.8 m² (9.2–30.1%) of the circle. This research suggests that in flood plains under intense human influences in urban areas like Nagoya, harvest mice can make adaptive use of limited amounts of favored vegetation for nesting.