On Wood Mice (Voles) in Yamagata Prefecture

II. The Distribution of Wood Mice according to Different Types of the Forests

Abstract

The investigation was carried out in forests of altitudes ranging from 550 to 600 meters on the eastern side of Mt. Shiratake (in Yamagata Prefecture) of which the highest peak is 992 meters above sea level. The forests selected are composed of Japanese red pine (Pinus densiflora SIEB. et ZUCC.), Japanese ceder (Cryptomeria japonica D. DON.), Japanese larch (Larix leptolepis GORD.) and broad leaved deciduous trees. Two types of forests were selected, namely young forests and older forests, the former about 3-8 years old while the latter 20-50 years old. The collection of voles was made at 8 different pre-selected spots in each forest by means of snap traps with sweet potato as the bait. The results obtained are as follows. Microtus montebelli was plentiful in the sunny places of young forests composed of Japanese red pine, Japanese ceder, Japanese larch and broad leaved deciduous trees. However, it was not found in the older Japanese larch forests or in the broad leaved deciduous tree forests. In general more individuals were collected in the young forests than in the older ones. Clethrionomys andersoni were frequently found in the moist grounds of the older forests of Japanese ceder, Japanese larch and broad leaved deciduous trees. Generally, larger number of individuals were collected in younger forests than in the older ones. None was caught in forests composed of Japanese red pine. Apodemus speciosus was very common as in all other forests in Yamagata Prefecture. However, no close relation seems to exist between the habitat of this vole and the forest types concerning tree kind and tree age. A. speciosus were very frequently found in the forest of Japanese larch forests. They were also found in broad leaved deciduous tree forests where M. montebelli was rare. Apodemus geisha were collected more in the young than in the older of Japanese red pine, Japanese ceder and Japanese larch forests. Only this species was more frequent in the older forests than in the younger ones of broad leaved deciduous trees. None was caught in older forests of Japanese red pine.