Habitat factors affecting the geographic size variation of Japanese moles.

Abstract

Japanese moles of the genus Mogera show remarkable geographic variation in body size. In order to determine which habitat factors affect them, 260 specimens of Mogera imaizumii were collected from 27 localities, 280 specimens of M. wogura were collected from 23 localities, and 41 specimens of M. tokudae were obtained from two localities. The relationships between size, geographic location and seven habitat factors consisting of habitat (rice field) area, soil hardness, and five meteorological components, were analyzed. All three species showed a positive correlation between greatest skull length and habitat area. Populations of M. imaizumii from areas with heavy snow were significantly smaller than those from areas with little or no snow and this variation was also explained by the negative correlation with total annual precipitation. In addition, the size of M. imaizumii varied positively with the variation in annual mean temperature. In the correlation between skull size of M. wogura and habitat area, there was a significant difference in the Y-intersept between the populations from central Honshu and those from southern Honshu, Shikoku and Kyushu. This variation was well explained by the negative correlation between skull size and mean minimum temperature. This variation, however, was not constant across all populations examined, because M. wogura were smaller in narrow valleys, even where mean minimum temperatures were low.