Distribution of small mammals and fluctuation of their trap success in the Oze District, northeastern Honshu, Japan

Abstract

Fauna of small mammals was investigated on fourteen sites of the Oze district bordering Niigata, Fukushima and Gunma Prefectures in northeastern Honshu, Japan. Surveys were conducted from August 1985 to July 1999, and carried out from early July to early August of each year. Small mammals were captured using small snap traps (Panchu, PMP size) through montane broad-leaved deciduous forest zone (alt. 1,000m) to subalpine coniferous forest zone (alt. 1,900m). By 16,800 trap nights in total, small mammals collected were one species of Insectivora (Urotrichus talpoides 22) and five species of Rodentia (Eothenomys andersoni 7, E. smithii 92, Microtus montebelli 17, Apodemus argenteus 564 and A. speciosus 669). 1,371 small mammals in total was obtained and trap success was 8.2%. All the U. talpoides were collected in areas of alt. under 1,600m but the total capturing rate of this species was remarkably low. Further, totally seven individuals of E. andersoni were captured through the trapping surveys. Of them, six individuals were obtained in areas of alt. over 1,500m besides in the north side of the Ozegahara-Ozenuma line. In addition, all the specimens of E. smithii were collected in areas of alt. under 1,600m. On the basis of the collection data, E. smithii were captured equally in total number between the north on south sides of Ozegahara-Ozenuma line, 50 individuals and 42 ones, respectively. Apodemus argenteus and A. speciosus were dominant compared with other species throughout most of the study areas. Trap success of A. argenteus was significant at lower areas of montane broad-leaved deciduous forest zone (alt. 1,000-1,300m) than at the upper areas (alt. 1,300-1,600m). On the other hand, trap success of A. speciosus was not significantly different between the two areas. Annual changes of trap success of A. argenteus were relatively lower, but those of A. speciosus were higher. Trap success of A. speciosus was highest in the year of 1985 and 1994 in all survey areas. The high trap success was attributable to the masting of beechnut carried out in the last year.