著者

宮尾 嶽雄 両角 源美 両角 徹郎

出版者

社団法人日本動物学会

雑誌

動物学雑誌 (ISSN:00445118)

巻号頁・発行日

vol.75, no.4, pp.98-102, 1966-04-15

被引用文献数

2

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This paper deals with the seasonal variation of sex ratio, body weight, number of pregnant females and testicle size in the vole, Microtus montebelli. They were collected in the period from May, 1964 to September, 1965 in the montane zone (alt. 1,400-1,500m) on Mt. Yatsugatake in Honshu. The total number of specimens collected was 335. They are 33 Apodemus speciosus, 5 Apodemus argenteus, 272 Microtus montebelli, 22 Urotrichus talpodes and 3 Sorex shinto. Microtus montebelli was found exclusively in the grassy area of the montane zone. The number of female Microtus montebelli was larger than the males through months except for the months of May and October. Histograms of the body weight tend to indicate that voles grow rapidly in spring and reach maturity in months ranging from May to August. Breeding ceases in September, since the parent generation is rapidly dying off by October and completely so by November. The young generation comes into population from June and predominates in October, and extends through winter without coming into breeding condition. The life span of the vole may be more or less than 1.5 years. Pregnant females were obtained from May to November. The maximum monthly pregnancy rate occurred in June. The average number of embryos was 3.5. The monthly average testicle size increases and generally shows a maximum after winter. The testicle size was quickly reduced in September.