亜高山森林帯におけるヒメヒミズおよびトガリネズミの体重組成および繁殖活動(本州八ヶ岳のネズミおよび食虫類-4-) Small Mammals of Mt. Yatsugatake in Honshu. IV. : Seasonal Differences in Body Weight and Reproduction of Dymecodon pilirostris and Sorex shinto in the Subalpine Forest Zone on Mt. Yatsugatake.
The authors certified that five species of insectivora inhabit the subalpine forest zone (alt. 1,800-2,400m) of Mt. Yatsugatake. They are Euroscaptor mizura, Urotrichus talpoides, Dymecodon pilirostris, Sorex shinto and Chimarrogale platycephala. From April, 1962 to March, 1964, the authors collected small mammals monthly by snap traps in the subalpine forest zone on Mt. Yatsugatake in Honshu. The total number of captured mice and voles was 1,577. The number of moles and shrews taken was 387 with the following breakdown: Urotrichus talpoides 25, Dymecodon pilirostris 257, Sorex shinto 105. It was noted that larger number of Dymecodon pilirostris and Sorex shinto appeared in June and in winter. Pregnant females were found in May (2 specimens) in Urotrichus talpoides, in May (3) and July (3) in Dymecodon pilirostris, in May (2) and June (5) in Sorex shinto. The average embryo sizes of each species were as follows: Urotrichus talpoides 4.5, Dymecodon pilirostris 3.7, Sorex shinto 3.8. Mammal formula of each species examined are shown in Table 3. The monthly average testicle sizes advance rapidly to the maximum after winter in Dymecodon pilirostris and Sorex shinto, but after which their size are quickly reduced. In Dymecodon pilirostris and Sorex shinto, from the frequency distribution table of body weight, the following tendencies are noted: wintered animals grow repidly and reach maturity from April to July. But breeding ceases in August mainly because the parent generation is rapidly dying off by October, completely so by November. Young come into the populations from August onwards, predominating from August and overwinter without coming into breeding conditions. The life span of these species is supposed to be about 1-1.5 years.
動物学雑誌 74(3), 76-81, 1965-03