Life History of Small Mammals in Fallow Fields

5. Reproduction in the Large Japanese Field Mouse and the Feral House Mouse

Abstract

Reproduction status was compared between large Japanese field mouse (Apodemus specious) and house mouse (Mus musculus molossinus), which were predominant on fallow fields in Nagoya City (35°03'N, 135°57'E, alt. 5 to 20 m) . The main breeding season in the field mice was spring (March to May) and fall (September to December) . Although the house mice were not trapped on May to October, it may be considered that they bred on October to May to say the least, and were able to breed throughout the year. The house mice had a significantly larger mean number of normal embryos per litter than the field mice (6.0 versus 4.6) . The field mice had the significantly smaller number of embryos in spring than in fall (3.2 versus 5.6), whereas the house mice did not show significantly differences between the spring and winter ones (5.3 versus 6.2) . It may be concluded that the house mice, as compared to the field mice, have the higher reproductive capacity, in the respects of their longer breeding season and larger embryo sizes.