Litter Size and Vaginal Smear in Microtus montebelli

Abstract

To be able to reproduce the vole (Microtus montebelli) intentionally, the authors observed litter sizes and vaginal smears of female voles under the different social conditions (isolated, adjacent to a male, lived in a same cage with a male) . 1) There was little influence of the inbreeding (4 generations) and the seasons on litter sizes. Therefore, it seemed that the vole was able to reproduce throughout the year under the room condition (20-25°C) . 2) From the presence of cornified cells in the smears at copulation and with PMS treatment, these cells seemed to be an index of estrous in the female vole. 3) In the isolated feeding, leucocytes and nucleated cells were predominantly observed in the smears. Regardless of the presence of these cells, females showing a recurrent appearance of cornified cells were found in half the number (5/10 heads) . When females were lived in a same cage with males (1: 1), the recurrent females showed the same appearence rate as that of isolated feeding (13/24 heads) . Thus, the vaginal smear in the vole did not show a definite pattern by reason of individual difference.