Social Environment and Ovulation in the Vole, Microtus Agrestis

Summary. Although M. agrestis normally ovulates following coitus, virgin females in the present study ovulated when separated from a male by a single barrier of wire mesh. A smaller number ovulated when tactile contact with the male was eliminated. Changing the male behind the barrier appeared particularly effective in inducing ovulation. Control females, in the absence of males, did not ovulate. Corpora lutea resulting from the ovulations normally started to degenerate within about 3 days of their formation. Short-term changes in the vaginal smear and in sexual behaviour accompanied the ovarian changes. Direct histological evidence indicated that ovulations could be repeated once; indirect evidence (based on vaginal smears) suggested that short ovulatory cycles could occur. The significance of these results in relation to the ovulatory mechanism of the vole is discussed.