Effect of the Presence of a Male on the Sexual Maturation of Female Mice

Three experiments were designed to examine the influence of an adult male on the rate of sexual maturation of female albino mice. Small groups of immature female mice were exposed to: 1) an adult male at various ages after weaning, 2) either an adult male or an adult female after weaning, and 3) an adult male either for 20 days before weaning or for 20 days after weaning. In each case control groups of immature females were raised in the absence of an adult. Female maturation as measured by age at vaginal opening, first vaginal estrus and first mating was accelerated in proportion to the length of exposure to an adult male. Exposure to an adult female advanced first estrus considerably less than did exposure to an adult male. Both preand post-weaning exposure to an adult male accelerated first estrus; however, post-weaning exposure was somewhat more effective. Accelerated sexual maturation was not accompanied by a more rapid increase in body weight. (Endocrinology 81: 345, 1967)