Effects of the male on growth, sexual maturation, and ovulation of young female meadow voles, Microtus pennsylvanicus

Abstract

Laboratory bred female meadow voles were exposed for 21 days, from weaning at 18 ± 1 days of age, either to mature males (with or without physical contact), females (virgin or multiparous), male urine, or empty cages to assess the influences of the social environment on growth, rate of sexual maturation and ovarian function. When allowed direct physical contact with males for 2 h each day the females showed no significant weight gain but an acceleration of sexual development compared with controls was observed. Those exposed to males or male urine through a wire barrier for 24 h each day demonstrated increase in weight gain and rate of sexual development compared to controls and females exposed to females. One female, exposed to a male through a wire barrier, had corpora lutea in her ovaries when she was killed. Under the experimental conditions female conspecifics had no effect on growth or the attainment of sexual maturity. Mediation of the male influence is concluded to be pheromonal with the active compound(s) present in the urine.