This study investigated the effect of predation induced stress during pregnancy on demasculinization of sexual behavior for male offspring in root voles Microtus oeconomus . Male offspring were randomly assigned to four groups. Two groups were stressed by predation and restricted food, respectively, in the prenatal period. One group was stressed by predation after weaning. The remaining was the control group. During adulthood, male offspring were tested for sexual behavior and anogential distance. The results showed that prenatal stress with predation induced a major impairment of male sexual behavior and anogential distance. The group with restricted food displayed a minor impairment in male sexual behavior and anogential distance. The weaning stress showed no marked differences in male sexual behavior and anogential distance when compared to controls. These results demonstrated that predation induced prenatal stress, together with the stress with restricted food in the mothers induced the behavioral and the morphological demasculinization of their male offspring. The effect of demasculinization occurred only during the critical phase that caused sexual differentiation of the male embryonic hypothalamus.
