Interactions of Contact, Odor Cues, and Androgens in Strange-Male–Induced Early Pregnancy Disruptions in Mice (Mus musculus )

Novel males can disrupt early pregnancy in female house mice (Mus musculus). In Experiment 1, exposure to novel males disrupted pregnancy, but exposure to male urine did not. In Experiment 2, urine from male or female mice or rats painted on females' noses did not influence pregnancy. In Experiment 3, the conjunction of urine painted on female's noses and vulval stimulation did not affect pregnancy more than water with similar stimulation. In Experiment 4, males housed above females were separated from them by a wire mesh grid; intact males disrupted pregnancy, but castrated ones did not. In Experiment 5, such housing of castrated males or ovariectomized females produced a strong disruption of pregnancy if the stimulus animal was given testosterone but not if it was given oil injections. In Experiment 6, transfers of odorous emissions failed to disrupt pregnancy. Contact and androgen activity are necessary for strange males to disrupt pregnancy.