Parenting and potency: alternative routes to reproductive success in male Mongolian gerbils

Adult male Mongolian gerbils, Meriones unguiculatusgestated in intrauterine positions between two female fetuses (2F males) are less likely than are adult males gestated between two male fetuses (2M males) to impregnate strange female gerbils with whom they are paired. The reduced copulatory success of 2F males is correlated with both lower circulating levels of and reduced sensitivity to testosterone. We asked whether 2F male gerbils …