A male gerbil's intrauterine position affects female response to his scent marks.

Female Mongolian gerbils scent marked more frequently in response to scent marks deposited by adult male conspecifics that, as fetuses, had resided in intrauterine positions between two male fetuses (2M males) than in response to scent marks deposited by adult male conspecifics that had resided in intrauterine positions between two females fetuses (2F males). Because 2M male gerbils are significantly more likely than are 2F male gerbils to impregnate females, and because female gerbils are able to discriminate among males after exposure to their scent marks, the ability of female gerbils to discriminate scent marks of 2M males from those of 2F males may serve as a basis for female identification of males likely to make suitable mates.