Stud males and dud males: intra-uterine position effects on the reproductive success of male gerbils

Sexually mature male Mongolian gerbils, Meriones unguiculatus, from known intra-uterine positions were each paired with a succession of nulliparous females. Those males that had matured in intra-uterine positions adjacent to two males (2M males) sired an average of 28% more young than did those males that had matured in intra-uterine positions between two females (2F males). In a second experiment, female gerbils chose between pairs consisting …