On the function of the multiple-intromission, multiple-ejaculation copulatory patterns of rodents

Abstract

Males of many rodent species attain both multiple intromissions before ejaculating and multiple ejaculations. It is suggested that an evolved function of the multiple intromissions may be the removal of sperm, vaginal casts, copulatory plugs, and plug fragments from the female’s reproductive tract. By thus cleansing the female’s tract before ejaculating, the male can both facilitate effective deposition of the plug in the cervix and benefit from reduced sperm competition. Multiple ejaculations are interpretable in relation to pregnancy initiation and sperm competition.