Abstract and Summary

In Norway rats (Rattus norvegicus) postpartum copulation began later, and was more rapid than mating during a cycling estrus. Faster postpartum mating was a result of shorter intervals between intromissions, rather than fewer intromissions. In addition, postpartum pairs showed a trend towards fewer ejaculatory series. Postpartum female sexual initiation and her attractiveness to the male produced rapid postpartum mating. Preliminary evidence indicates that pups' presence does not determine faster postpartum mating, yet postpartum females did exhibit time-sharing relationships between their mating and maternal demands. We hypothesize that the rapid pace of postpartum mating is produced by intrinsic neuroendocrine changes characteristic of postpartum estrus and possibly by sexual experience.