Although initially lagging behind discoveries being made in other taxa, mammalian sperm competition is now a productive and advancing field of research. Sperm competition in mammals is not merely a ‘sprint-race’ between the gametes of rival males, but rather a race over hurdles; those hurdles being the anatomical and physiological barriers provided by the female reproductive tract, as well as the egg and its vestments. With this in mind, in this review, I discuss progress in the field while focusing on the female perspective. I highlight ways by which sperm competition can have positive effects on female reproductive success and discuss how competitive outcomes are not only owing to dynamics between the ejaculates of rival males, but also attributable to mechanisms by which female mammals bias paternity toward favourable sires. Drawing on examples across different species—from mice to humans—I provide an overview of the accumulated evidence which firmly establishes that sperm competition is a key selective force in the evolution of male traits and detail how females can respond to increased sperm competitiveness with increased egg resistance to fertilization. I also discuss evidence for facultative responses to the sperm competition environment observed within mammal species. Overall, this review identifies shortcomings in our understanding of the specific mechanisms by which female mammals ‘select’ sperm. More generally, this review demonstrates how, moving forward, mammals will continue to be effective animal models for studying both evolutionary and facultative responses to sperm competition.

This article is part of the theme issue ‘Fifty years of sperm competition’.

虽然最初落后于其他分类群的发现，但哺乳动物精子竞争现在是一个富有成效和进步的研究领域。哺乳动物的精子竞争不仅仅是雄性雄性配子之间的“短跑竞赛”，而是跨越障碍的竞赛；这些障碍是由女性生殖道以及卵子及其外衣提供的解剖学和生理学障碍。考虑到这一点，在这篇评论中，我讨论了该领域的进展，同时关注女性的视角。我强调了精子竞争对雌性生殖成功产生积极影响的方式，并讨论了竞争结果如何不仅归因于竞争雄性的射精之间的动态，而且归因于雌性哺乳动物将父权偏向于有利的父亲的机制。借鉴不同物种（从小鼠到人类）的例子，我概述了积累的证据，这些证据坚定地证明精子竞争是男性特征进化中的关键选择力量，并详细说明女性如何应对随着卵子增加而增加的精子竞争力对受精的抵抗力。我还讨论了在哺乳动物物种中观察到的对精子竞争环境的兼性反应的证据。总的来说，这篇综述指出了我们对雌性哺乳动物“选择”精子的具体机制的理解存在缺陷。更一般地说，这篇综述展示了哺乳动物将如何继续成为研究精子竞争的进化和兼性反应的有效动物模型。

本文是“精子竞赛五十年”主题刊的一部分。