The review by T. H. Clutton-Brock explores the diverse mating systems in mammals, contrasting them with those of birds. In mammals, over 90% of species exhibit polygynous or monogamous mating patterns, unlike birds where most species are monogamous. The study highlights four main forms of mate guarding: defending individual females, feeding territories overlapping female ranges, defending specific groups of females, and defending dispersed or clustered mating territories. Female mating behavior includes long-term monogamy, serial monogamy, polyandry, and promiscuity. Clutton-Brock argues that variation in male mating behavior is influenced by four key factors: the extent to which male assistance in rearing offspring increases female reproductive success, the size and stability of female ranges and groups, and the density and distribution of females. These factors help explain the evolution of different mating systems, such as monogamy and lek breeding. The review also discusses various mating systems, including obligate monogamy, facultative monogamy/polygyny, unimale groups with spatial defense, multimale groups with spatial defense, unimale groups without spatial defense, multimale groups without spatial defense, and mating territories. Each system is described in detail, with examples from different mammalian species, and the evolutionary and ecological implications of these systems are discussed. The study emphasizes the importance of understanding the functional significance of social and reproductive behavior in mammals.The review by T. H. Clutton-Brock explores the diverse mating systems in mammals, contrasting them with those of birds. In mammals, over 90% of species exhibit polygynous or monogamous mating patterns, unlike birds where most species are monogamous. The study highlights four main forms of mate guarding: defending individual females, feeding territories overlapping female ranges, defending specific groups of females, and defending dispersed or clustered mating territories. Female mating behavior includes long-term monogamy, serial monogamy, polyandry, and promiscuity. Clutton-Brock argues that variation in male mating behavior is influenced by four key factors: the extent to which male assistance in rearing offspring increases female reproductive success, the size and stability of female ranges and groups, and the density and distribution of females. These factors help explain the evolution of different mating systems, such as monogamy and lek breeding. The review also discusses various mating systems, including obligate monogamy, facultative monogamy/polygyny, unimale groups with spatial defense, multimale groups with spatial defense, unimale groups without spatial defense, multimale groups without spatial defense, and mating territories. Each system is described in detail, with examples from different mammalian species, and the evolutionary and ecological implications of these systems are discussed. The study emphasizes the importance of understanding the functional significance of social and reproductive behavior in mammals.