Why Male Mammals Are Monogamous

Abstract

Monogamy has long fascinated scientists and the general public alike (1). Its occurrence in fellow mammalian species has puzzled evolutionary biologists (2–4). Male mammals have a much higher potential for producing offspring per unit time than females, making it necessary to identify selective advantages that would more than compensate for the loss of potential reproduction suffered by males that confine their reproductive activities to a single female. On page 526 of this issue, Lukas and Clutton-Brock (5) show that the costs of monogamy for males are not compensated by fitness benefits through paternal care. Instead, by forming pairs, males overcome disadvantages that arise because ecological factors promote wide spacing of individual females.