Reproductive benefits from female promiscuous mating in a small mammal

Promiscuous systems where both males and females mate several times with di fferent individuals are widespread among mammalian species. As a consequenc e, females obtain sperm from more than one male and paternity is decided by sperm competition. In theory, females might gain 'genetic benefits' for th eir offspring from this mechanism. In a mating experiment we now demonstrat e in the promiscuous rodent Galea musteloides that females which were paire d with four males, and became pregnant, weaned more surviving offspring tha n females which were paired with a single male. Litter sizes did not differ between the two groups. The data support the hypothesis that promiscuous f emales copulate with several males to induce sperm competition and/or to en force cryptic female choice and thereby increase the viability of their off spring.