Reproductive Skew In Female-Dominated Mammalian Societies

We review available data documenting reproductive skew in the small group of mammals characterized by female dominance over males, focusing mainly on lemurs and spotted hyenas (Crocuta crocuta). Although most females in all lemur species examined here appear to bear young at each opportunity, we know very little about variation in longer-term reproductive success or rates of reproduction among female lemurs. Therefore we cannot draw firm conclusions in regard to reproductive skew among female lemurs except that at present this appears to be slight. However, current data show that female lemurs typically mate with multiple males, and that a substantial fraction of litters containing multiple offspring is sired by more than one male. The extent of reproductive skew in male lemurs varies among species, but there is a slight trend, among the lemur species for which genetic data exist, for male skew to decrease as the intensity of female dominance increases. Variance in reproductive success among female spotted hyenas appears to be substantially greater than it is in male-dominated species in which plural breeding occurs. In this species, female dominance, combined with virilization of the external genitalia, may increase female control over mating to its extreme limit, such that we find very little reproductive skew among males relative to that found in other polygynous mammals. The most dominant male hyenas often achieve very little reproductive success. Overall, reproductive skew among females in female-dominated mammals appears to be the same as or slightly greater than that in male-dominated species, whereas skew among males in female-dominated species generally tends to be relatively low.