Female Incitation of Male Competition: A Mechanism in Sexual Selection

Abstract

Females that mate with the most fit male available leave more viable offspring than females that mate with males of lesser fitness. We describe a mechanism by which females facilitate mating with a superior genotype, as reflected by age, social rank, and sexual experience, without exerting choice. Female elephant seals increase the probability of mating with a mature, high-ranking male by simply rejecting all copulatory attempts during early estrus. Females protest loudly when mounted; this signals all nearby males and activates the dominance hierarchy. The probability that the mounting male will be interrupted by another male is a function of the mounter's social rank. The lower his rank, the higher the probability of interruption. The result is that mature males of high social rank have more time and freedom to attempt copulation, and they succeed in doing most of the mating. The behavior of the female intensifies this monopoly by making it more difficult for young, subordinate males to copulate. A similar female strategy seems to operate in several species where the female is courted by several males. Influencing the genotype of her offspring is an important means by which a female can increase her inclusive fitness. This aspect of sexual selection has been neglected.