Female counter-strategies to male infanticide in primates

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Primates live in groups that show great variation in social relationships between the sexes. These relationships are influenced by male reproductive competition and female mate choice. Males sometimes use male sexual coercion of females to attain mating opportunities, and one extreme expression of male sexual coercion is infanticide by males. Infanticidal males benefit reproductively if they kill unrelated infants and they inseminate a female sooner than if they had to wait until weaning. Male infanticide has been observed in a wide range of primates, but it is now apparent that not all individuals vulnerable to infanticide are killed. This suggests that not all males are infanticidal, and/or the existence of successful male and female counter-strategies to male infanticide. Infanticide is costly for the males who sired the victims, but is even more costly for female mammals, that are more limited in their potential reproductive output. One should thus expect natural selection to favor the expression of female counter-strategies to infanticide. I will investigate the expression of female behaviors that could qualify as counter-strategies to infanticide, in situations where the infanticide risk that these females experience varies. The level of paternity certainty that resident male(s) have is inversely related to the level of infanticide risk experienced by the mothers in their group. Infanticide rate is high is the population of primates that we study, but the risk of infanticide is not distributed equally across all social conditions. Females living in uni-male groups face the least infanticide risk, as males in these groups have high paternity certainty. Females living in stable multi-male groups face a moderate level of infanticide threat, as individual males in these groups have lower paternity certainty than in uni-male groups. The risk of infanticide is most acute immediately after a takeover, as the newly-arrived males have a close-to-zero paternity certainty. I will examine if the expression of behaviors that qualify as counter-strategies against infanticide (association with a male protector, increased sexual receptivity, mating with multiple males, and rapid weaning) co-vary with the level of infanticide risk, and if they influence infant survival and female reproductive success.