Female Sneak Mating Avoids Infanticide In Golden Snub-nosed Monkeys

Sexual selection theory predicts that given differences in their reproductive costs, males and females are expected to exploit a set of alternative behavioral tactics and strategies for gaining access to mating partners and increasing individual reproductive success. In mammals that form harems, the leader males often kill unrelated and unweaned offspring to shorten the interbirth interval of the mother for the sake of reproductive opportunity. Infanticide occurs more frequently in species that a minority of males monopolized most fertile females. In the present study we investigated the effects of female sneak mating behavior on infanticide avoidance in the golden snub-nosed monkey (Rhinopithecus roxellana). Golden snub-nosed monkeys live in a multilevel society composed of several harem breeding units (OMUs) and an associated unit composed of several bachelor males (AMU or all male unit). Due to the social organization and mating system, male-male competition to fertile females would aggravate and thus may increase the infanticide risk. In this paper, we initiate combining the behavioral data and genentic data, in order to discuss the effect of female sneak mating for infanticide avoidance among golden snub-nosed monkeys. During September 2013 to June 2015, we documented extra-unit mating and affiliative behavior among a herd of wild R. roxellana by scanning sampling, focal animal sampling and all occurrence recording method. And we also collect the genetic samples of target animals via noninvasive sampling. According to the analysis results, only 31.25% of the new-born infants in 2014 were sired by the resident male of their natal OMUs. We also have made a test to compare the the genetic relationship of females & resident males with that of females & fathers in genetic/mating partners. And there was no significant difference (n= 11, P= 0.182), which show that females don't mate promiscuously for the purpose of increasing the genetic diversity. In this paper, we make comprehensive consideration to exclude other possible hypothesis. Finally, we argue that females golden snub-nosed monkeys have probably developed a sort of mechanism to avoid male infanticide efficiently by sneak mating to spread paternity estimates.