The willing cuckold: optimal paternity allocation, infanticide and male reproductive strategies in mammals

Infanticide is believed to be an adaptive strategy in many mammalian taxa. A number of authors have modelled aspects of infanticide and its potential impact on social systems, but limited attention has been paid to identifying the full range of conditions under which infanticide should be favoured or the variety of potential effects that infanticide may have on male mating strategies. While most authors focus on infanticide by new male immigrants, natural selection should favour infanticide under a wider range of conditions, including sometimes by potential fathers. Here we model male decisions about whether to commit infanticide and explore how infanticide risk may affect optimal male mating strategies. Infanticide risk coupled with imperfect infanticide protection in a population creates a fitness landscape with two adaptive peaks, one representing complete paternity certainty and the other representing a compromise between maximizing paternity and minimizing infanticide risk. Which of these adaptive peaks represents the fitness-maximizing global optimum depends on a population's socioecology and characteristics of the male. In many ecological contexts, males may adaptively reduce their paternity probability to reduce the risk of infanticide. Explicit consideration of this possibility may enhance our understanding of the dynamics of mammalian intrasexual and intersexual competition in a number of ways.