Why Do Cuckolded Males Provide Paternal Care?

A comparative analysis across insects, birds, fish, and mammals reveals why it sometimes pays for males to care for the offspring of other males. In most species, males do not abandon offspring or reduce paternal care when they are cuckolded by other males. This apparent lack of adjustment of paternal investment with the likelihood of paternity presents a potential challenge to our understanding of what drives selection for paternal care. In a comparative analysis across birds, fish, mammals, and insects we identify key factors that explain why cuckolded males in many species do not reduce paternal care. Specifically, we show that cuckolded males only reduce paternal investment if both the costs of caring are relatively high and there is a high risk of cuckoldry. Under these circumstances, selection is expected to favour males that reduce paternal effort in response to cuckoldry. In many species, however, these conditions are not satisfied and tolerant males have outcompeted males that abandon young. Author Summary: In most species where it has been studied, males do not abandon or reduce paternal care when they are cuckolded by other males. These observations have presented a long-standing challenge to our understanding of what drives selection for paternal care. Our analysis of cuckolded fathers from 50 species of birds, fish, mammals, and insects, however, shows that sometimes it pays for males to stick around. In the case of humans and burying beetles, this is because females are relatively monogamous—by deserting, it is most likely the case that fathers will be deserting their own young. In species such as the chacma baboon, males face a significant risk of cuckoldry, and face potentially high penalties in terms of future breeding success by wasting precious resources on the young of other males. Unlike in humans, promiscuous females in these species will almost certainly lose the support of her mate in the effort to raise her young to adulthood.