Spend today or build for tomorrow? Kinship dynamics and the evolution of alternative helping strategies in cooperative breeders

Cooperatively breeding animal groups are characterised by the presence of helpers, which assist breeders in raising offspring through a variety of behaviours, such as provisioning young or defence against predators. While these systems have been studied to investigate how costly forms of help can evolve, there is little theory explaining the considerable variation in helping strategies observed across such societies. Here, we use mathematical models to investigate the evolution of alternative helping strategies. Helpers in our models can allocate effort to immediate, short-term benefits or durable, long-term benefits. We find that allocation depends on the kinship dynamics within the group. Specifically, where helpers are more related to future breeders than current breeders, often because they themselves become the future breeder, our model typically predicts greater allocation to durable help. Conversely, immediate help is favoured when helpers are less related to future breeders than to current breeders. We use our model to explore how demographic features impact kinship dynamics within the group, identify which factors select for immediate versus durable help, and which amplify conflict between breeders and helpers over helping strategies. The model is a first step towards explaining variation in types of help observed among cooperatively breeding societies.