Family Matters: Linking Population Growth, Kin Interactions, and African Elephant Social Groups

In many species, individuals are embedded in a network of kin with whom they interact. Interactions between kin can affect survival and fertility rates and thus the life history of individuals. These interactions indirectly affect both the network of kin and the dynamics of the population. In this way, a nonlinear feedback between the kin network and individual vital rates emerges. We describe a framework for integrating these kin interactions into a matrix model by linking the individual kin network to a matrix model. We demonstrate the use of this framework for African elephant populations under varying poaching pressure. For this example, we incorporate effects of the maternal presence and matriarchal age on juvenile survival and effects of the presence of a sister on young female fecundity. We find that the feedback resulting from the interactions between family members shifts and reduces the expected kin network. The reduction in family size and structure severely reduces the positive effects of family interactions, leading to an additional decrease in population growth rate on top of the direct decrease due to the additional mortality. Our analysis provides a framework that can be applied to a wide range of social species.