Higher sociability leads to lower reproductive success in female kangaroos

In social mammals, social integration is generally assumed to improve females’ reproductive success. Most species demonstrating this relationship exhibit complex forms of social bonds and interactions. However, female eastern grey kangaroos (Macropus giganteus) exhibit social preferences, yet do not appear to cooperate directly. It is unclear what the fitness consequences of sociability could be in species that do not exhibit obvious forms of cooperation. Using four years of life history, spatial, and social data from a wild population of approximately 200 individually recognizable female eastern grey kangaroos, we tested whether higher levels of sociability are associated with greater reproductive success. Contrary to expectations, we found that the size of a female’s social network, her numbers of preferential associations with other females, and her group sizes all negatively influenced her reproductive success. These factors influenced the survival of dependent young that had left t...