Cooperative breeding refers to a social system in which individuals other than the parents provide care for the offspring. Since individuals delay breeding and invest in the offspring of others, cooperative breeding poses a challenge to a Darwinian explanation of the evolution of social behavior. The contributors to this book explore the evolutionary, ecological, behavioral, and physiological basis of cooperative breeding in mammals. The book contains a collection of chapters by the leading researchers in the field, and it is the first book dedicated exclusively to the study of mammalian cooperative breeding.