The chapter on parental behavior in the new textbook Ethology: Mechanisms, Ontogeny, Function, and Evolution of Animal Behavior discusses the fundamental principles of parental investment in offspring. It presents the current perspective on this unique type of altruistic behavior. The chapter defines basic concepts and terminology, describes parental and offspring strategies and conflicts, and outlines various forms and styles of parental care. It delves into topics such as nursing and weaning, using the example of the domestic horse to illustrate the reproductive and parental cycle of mammalian females. The chapter also examines typical cases of parental function failure, including instances of parental abandonment, parental cannibalism, and male infanticide, as well as caring for non-biological offspring.