Book excerpt: The study of alternative reproductive tactics (the behavioural strategies used by individuals to increase their reproductive success) is an evolutionary puzzle, and one of great interest to researchers. For instance, why do some males guard both nest and eggs, while others sneak into nests while pairs are spawning and fertilise those eggs? The field offers a special opportunity to study the evolution and functional causes of phenotypic variation, which is a general problem in the field of evolutionary biology. By integrating both mechanistic (psychological) and evolutionary (behavioural ecology) perspectives and by covering a great diversity of species, Alternative Reproductive Tactics addresses this integrated topic of longstanding interest, bringing together a multitude of otherwise scattered information in an accessible form that is ideal for graduate students and researchers.