Mammalian sociobiology is a rapidly advancing field which has made enormous strides in the last ten years. The last major monograph on the subject (Ewer, 1968) was published sixteen years ago, and there is a need for this information to be examined in terms of modern sociobiological theory. My approach throughout is evolutionary and is therefore directed strongly towards research which throws light on the ways in which mammals behave in their natural environments. I have tried to cover as wide a range of mammalian species as possible, although, in some cases, the only data available were obtained from captive individuals. The coverage of this book is not a reflection of the volume of literature published on different species, as I have tried to avoid undue emphasis on the social behaviour of primates and laboratory rodents. I have made scrupulous efforts throughout to avoid an anthropomorphic approach to mammalian behaviour. Terms such as 'strategy', 'evaluation' or 'choice' do not therefore imply conscious planning, but are used neutrally in the way in which they would be applied to a chess-playing computer. In the case of mammals, the programmer was natural selection. While I am fully aware that human beings are mammals, any detailed consideration of human social behaviour lies outside the scope of this book. However, the book may provide a complementary text to those interested in that subject.