How did the elephant seal survive being driven to the brink of extinction in the nineteenth century? What variables determine the lifetime reproductive success of individual seals? How have elephant seals adapted to tolerate remarkable physiological extremes of nutrition, temperature, asphyxia, and pressure? Answering these questions and many more, this book is the result of the author's 50-year study of elephant seals. The chapters cover a broad range of topics including diving, feeding, migration and reproductive behavior, yielding fundamental information on general biological principles, the operation of natural selection, the evolution of social behavior, the formation of vocal dialects, colony development, and population changes over time. The book will be a valuable resource for graduate students and researchers of marine mammal behavior and reproductive life history as well as for amateur naturalists interested in these fascinating animals.