Taking an integrated approach to the biology of marine carnivores, cetaceans, and sirenians, twenty-two prominent researchers compare marine mammals with one another and with terrestrial mammals, providing a framework for fundamental biological and ecological concepts. They describe functional morphology, sensory systems, energetics, reproduction, communication and cognition, behavior, distribution, population biology, and feeding ecology. They also detail the physiological adaptations--for such activities and processes as diving, thermo-regulation, osmoregulation, and orientation--that enable marine mammals to exploit their aquatic environment.