A comprehensive scientific study of the behavior of Hawaiian spinner dolphins both in the wild and captivity--and of the dangers posed to dolphins by the tuna-fishing industry. Norris, retired professor of natural history at U. Cal. at Santa Cruz, has spent the better part of 30 years investigating marine mammals; he devotes the first half of this study to his findings on spinner dolphins. Through long-term observations of dolphin behavior (much of it done below water in a leaky homemade craft), Norris and his associates unlocked many of the secrets of dolphin life, including why they swim in organized schools and use sonarlike echolocation (to protect themselves from predators), and why they make clicking sounds (to stay in close communication and to capture prey). The book's second half concentrates on Norris's work to help protect marine mammals. He was instrumental in getting 1972's Marine Mammal Welfare Act passed, and he's worked to find alternative fishing methods to help keep dolphins from being killed in tuna nets. His firsthand research on tuna boats, spent observing fishing methods and the behavior of trapped dolphins, led to a great reduction--but not elimination--of unnecessary dolphin deaths. With a heavy scientific slant, of greatest appeal to those concerned with the welfare of dolphins and other marine animals.