Mammals originated on land. Millions of years ago, some of them adapted to life in the sea. They were the ancestors of today's sea mammals: whales, manatees, seals, otters, and more. Sea Mammals explores the origins and history of marine mammals, then looks at the many varieties that exist today, from the blue whale-the largest animal that has ever lived-to the vaquita, the world's smallest and most endangered sea mammal. It also focuses on the role of sea mammals in human life, the questions that fascinate marine mammal researchers, and the future of these creatures that share the oceans with fish and reptiles but are biologically closer to bears and elephants.
Table of Contents
Introduction: Classifying Life 7 Animal Kingdom Family Tree 16 Chapter 1 Marine Mammals of the World 19 Chapter 2 Back to the Ocean 29 Chapter 3 Cetaceans: Whales, Dolphins, and Porpoises 39 Chapter 4 Sirenians: Dugongs and Manatees 55 Chapter 5 Seals, Walruses, Sea Otters, and Polar Bears 63 Chapter 6 An Uncertain Future 77 Glossary 86 Sea Mammal Family Tree 88 Find Out More 90 Bibliography 93 Index 94