This book series focuses on endangered mammals, including tapirs, sloths, pacas, bats, and felines. In this installment, the study shifts to two groups of aquatic mammals: cetaceans (whales, dolphins, and beaked whales) and sirenians (manatees). These mammals exclusively inhabit water environments, and their physical adaptations and behavior aid their survival. However, they face serious threats from pollution in rivers and oceans, as well as human activities such as fishing and industrial whaling.