"Whale ho! Thar she blows!" Decades of commercial whaling nearly decimated a variety of species of whales. These intriguing animals, which capture humans' imagination, are a keystone species. They and other keystone species are indicators of the overall health of Earth's habitats. While whales have made a comeback through an international ban on commercial whaling, they are still threatened with extinction. In fact, two whale species--the Cook Inlet beluga whale and the Southern Resident killer whale--are endangered. Global warming, water and noise pollution, and commercial shipping and fishing are among the most serious threats to whale survival.Meet the scientists, citizen scientists, researchers, whale watching guides, their crews, and other concerned citizens who are working together to protect whale populations around the globe. Learn about whale biology, habitats, and behavior, and discover more about the high-technology tools and apps that help researchers in their work. Discover whales in pop culture, from Moby Dick to Kilikum, the popular SeaWorld orca and star of Blackfish, an in-depth documentary film about whales in captivity. And find out how you, too, can join the effort to protect Earth's largest mammals.