Reconceives whale songs as a sophisticated sonar system, revealing incredible insights into these creatures' intelligence and behavior. With breathtaking complexity and haunting beauty, the songs of whales have long fascinated scientists. Whales are the only mammals that sing continuously for ten hours or more, and they do so loudly, even when no listeners are nearby. They also change the songs they sing every year. In Why Whales Sing, bioacoustician and cognitive scientist Eduardo Mercado transforms our understanding of these enigmatic sounds and proposes a groundbreaking theory that challenges decades of established science. Fifty years of field research have led most scientists to conclude that humpback whales sing for the same reason that birds do: to advertise their sexual fitness. But if whale songs are nothing more than tools of attraction, why do whales sing even when they're alone? In light of modern advances in neuroscience and ocean acoustics, Mercado reaches the surprising conclusion that whales may not actually be "singing," but rather engaging in an activity more commonly associated with dolphins and bats—echolocating—which enables them to see their world with sound. By incessantly streaming sounds while listening closely to the returning echoes, whales may be actively tuning their brains in ways that allow them to monitor the movements of silent whales located miles away. Sophisticated, long-range sonar can enable whales to perceive their vast underwater worlds in unimaginable ways. From the military origins of whale song recordings to the persistent mysteries of cetacean communication, this book displays the wonder of whales and reshapes how we view their intelligence, behavior, and acoustic mastery.