On a typical summer day, the waters of Johnstone Strait, in British Columbia, are abuzz with the clicks, whistles, and pulsed calls of killer whales. These animals—the summer residents of the inland waterways off northern Vancouver Island—are perhaps the most intensively studied whale population in the world. Through research based on the ability of observers to visually identify every individual in the population, scientists have put together an extensive and detailed outline of the whales' social relationships over the last three decades. And since the early 1980s, researchers have had hydrophones in the water, recording myriad hours of whale conversation.