Pronghorn antelope are the fastest runners in North America, often reaching speeds of up to 100 kilometers per hour. Yet none of their current predators can run this fast. Pronghorn also gather in groups, a behaviour commonly viewed as a "safety in numbers" defence. But again, none of their living predators are fearsome enough to merit such a response. In this book, John A. Byers argues that these mystifying behaviours evolved in response to the dangerous predators with which pronghorn shared their grassland home for nearly four million years: among them fleet hyenas, lions, and cheetahs. Although these predators died out 10,000 years ago, pronghorn still behave as if they were present - as if they were living with the ghosts of predators past. This provocative hypothesis should stimulate behavioural ecologists and mammalogists to consider whether other species' adaptations are also haunted by selective pressures from predators past. The book should also find an audience among evolutionary biologists and paleontologists.