Maurice Hornocker is recognized worldwide as the first scientist to unravel the secrets of America's most enigmatic predator—the mountain lion. A story of redemption, this book is a memoir about the never-before-told adventures, challenges, and controversies surrounding Hornocker’s groundbreaking study of cougars in the remote reaches of the Idaho Primitive Area. North America's biggest cat was once killed for bounty dollars, slaughtered with impunity and driven toward extinction. But today's cat of intrigue, despite our lingering fears and misconceptions, has returned to much of its native range in the western United States and gained respect as a predator integral and necessary to wild ecosystems. This turnaround was triggered by one man: Maurice Hornocker. Cougars on the Cliff recounts the early years of his research (1964–1973) when he tracked lions following a dog’s nose and footprints in the snow—before telemetry was available. Hornocker was first to learn that mountain lions living in stable populations limit their own numbers through territoriality and a concept he called “mutual avoidance.” This insight flew in the face of long-held beliefs that cougars were prolific and wanton killers that needed to be controlled as vermin. Thanks to Hornocker’s work, today cougars can be found throughout the West and have even started to reclaim their place in New England.