An abundance of evidence points to the survival of the grizzly bear in Colorado's San Juan mountains; but try as he might, Petersen, a seasoned outdoorsman and nature writer, can produce neither hide nor verified hair of his quarry. Until a harrowing encounter in 1979, when an outfitter stabbed a female grizzly to death with an arrow, the last confirmed grizzly bear in the state of Colorado was thought to have been killed by a government trapper in 1951. Since 1979, a wealth of circumstantial evidence, in the form of hair and scat samples, photographs and eyewitness accounts, has created a hard-core cadre of believers in the existence of a small number of wary grizzly bears inhabiting high, remote regions of the San Juans. Petersen, a congenial writer, interviews a convincing and colorful array of outdoorsmen, ranchers, federal and state wildlife and forest managers and biologists and treks to mountainous venues to investigate purported sightings and spoor of ursus horribilis. Whether these bears do exist is never definitively resolved, and while Petersen's writing is often suspenseful, that element eventually wanes as it becomes clear that the grizzly's elusiveness extends to these pages as well. Petersen never retreats, exactly, from his conviction that recent evidence points to the grizzly's precarious survival, but he does allow that the black bear, a widespread inhabitant of the region, frequently exhibits many of the characteristics of its larger and fiercer cousin, and accounts for many of the conflicting opinions on the existence of the grizzly. Still, much is to be learned here. Chapters on Glacier and Yellowstone Park grizzlies, for instance, provide a good comparative basis for understanding the habits of any remaining Colorado bears, including the problems of bear-human encounters. Whether read as outdoor adventure, ecological science, or detective story, this is a well-documented and usually lively addition to recent wildlife literature.