Four decades ago, the areas around Yellowstone and Glacier National Parks sheltered the last few hundred surviving grizzlies in the Lower 48 states. Protected by the Endangered Species Act, their population has surged to more than 1,500, and this burgeoning number of grizzlies now collides with the increasingly populated landscape of the twenty-first-century American West. While humans and bears have long shared space, today's grizzlies navigate a shrinking amount of wilderness: cars whiz like bullets through their habitats, tourists check Facebook to pinpoint locations for a quick selfie...