As the dusty truck loaded with guns and radio gear rolls down the Arizona highway south toward Nogales and the Mexican border, Bernell E. ("Bernie") Lawrence points toward a range of mountains. "O.K.," he drawls in a desert-dry voice, "where's the place up there you'd look for lion tracks?" He already knows. "Lions like the backbone of a set of mountains. They'll cross where two canyons meet. For them it's like climbing stairs." Lawrence is 48. For much of his life he tracked and killed mountain lions, bears and coyotes. Then society's shifting values made it less trouble to hunt men.
His...