Traps. Fences. Poison. Ranchers have tried everything to keep predators from their livestock. But guard llamas? At Thirteen Mile Ranch near Belgrade, Mont., llamas have kept watch over the sheep for a decade. The result: No losses from coyotes - the bane of sheep ranchers. "Our llamas have developed some kind of an understanding with a local and fairly stable coyote pack," says Becky Weed, who runs the ranch with her partner, David Tyler. "They know the ropes, and we know the ropes, and I think they understand that we don't bother them. We like to have them around because...