On a brisk October afternoon, Ruin — a 15-month-old Dutch Shepherd mix puppy with a dark brindle coat and one floppy ear — takes a break from an obstacle course and perches on a red wooden box inside a barn in Livingston, Montana. His head sinks into the crook of a Svalinn trainer's arm, as the trainer deems Ruin one of his favorites. Two hours later, the trainer — now in a foam Michelin-man neck-to-heel suit — crouches near the box, imitating a quiet intruder. He cracks a whip onto a rubber