Susan Butcher holds her dog, Tolstoy Butcher, as they get ready for the Iditarod Trail Sled Dog Race that starts Saturday in Anchorage, Alaska. Butcher is the defending champion of the 1,049-mile grueling event, which she has won four times. Her main challenger is Rick Swenson, who also has won four times in what has become the Super Bowl of sled-dog racing. Seventy-three dog teams will be competing this year on a trail that is slush by day and ice by night.