After 146 years of putting on "The Greatest Show on Earth," Ringling Bros. and Barnum & Bailey Circus will shut down in May. The decision was announced Saturday night on the circus website and cited a variety of factors including changing public tastes, high operating costs, declining ticket sales, and lengthy legal battles with animal rights activists. The circus retired its performing elephants last year in response to public and legal pressure only to see attendance plummet once the iconic show animals were gone.