Dog owners in Brunete, Spain don't pick up after their dogs. Advertising firm concocted a nudge. Send the poop back to the owners. Volunteer chats up the owner and finds out dog's name. Matchting owner and address from database. He scoops up the poop, places it in package marked 'Lost Property' to send to owner. 147 deliveries were made resulting in 70% decline in dog droppings littering the streets.