The city of Moscow has about 35,000 stray dogs. Of that group, approximately 20 have one very surprising habit. Every day, these 20 stray dogs board the metro in the Russian suburbs and ride the rails into the city to find food. At the day's end, the dogs get back on the train and head home to the suburbs. How did they learn to get on and off at the right stops and times? It's believed that because dogs have co-evolved alongside humans for thousands of years, they can react to our emotional and physical cues. By observing humans board and get off the subway trains to go to work, these dogs are thought to have learned that there is a destination and reason for navigating the metro system.