I've seen a duo of rat hunters out with dogs in the DuPont circle area. It's two guys with headlamps and hockey goalie sticks and each guy has a dog on a leash. They seem to have retriever looking puppies that they are using(wouldn't be my first choice) but I've seen them out quite regularly for at least the last year. They are hard to miss. It seems they are doing it for sport and not connected to any city rat clean up.