Dogs are generally pretty good at going green. If you think about it, they don't use more than they need, provide their waste as fertilizer, and are generally happy just hanging out. Their fur has adapted to keep them the right temperature in the right climate, and they eat whatever food is locally available.
Urbanized dogs have it a little tougher, as they have to "curb their waste" and get their food from the pet store. Apparently some dogs in Moscow have realized that their carbon footprints are getting a little out of hand and have turned to mass transit to help reduce their environmental impact.
Check out the article.