Believe it or not, dogs produce more carbon footprint than SUVs. Specifically, a medium-sized dog produces more carbon footprint than a Toyota Land Cruiser. The amount of carbon footprint for a dog is determined by how much it eats. Due to eating a lot of meat, dogs (and cats) have such high carbon footprints. A cat can have a carbon footprint equivalent to a small Volkswagen.

Source: http://www.ecoworld.com/animals/dogs-pollute-more-than-suvs.html