"So can a great dane / chihuahua mix survive?"
Actually, yes, they can.
If you let dogs roam the planet as they may, in a matter of years we would haev "true dog" again. And again, in a matterof years, one could breed them by their atributes/abilities to fit the needs of their area.
Yorkshire terriers and poodles did not roam the earth as wild animals. They were bred into existance by a guiding hand. A hand with foresight and intellegence.
"Actually, yes, they can.
If you let dogs roam the planet as they may, in a matter of years we would haev "true dog" again."
Sorry I can't bear but ask...
have you proven this in the lab