Sedivore: The Untittled
This is the skill to live off the land and not die when you do not have the benefit of standard living conditions. I would say without the use of a city, but that is not accurate. This skill would cover a city based homeless person as well as the camper in the woods. The key here is that you do not have the normal support systems. Things covered likely included weather prediction and precautions, how to set up camp, what is likely to kill you if you eat it, how to get food, etc.