it isn't really considered a skills, it is kind of in the air surrounding you. For example i didn't take nor toothpaste nor toothbrush - it isn't an omission nor i'm anti-hygienic - instead i used small fir sticks to chew and to pick between and clean the teeth - the resin has mild anti-microbial properties and have that nice smell. Such possibility was mentioned to me once by a friend, one of the strongest mathematicians in our year, a city dweller, when we were taking a walk around campus (if memory serves me right it was in the context of discussing such a practice in some region(s) in India where a local plant is used for that purpose ).

It is somewhat puzzling and sad that despite large territory and amazingly rich Nature, there is such a profound separation from Nature in US. Almost all the land is private, and even if not it is still mostly fenced with limited access and permits for everything (and naturally the very few available places are overcrowded because of such a [pretty artificial] scarcity). Limited access to land also naturally affects access to water bodies. You can't just come to a body of water and say go for swim if water is clean, like you'd do say in Russia. From US land rights system POV even the Nordic private property system with "right to roam" looks like communism :)