There are very few places in the world where snakes do not live. And many of them are poisonous. In North America, there are a number that you need to avoid being bitten by. And if you are bitten, there are certain things you need to do. In SHTF scenarios you may be forced to deal with snakes in ways you are not normally used to. You will probably be out of touch with usual medical facilities, so if you are bitten you will have to handle it yourself.