Young couple goes on van tour of US, boy comes back with van - no girl

He's been "missing" for about a month now. How long could he exist in the swamp on his own, drinking swamp water, eating bugs and berries? In my mind there are two possiblities....He's dead (probably lunch for a gator) or he is not in the swamp but living relatively comfortable either in a more hospitable part of the country or holed up in a hideout somewhere (camp, boat, etc.).