He slowly starved because he ate a plant that poisoned him and made it impossible for him to digest food.
He was trapped by a rising river and therefore could not get out to get the help he needed.
Pretty crummy way to die, eh?
But he had plenty food, he just could not digest it.
He ate those berries that looked like the edible type....whoops!! But anyway you look at it,
his inexperience got him killed.But you would still have to think there was a way out. If the bus made it out there
you would think there was bridge somewhere.
(My bold)
The movie must shortcut the info in the book, I haven't seen the movie. McCandless correctly IDed an edible wild potato-like tuber, the book said the tubers were edible, in season (but they become hard & indigestible out of season). There is also a closely related plant that looks v. much like the potato-like plant. The field guide McCandless had didn't mention that the seeds of the lookalike are slow poison - incidents of such poisoning are v. rare, because you have to ingest a lot of it. The author of
Into the wild thinks that McCandless switched from the increasingly inedible tubers, incorrectly IDed the lookalike, switched to eating the seeds, ate a lot, & the poison persists in the body.
To flush the poison from the system, you need a lot of protein & fats - McCandless was losing weight all the time he was out there in AK - the poison meant he would have had to have eaten prodigious amounts of food (& stopped eating the poisonous seeds), & he just couldn't gather that much food. He may have understood he was eating the wrong plant, there @ the end. Too late to do anything about it.
The author points out - winter in AK is when it's easiest to travel, physically. (The rivers, swamps, etc. freeze - like a highway. But food is a problem then.) There was no bridge, someone dragged 3 old buses in as hunting shelters. The other 2 were gone.