The dude is traveling deep into the jungles of South America (where there are no Wal-Marts nearby) and only carries ONE knife? Geez!
I usually have at least four knives when I go blue-gill/bass fishing: different purposes + a spare.
That wasn't a knife -
http://the-illuminati.net/wp-content/uploads/2012/06/1c656__crocodile- dundee-knife.jpg
Now thats a Knife. Or at least one I'd bring into the Jungle.
Nolan Haters - http://24.media.tumblr.com/tumblr_mbtzjoCeTG1qzp0kuo1_1280.gif
He probably reasoned that since his knife was all he needed for protection in the urban jungle it would be all he needed for protection in the tropical jungle as well. He didn't realize that he was a fish out of water.