Into The Wild | Our South American Animals Part 1 (Iguana, Chinchilla, Tarantulas) 

I watched a pretty cool documentary about green iguanas. One of their major predators as babies are actually basiliks

I saw a video of a Ocelot taking down and killing an fully grown Green Iguana. You mention that Jaguars, Caimans and Anacondas are the only big predators in South America, well down forget the Puma, a fairly large predator and I wouldn’t be surprise if they too hunt very large Iguanas.