He knew their anger noises, their fear noises, their food noises, their love noises.

And these noises were as definitely words in his vocabulary as are words in a human's vocabulary.
And these crocodile noises were tools of thought.

By them he weighed and judged and determined his own consequent courses of action, just like any human; or, just like any human, lazily resolved upon no course of action, but merely noted and registered a clear comprehension of something that was going on about him that did not require a correspondence of action on his part.
And yet, what Jerry did not know was very much.

He did not know the size of the world.

He did not know that this Meringe Lagoon, backed by high, forested mountains and fronted and sheltered by the off-shore coral islets, was anything else than the entire world.