To the OP - animals do have varying amounts of intelligence, but the worth of man is not based on how smart he is (either individually, or as a species) but rather on the fact that he was made in the image of God. The ability to reason as we do could be said to be a consequence of this thing that gives us worth, but it is not what gives us worth itself, and so we should be careful with ideas along the lines of “intelligence gives us worth, these animals appear to have some form of intelligence similar to (if lesser than) what we have, so they must have some amount of/the same/whatever value that we have.” (Which is not to say I think you were saying this, just that many people that bring up animal intelligence start heading in this direction.)
That said, animals are creations of God and deserve respect, and excessive cruelty towards them ought to be avoided. And I would probably agree that the more an action seems to bother an animal, the more justification is required to do it, and so the amount of intelligence displayed by an animal may very well impact how we can treat it. But animals are nevertheless sub-human, and so can be used by humans to meet our needs.
I can’t say whether or not the treatment of animals at seaworld or similar would count as excessive cruelty or not - this would depend on whether or not such really is harmful to the animals (which I suspect is not as clear in one direction or the other as some on both sides would say), and whether or not some good is achieved that justifies it if so (harming animals is not by itself intrinsically evil). But the mere fact that the animals display some amount of intelligence is not enough to make using them for our ends immoral, even if doing so causes them some harm.
I suppose I understand the Greek thought on this [rational soul vs non-rational soul] as you described but you claimed it was catholic teaching and I was looking for a catechism reference or something describing what you spoke of.
Not an explicit endorsement, but a usage of the phrase “rational soul”:
1934 Created in the image of the one God and equally endowed with
rational souls, all men have the same nature and the same origin. Redeemed by the sacrifice of Christ, all are called to participate in the same divine beatitude: all therefore enjoy an equal dignity.
Also, this site has some reference to the same:
ewtn.com/faith/teachings/goda42a.htm (specifically, number 49.)
Many people use the word soul to mean what is meant by “rational soul”, and I suspect that if you make this substitution in the things that you would normally say about souls, you will find no disagreement. (Animals don’t have rational souls, rational souls are immortal, non-rational souls are not immortal (and so animals don’t have immortal souls), etc etc).