"Uh. He tries to assert his dominance, not prove his superiority. I imagine if I showed another animal performing tricks he wouldn't want to prove he can do them too- just show off until they admit defeat and treat him as their master."

Rex is absolutely wrong about this. His hesitance to let Indrik interact with others has kept him from discovering that Indrik is smarter and more importantly more prideful than he seems- in fact, part of the reason he acts so stupidly is because he hasn't had much to learn. Though...

"I don't think it could work with cats, especially. They don't like me."

Cats hate him, in fact.