"That’s right, it turns out that all animals can speak; they just choose not to do so. If they do, it’s a violation of an oath they took."

This is a principle I have adopted in my own fiction. The "choice" to speak is made based on whether they can trust picked humans with that knowledge. And the "oath" has much to do with Adam's fall ("In Adam's fall, we sinned, all...").

I also have been a follower of the Garfield camp for a long time, but this particular publication (to say nothing of the film) escaped my knowledge until now. If anything, that movie would likely have been much better than the atrocious Garfield films that have since been produced...