There isn't a verb in the sentence for "I have". I think that would be something like, "tha cluasan mòra agam" (I possess big ears) or "tha cluasan mòra orm" (I have big ears on me).
But both of those are a guess based on other comments Joanne has made (there was a thread about grey hair where a physical characteristic was orm instead of agam) and "cluasan" being feminine (so mòra instead of mòr, based on a Gaelic study book from almost 125 years ago...).
For sure, though, it's because of "mo" and no "I have" verb.
I'm starting to feel like our study times tend to very closely align!! =)