According to the original creators (https://en.wikipedia.org/wiki/Minsc), Boo is just an ordinary hamster. In fact, I wonder if this is one of those "Lassie" situations where several different animals have played the same part? Perhaps I shall wander in the Mists of the Unknowing to ponder this some more ... or perhaps not.

What I find much more interesting is that Minsc has a younger sister! Now that is something a writer could work with, eh?