I haven't seen the movie, so I had to look up the movie on IMDB.

Buck is the dog in the movie.

This is a tough one.

Terry Notary is also listed in the credits as a Rail Worker according to IMDB. So he is an actor.

This is the thing now, and frankly probably has been ever since they started using actors as references when the character is CGI'd. Are they people "acting" as a reference for a CGI'd character, are they an actor or a Visual Effects crew member?

I suppose you could use other films as a guide where characters are CGI'd, such as Polar Express or King Kong or Avatar.

Or I even suppose that you also could say that these are people similar to puppeteers. Those people never appear on screen either. They represent a character, via a puppet.

Being that Buck is a character in the film, I think that the credit is for a cast member. To me it doesn't matter if it's a puppet or a completely CGI'd generated character. Both "act" as a character seen on screen.

But that's just my opinion and I'm sure others will disagree. But since when, has this community come to an agreement on such things? LOL!!

My feeling is that Andy Serkis is quite frightening.  If he thought we were saying actors who are CGI reference points don't count as actors he would be very angry.  They therefore count as actors.  It's a valid credit.

I'd include him in my own local db. Notary's a legit actor and motion capture performer, but I think this sort of thing is debatable given the rules.

But these people are acting, they are the driving force for the voice and/or character you see on screen. I personally think stunt people you see on screen should get a nod also...but that's just me.