Yeah. I noticed that, too. Kind of like the third wolf wasn't as high-ranking as Hutch and Cando, so he or she (hard to tell if it's supposed to be a boy or a girl) would just go along with whatever Kate, Hutch and Cando did.
I think that he was just there for backup probably, its not exactly easy for a wolf to take down a 600lb caribou, I've watched them take down elk before on video and sometimes it takes 6 or more of them to do it.