Which story from Life of Pi do you believe is real: the story with animals or the story with humans?
In my mind, the story that is of course more likely is the story involving the people, the chef becoming the cannibal and in the end Pi deciding that he is going to have to resort to that in order to survive. The fact is that humans will go to incredible lengths, positive and negative, when it comes time to survive, they begin to act far more like animals. So Pi describing them as animals instead of as humans makes a great deal of sense and makes for an amazing story. It is also in some ways easier to believe or accept than the idea of humans eating each other and Pi being in a situation to have to watch his mother being eaten, these things are hard to wrap your brain around.