He has been living with one in a lifeboat for some time. He hasn't been around humans since his parents died. So his mind went into survival mode. And sometimes survival mode means animal-like behavior. “I will further confess that, driven by the extreme of my need and the madness to which he pushed me, I ate a little of his flesh. I mean little pieces, little strips that I wanted for the gaff hook that, when dried in the sun, looked like regular animal flesh. They entered my mouth almost unnoticed. You must understand, my suffering was incessant and he was already dead” (Chapter 91). He just ate the French Chief with Richard Parker. Sure, he was dead, but that all the more proves that Pi had adopted animalistic behavior to survive. Pi wouldn't have done this alone. In fact, the French chef would not have died if Richard Parker had not been there. Pi wouldn't have gotten this far without him. He would have died in the middle of the ocean if Richard Parker hadn't been there to mentally force Pi to fight for