Pi remarks that this is the very definition of animals, killing without necessity.
On that stormy night, cruising on a ship in the middle of the ocean, Pi lost everything, everything that meant something to him, his family, his protection, the feeling of safety and love. In animals, the urge to kill is separate from the urge to eat. More algae than i could eat? And when I was beyond all hope of saving, he gave me rest.
Pi looks to the meerkats for company while on the island, in place of the humans he longs for.
Many of the things he had to go through made him question God at times and wonder why such a higher power considered so amazing and giving, would allow Pi to go through all this suffering and difficulty.
Eventually the theme of faith leads to the biggest question in the novel after Pi tells two completely different stories of his survival to the Japanese insurance investigators. He believed because he had no other choice. Kumar challenges his Hindu faith in God, this makes Pi realize the positive power of belief and the need to overcome the harshness of the universe.
Without his staunch faith in God, Pi would not have gained the willpower required to prevent him from meeting his demise at sea.