Hyena - the cook from the ship, kills both the "zebra" and the "orangutan", represents the ruthless evil in the world
Zebra - a young Chinese sailor whose leg is broken, represents the vulnerable things in life and how they are attacked (like by the "hyena" who eats the zebra )
Orangutan - Pi's mother, represents safety and protection
Tiger AKA Richard Parker - Pi himself, represents Pi's inner strength (when Richard Parker disappears once Pi is on land again, it shows he was never real, only what Pi needed for strength), kills the "hyena"
Also, this semester we are going to read Animal Farm by George Orwell, which also includes symbolism between animals and humans.