And this wouldn't be a huge deal, except the game sort of forces you to play as all of the characters as certain times always call for certain creatures. (darkstation.com)
Certain creatures enable you to grow faster, eventually gaining new body parts, making you a more dangerous predator. (dealspwn.com)
They will have a formation that makes certain creatures harder to hit so you will have to take out the front first and work your way back. (gamefreaks365.com)