Replaces Fat tissue.Okay digestion is a wall of text but it adds nice points with a card.It adds a carnivore approach to it and it enables the carnivore to eat chewy tasty poisonous frogs without any side effect.Carnivore side also allows you to eat above your population if you want to and helps you to attack maybe a second or third time.However since it's a trait afterall your carnivore will be left with ony one slot for an aggressive trait.Concerning avian carnivores(guess those are vultures :)) you don't have to pay the extra bodysize upkeep.