C'mon people. Ambient life? Sure, I want to see a few little animals scurrying around and getting sucked under the wheels of the warthogs, but, a cow? They don't have cows or pigs or anything else on the rings because they would probably over populated the place without predators. So, if there were herbivours and things on halo then there would HAVE to be carnivours there to help balance out the population. I presonally DON'T want to see a cow or pig on the battlefield, maybe a flood infected one back on Earth, thought.