The circle of life is a philosophy that represents the infinite nature of energy, meaning if something dies it gives new life to another. Of course, this is merely a cover for the Lions true purpose of preserving their livestock. It's one thing to sing along to this tune when you are a carnivore at the top of the food chain. But when your a herbivore struggling to survive and provide for your litter, spending your days looking for food while running from predators who want to eat you alive, this is total BS.
These poor creatures are expected to go along with this hierarchy, worshipping the Lions of the pride lands as leaders, only to be hunted down and suffer a slow horrific death with chewing and go "oh well circle of life lol". The animals of the pride lands decide that they don't much care to be treated this way any longer. They rebel against their masters, slaughtering all the Lions and any other carnivores in the area, ushering in a new age. They are now able to live in peace and harmony, no longer having to look over their shoulders.
However, there is a problem. Many herbivores reproduce quickly and in large liters. With an absence of predators, there is a real danger of certain species exploding in numbers, leading to overgrazing, deforestation, and other problems.
What natural mechanism does an environment need in order to prevent this from happening?