Really? You cannot fathom an animal population that has exceeded it's ecosystem's capacity and has no predators so needs to be culled?
Doesn't happen.
That situation always auto-corrects as resource availability shifts.
What does happen is humans find things like mice / locust / kangaroo plagues inconvenient, so we decide to intervene.
It's not like lions get tired of all those pesky gazelle getting up in their grillz and find the need to get about in helicopters thinning the herd.