The relationship between an ecosystem's predators and its prey is also self-regulating.
If there are many prey in an ecosystem, there is a lot of food available for predators and they will be able to have more young, so in a short time the number of predators will increase.
The high number of predators will need many prey to feed, so the number of prey will decrease, leaving less food available to predators. As a consequence, some will die, have fewer young, and the number of predators will decrease. Then, as the predators will hunt less prey, the number of these will increase, returning to the starting point, keeping the balance between the two populations stable.
Simulator: Predator-prey model.
Simulator: Rabbits and wolves (rabbits and wolves).