The answer is.
propeller injury
Notice that independently, the prey population goes up, if the predator's population is low. One interpretation is that there are not enough predators to really make a dent in the prey's population. But as the prey's population increases, they become easier targets for the predators since there are so many. As predators feed on prey, the predator's population increases (more food, can sustain a bigger population) and the prey's population decreases. As less and less prey are available to hunt, the predator's population also decreases.
Note that it need not be this cyclical, the trend can go to an equilibrium point where the populations do not fluctuate all that much.
the predator eats the prey limiting them to not overly grow. And the prey do not overly grow limiting the predators population to not overly grow as well. hope that helps
