How do populations of predators and prey vary in predatism?

Whenever a predator population enhances at the first moment the prey population tends to decrease. At a second moment the decrease of the prey population and the bigger population density of predators cause the predator population to reduce. The prey population then reverts the tendency to reduce and starts to grow.

If variations in the size of populations occur in an unexpected intensity (dissimilar from the usual intensity of the ecological interaction) for example, due to ecological accidents killing much prey, the prey-predator equilibrium is disturbed and both species can be harmed. The existence of the predator sometimes is fundamental for the survival of the prey population, as the absence of predatism favors the proliferation of the prey and, in some cases, when the excessive proliferation creates a population size over the sustenance capacity of the ecosystem, environmental degradation happens and the whole prey population is destroyed.