Page "Herbivore" Paragraph 14

According to the theory of predator-prey interactions, the relationship between herbivores and plants is cyclic.

When prey ( plants ) are numerous their predators ( herbivores ) increase in numbers, reducing the prey population, which in turn causes predator number to decline.

The prey population eventually recovers, starting a new cycle.

This suggests that the population of the herbivore fluctuates around the carrying capacity of the food source, in this case the plant.