Populations of typical prey animals, such as deer, might exceed the carrying capacity of an ecosystem if top predators, such as mountain lions, are removed.
Without the mountain lions, increased numbers of deer may reduce the food supply available to other herbivores, such as field mice and crickets. As a result, populations of deer, mice, and crickets might decline, causing a population decrease in species that feed on these organisms as well.
This example implies that properly functioning predator/prey relationships