An opportunistic predator switches prey, capturing whichever prey species is most abundant. As soon as the prey numbers dwindle and another species becomes more abundant, the predator will consume the more abundant species. In doing so, this predator maintains great biodiversity in the community. This type of predator is called a

The correct answer is keystone predator.

Explanation:

In sustaining the composition of an ecological community, a keystone species plays an essential function. In the absence of keystone species, the ecosystem would fail to exist and would become drastically different. A predator is a classic illustration of a predator, which inhibits a specific herbivorous species from eradicating the dominant species of plants. In the non-existence of predators, the herbivorous prey would increase enormously and would clean the entire essential plant species, and thus, drastically change the significance of the ecosystem.

when it is at an intermediate population density