In the western U. S., ranchers aggressively killed wolves because they posed a threat to their cattle. As the wolf population declined, the deer population began increasing. As a result, the surrounding forest ecosystems experienced increasing damage. The large number of deer ravaged vegetation and destroyed young trees. The entire ecosystem became degraded until wolves became protected when they were determined to be an endangered species. Based on this information, what can you infer about the role of the wolves in this ecosystem? A.
They are a pioneer species.

B.
They are a keystone species.

C.
They are a prey species.

D. They are a competitive species.