By the 1970s , however , the grizzly bear 's ( Ursus arctos ) range in and near the park became the first informal minimum boundary of a theoretical Greater Yellowstone Ecosystem that included at least 16,000 square kilometres ( 4,000,000 acres ) .
By the 1970s , the grizzly bear 's ( Ursus arctos ) range in and near the park became the unofficial minimum boundary of a Greater Yellowstone ecosystem .