" Modern, well-documented research demonstrates that apex predators such as wolves play keystone roles in keeping prey populations healthy by culling the weak and infirm. They also keep ungulate numbers in balance with habitat; wolf reintroduction into Yellowstone resulted in a stunning transformation of overbrowsed, depleted river and stream corridors, to the benefit of many species, from aspens and cottonwoods to beaver to songbirds to cutthroat trout. An "

― Nick Jans , A Wolf Called Romeo