And indeed it’s truly good news. The wolves altered elk behavior and moved them out of fertile valleys and into more sheltered areas, which allowed the willow and aspen trees along the rivers to grow taller. Fewer elk (and more skittish ones among the remaining population) increased the number of berries, which has been good for bears. It has meant more food for rabbits and mice, which has meant more hawks and eagles. More beavers have been able to eat the healthier trees, and their dams provide habitats for many animals. The dams and the trees’ deeper roots have made Yellowstone’s rivers healthier and swifter