The return of wolves benefits the grizzly bears because______.

(3 - 1)Scientists say the return of wolves to Yellowstone National Park in the American state of Wyoming has boosted the diet of a rival predator, the grizzly bear.
    Wolves returned to Yellowstone nearly 20 years ago, put back into the wild to prey on the growing elk population. Elk were overgrazing the grassland, causing damage to the precious ecosystem. Now scientists say the wolves have had benefits for another predator, the grizzly bear.(3 - 2)Trees and shrubs are springing back up, bearing nutritious berries, a valuable food source for the grizzly bear. Wild fruits are a key part of the bear’s diet as it gains weight before hibernating.