question: How did wolves in Yellowstone help beavers eat well ?
answer: wolves often kept animals from grazing in riparian areas , which protected beavers from having their food sources encroached upon
turker_answer: Wolves in Yellowstone helped beavers eat well because they often kept animals from grazing in riparian areas , which protected beavers from having their food sources encroached upon .
rule-based: Wolves in Yellowstone helped beavers eat well by wolves often kept animals from grazing in riparian areas , which protected beavers from having their food sources encroached upon .