https://apnews.com/65b82c8046db4ff48970865d8645c82a

MISSOULA, Mont. (AP) — A study of grazing in Yellowstone National Park found that bison essentially mow and fertilize their own food, allowing them to graze in one area for two to three months during the spring and summer while other ungulates have to keep migrating to higher elevations to follow new plant growth.

Hundreds of bison grazing in an area stimulates the growth of nutritious grasses, in part because their waste acts as a fertilizer, according to research published this week in the Proceedings of the National Academy of Sciences.