America’s largest land animal fertilizes—and then mows—its own food. Scientists published a report last week in the Proceedings of the National Academy of Sciences, a science journal. The article says bison spur the growth of the grass they eat. The research could help in the effort to rebuild bison herds in North America.

The bison study took place in Yellowstone National Park. Researchers found that most hoofed mammals must keep migrating to find newer, fresher plant growth. But bison can graze in one area over and over.

Researchers wanted to know why. So they fenced off plots of grass where bison migrate. They compared those no-grazing areas to the grazed ones.

Studies show that the grass where the bison grazed over and over was shorter, denser, and healthier than the other areas.

But there was more to the grass-is-always-greener story.

Remember the lawnmower robot? (See “Robo-Mower Makes Strides.”) God’s giant bison-mowers do even better: Their waste acts as a natural fertilizer. “They drop nutrients back on the landscape, which are then available to plants,” says Yellowstone scientist Chris Geremia.

Keep on munching, bison!

(A herd of bison grazes in the Lamar Valley of Yellowstone National Park. AP Photo/Matthew Brown, File)