What America Lost When It Lost the Bison

[Elderberry]

The Atlantic by Ed Yong November 18, 2019

By migrating in huge herds, bison behave like a force of nature, engineering and intensifying waves of spring greenery that other grazers rely on.

Chris Geremia was surprised. After considerable effort, and substantial risk to life and limb, he and his colleagues finally had the results from their decade-long experiment, and those results were both clear and unexpected: Bison do not surf.

Specifically, bison (or buffalo) don’t follow the waves of new shoots that burst from the ground every spring. This phenomenon, known as surfing the green wave, allows animals to eat plants at their most nutritious, when they’re full of nitrogen and proteins and low in indigestible matter. Such freshness is fleeting, and so grazers undertake large migrations to track the new greenery as it crests across the landscape. Over the past decade, scientists have shown that mule deer, barnacle geese, elk, elephants, Mongolian gazelles, and a dozen other species all do this. Geremia wanted to see whether bison, which once formed the largest grazing herds in North America, follow the same pattern.

Beginning in 2005, he and his colleagues started putting GPS collars on bison in Yellowstone National Park, home to the largest remaining herd in North America, and the only one that truly migrates. Their sociable nature makes for an impressive spectacle, but also creates a problem: When you tranquilize one of them, the others tend to surround their fallen herd-mate. “It took a few years to learn the confidence to walk into this group of a hundred animals, each weighing between 1,000 and 2,000 pounds, and put a collar on the one that’s sleeping,” says Geremia, who works at the National Park Service. “Most of the time, the others just move away.”

Once it had collared enough bison, the team used satellite images to see whether the animals’ movements matched the appearance of new greenery. “They really didn’t,” Geremia says. “They start to surf, but then they stop,” allowing several weeks’ worth of fresh vegetation to pass them by.

More: https://www.theatlantic.com/science/archive/2019/11/how-bison-create-spring/602176/