Yellowstone's Bison Still Rule the Road

By 1902, Yellowstone's wild bison were down to about two dozen animals. Poachers had hunted the rest of the herd almost to nothing, and the last holdouts were hiding in a remote corner of the park called Pelican Valley.

The Last Wild Herd Left

Bison once numbered in the tens of millions across North America. By the time the hunting slowed, Yellowstone's Pelican Valley group was one of the only wild herds still standing anywhere in the country.

Congress had passed the Lacey Act in 1894 to punish poachers, but the hunting continued until the U.S. Army, then in charge of protecting the park, stepped up patrols. The wild herd stopped shrinking.

In 1902, the U.S. Army also brought in 21 bison from private ranches in Montana and Texas to rebuild numbers faster, moving them in 1907 to a new outpost called the Buffalo Ranch. Over time those newcomers mixed with the wild survivors and formed the single herd that exists today.

Genetic testing has found Yellowstone's herd carries less trace of cattle DNA than almost any other public bison herd in the country. Older mitochondrial DNA tests found none at all; the most sensitive modern whole-genome tests have found only a trace amount in one animal, far below the levels seen in most other American bison herds.

Nearly 5,300 Bison Today

The National Park Service estimates the park's bison population at close to 5,300 animals before each spring's calving season.

They range across the park's interior, including Hayden and Pelican valleys, moving with the seasons much as the wild herd did before it nearly disappeared.

The Jam Nobody Can Rush

Every summer, tourists driving through Hayden Valley run into the same thing: a line of bison walking straight down the center of the road.

Traffic backs up in both directions, sometimes for a mile, while the herd takes its time crossing or simply ambles down the pavement. The National Park Service calls these "bison jams" and says on its site that they are common enough to plan extra travel time around.

The agency's instructions for drivers are consistent: stay inside the vehicle, keep at least 25 yards away, and never honk the horn or drive toward the animals to move them along.

Why Nobody Argues With Them

Bison look slow, but the National Park Service warns they have injured more visitors than any other animal in Yellowstone, and can run about three times faster than a person.

That combination is why rangers wait the herd out instead of trying to clear the road themselves. The bison that survived a near-extinction by hiding in one valley now set the pace for everyone who visits.