ANTELOPE ISLAND, Utah - "How do you move a 2,000-pound bison?" a rider on a horse next to me asked. The punch line? "You don't."

Buffalo don't herd easily. If pushed too hard, they lower their heads and charge at anyone dumb enough to get in the way.

But that is exactly what we were trying to do - about 150 riders - as we trotted across a flat field on Antelope Island in Utah's Great Salt Lake. Ahead of us, a herd of about 250 bison - a woolly, snorting blanket of black shoulders and rising dust - shuffled toward the corrals on the north end of the island. To move the animals, riders whooped like warriors. One rider snapped a bullwhip.

In the commotion, at least eight riders were thrown to the ground, and one suffered a broken wrist.

Still, that's the kind of excitement that draws riders to the annual Bison Roundup on Antelope Island, one of the country's few buffalo roundups that allow untrained volunteers to herd these surly, one-ton creatures.

At other roundups - the most famous takes place every September at Custer State Park in South Dakota - visitors stand behind fences as professional cowboys do the hard work. But on Antelope Island each fall, any adult with a horse and the $25 admission fee can help herd bison into corrals for checkups and inoculations. (To ensure that the population does not exceed the island's food supply, some are sold at auction.)

As a kid, I fell in love with the movie Bless the Beasts and the Children, about a group of misfit boys who sneak away from summer camp to save a herd of buffalo from certain death. Since then, I've been mesmerized by the sight of brawny bison rumbling across open fields - a timeless image, like thunderclouds forming, or whales breaching the surface of the sea.

I thought I was alone in my buffalo fascination until I arrived on this 28,000-acre island in mid-October and watched a stream of pickup trucks, horse trailers, and RVs roll onto a grass field. Some of these fellow bison fanatics traveled as far as 600 miles to spend three days enduring freezing temperatures, choking dust clouds, and sore keisters to marvel at this iconic symbol of the American West.

Even Buffalo Bill Cody had a soft spot for these beasts.

Cody, an Army scout and Pony Express rider, killed thousands of bison to provide meat for workers on America's expanding railroads in the mid-1800s. Millions of buffalo roamed the Plains from Mexico to Canada - so many that when herds crossed railroad tracks, trains were delayed for up to half a day.

"The moving multitude . . . darkened the whole plains," wrote Meriwether Lewis, who along with William Clark encountered a herd at South Dakota's White River in 1806.

The railroad companies responded by allowing passengers to shoot the buffalo from the rail cars. In a few short decades, American Indians, hunters such as Cody, and others slaughtered so many buffalo that the herds dwindled to 800 animals. Shamed at the widespread massacre, Cody later joined efforts to preserve the animal he became famous for hunting.

Eventually, preservation efforts rescued the bison from the brink of extinction. Today, about 500,000 bison roam public and private lands; the biggest herd, about 4,000, grazes in Yellowstone National Park. (The terms bison and buffalo are used interchangeably, although bison is the generic name. Biologists note that the American bison is only distantly related to the water buffalo and African buffalo.)

The night before the roundup, I shivered in a tiny tent on a lumpy grass field near Fielding Garr Ranch, the horse-rental concession on the south end of the island.

Before I arrived, state park officials told me that most bison wranglers camp on the island during the three-day event. Clearly, I didn't understand their definition of camping.

As I pitched my tent, I watched a caravan of expensive RVs, campers, and trailers roll onto the island to form a makeshift village. That night, I listened to the rumble of gas generators and neighing horses.

The roundup began early the next morning with a mandatory briefing. An assistant park ranger warned us that bison are not as docile as their bovine cousins. When buffalo get angry, they lift their tails straight up and charge. Among the island's bison, the ranger told us, are several lone bulls - mean, stubborn beasts that won't associate with the herd. Those rebels that aren't corralled on the first two days will be herded later by helicopter.