Dru Dixon, who filmed the shooting for bison advocacy group Buffalo Field Campaign, said it took "half an hour to 45 minutes" and four additional bullets for the bull to die.

A group of four other bulls surrounded the carcass, Dixon said. The hunter threw rocks at the live animals, striking them in the head and flanks before they moved off.

The hunt will allow up to 50 of the Plains bison, often called buffalo in North America, to be killed in the three-month season that opens Nov. 15. A lottery for 24 permits drew nearly 6,200 applicants, including an unsuccessful Montana Gov. Brian Schweitzer.

Sixteen additional permits were reserved for native American tribal members, and 10 went to hunters who had drawn permits for a previous hunt that was cancelled.

Hunters typically eat any bison they kill and sometimes mount the head and horns.

During the 1980s, Montana's bison hunts featured state game officials phoning hunters whenever bison strayed out of the sanctuary of Yellowstone National Park. Wardens led hunters directly to grazing buffalo, prompting one animal rights advocate to liken the hunts to shooting parked cars.

Facing nationally televised protests and tourist boycotts, the Montana legislature banned bison hunting in 1991.

This year's hunt was designed to quell past criticisms. It takes place across a 450,000-acre (182,000-ha) area. Regulations forbid game officials from helping, and hunters are all required to attend classes on the rules of the hunt.

At the turn of the 20th century, only 23 bison survived in Yellowstone National Park. The herd now numbers around 4,900.

For opening day, Montana's Department of Fish, Wildlife & Parks beefed up law enforcement presence in case tempers flared between hunters and protesters. "We had some concerns that bison hunters might be harassed and we're here in case anything like that happens," said Pat Flowers, a regional supervisor.

Few hunters took the field, however. "I think many of our hunters considered whether they wanted to be involved in an opening day circus, and apparently many chose not to be," she said.