MOIESE (AP) -- In his best-selling history, ''Undaunted Courage,'' Stephen Ambrose describes the buffalo as ''the quintessential animal of the North American continent'' and the ''magnet that drew men to the West.''
The bison ran free a century and a half ago. To some degree, they still run free on the 18,500 acres of the National Bison Range in Moiese, north of Missoula.
But for two days every October, during the annual bison roundup, the 500 bison on this refuge are rousted from their natural lifestyle and subjected to many of the same treatments performed on their domesticated bovine counterparts.
''This is not a happy day for bison,'' says Pat Jamieson, outdoor recreation manager for the range. ''They don't like what's going on, and they don't like people.''
Jamieson, a 10-year veteran employee of the Moiese preserve, helps coordinate the event, along with about 30 other helpers.
They weigh, brand and draw blood from the animals and spearhead educational efforts for the 3,000 onlookers and more than 1,000 teachers and students.
''I always say, 'I'll go deal with 500 bison if you want to come over here and deal with 1,100 students and kids,''' Jamieson jokes.
She says her colleagues never take her up on it.
In the days before the event, range employees round up the herd into one large fenced field.
It's on a hillside overlooking the corral system.
On roundup day, four or five skilled riders ''cut'' 20 to 30 bison at a time from the herd and run them down the hill behind a thundering cloud of hooves and dust into the chutes.
Cutting is the most dangerous part of the roundup.
Horses have been gored, butted and bruised, arms have been broken and backs injured. At least one buffalo has been killed.
However, none of the workers has been seriously injured since it all began in 1923.
''We've had a couple times when we've had people get thrown and that always worries me,'' said range employee Bill West.
When the riders bolt in with a cut, a spectator might see and feel the same power and magnificence the bison must have displayed two centuries ago when making their rumbling, headlong flights by the thousand across the prairie.
To emphasize the danger and power of a herd of bison on the run, West told the story of when he watched a buffalo calf die instantly from a blow in the chutes.
''They were going full blast and then (the calf) got pushed over at the last second and hit the chute so hard it broke its neck.''
This year's event saw no such accidents, but one belligerent bull butted the headlight out of a truck trying to round the animal into the holding pens.
Another bull in the chutes broke a cable on the weighing scale.
Such outbursts give spectators a new profound respect for these immense animals that seem so docile in their native habitat.
Originally, the corral system at the bison range was built of wood, but constant repairs led to the decision to upgrade to a ''bisonproof'' metal system, constructed from guard rails and I-beams.
It was installed in 1993 for $200,000.
Now, the gates are deafening, as the bang of the bison's throes reverberates like thunder over the screams of the school-age onlookers.
''(The bison) can't beat them up, so they'll last,'' said West. ''They're good, they're just loud. When you're down in that hole it's hard to talk to each other.''
Once weighed, the bison are separated by the specific work to be done.
Usually, it's based on age and sex.
The year's calves are branded with an age-sex mark and tagged with a computer tracking device.
Blood and hair samples are taken for vaccine research and to track the herd's genetics.
The herd's maximum is 500 head, with 370 to 390 animals comprising the ''base herd.''
Management has determined over the years that those numbers are ideal for the range's 18,566-acre prairie ecosystem.
Of the base herd number, 110 to 120 are breeding-age females.
An average of 80 percent successfully bear calves in April and May.
The refuge also strives for a specific age-sex ratio to maintain the herd's social and genetic purity.
This means that certain ages and sexes of bison need to be removed each year.
About 25 percent are removed from the range. Some go to research facilities, others are donated to the Inter Tribal Bison Cooperative, and the rest are auctioned by sealed bid.
''We try to emulate this population as if it were in the wild,'' said Dave Wiseman, range director.
The largest bull at the 2001 roundup tipped the scales at more than a ton -- 2,145 pounds.
The tracking program started three years ago. If a specific animal's blood work exhibits disease or the bison shows signs of sickness, the staff can quickly locate that animal or its blood data.
The bison range has been brucellosis-free for 30 years; therefore, the bison are not vaccinated for that disease.
However, blood and hair samples are taken and archived so any disease outbreak may be tracked to a specific animal or year.
''It's all part of our disease-management program,'' said range wildlife biologist Lindy Garner. ''Bison are susceptible to any of the bovine diseases, so (a case of disease) is probably going to come down sooner or later.''
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