YELLOWSTONE NATIONAL PARK, Wyo. - It's just after lunchtime, but it's already been a long day. Blood samples were taken earlier from several dozen restless bison herded into a capture pen on the north end of the park. Now, the samples have been tested and it's time to find out who stays, who dies and who gets a shot of vaccine. Rick Wallen, a Yellowstone wildlife biologist, emerged from a trailer with a clipboard and climbed onto the grated walkways overlooking the holding pens and chutes. As two bison moved into the chute below, a crew member called out the four-digit number on the sticker affixed to the bison's hides. Wallen checked his clipboard and found both tested positive for exposure to brucellosis. "Ship," he said. The news was relayed by hand signals - an unmistakable thumbs down - and the bison were herded toward a pen where they would be sent to slaughter the next morning. Next up was a yearling bison skittering wide-eyed through the chute. "Keep," Wallen announced after checking his notes. The bison, soon clamped into a narrow passageway, was the first that day to get a syringe full of RB51, a vaccine designed to protect animals from brucellosis. Throughout the afternoon, bison were sorted, some were vaccinated and about half that tested negative were slated for slaughter. At times the capture facility, where several of the animals had red gouges from tussles with their pen-mates, seemed more like a domestic cattle operation than a place for Yellowstone's iconic wild bison. The Stephens Creek bison pen, tucked behind a locked gate and down a gravel road, has been a busy place the last two months. So far this year, 464 of Yellowstone's estimated 4,200 bison have been captured. Of those, 264 have been taken to slaughter and 198 are being held until food conditions improve in Yellowstone. The activity - hazing and capturing bison that might leave Yellowstone - is nothing new. What's new is a push to vaccinate some of the bison that are captured. State and federal officials believe that the vaccinations can reduce the risk of transmitting brucellosis from the park's bison to cattle outside the boundaries. Yellowstone officials this year began giving shots to bison calves and yearlings that had already tested negative for exposure to brucellosis. About 111 have received the vaccine so far. The vaccination program is expected to continue next year on the north end of the park. Also, Montana Department of Livestock officials are preparing to conduct a study about whether a similar program should be started for bison that leave Yellowstone's western boundary. The effectiveness of the vaccination on bison, though, is unclear. In one controlled test, RB51 was able to help 60 percent of vaccinated calves fend off brucella bacteria. Elsewhere, though, the success rate isn't as good. "So far there is no consensus on efficacy. Some indications of protection have been found in some studies; others have failed to find any protection," said a 2002 paper on RB51 bison vaccine written by two scientists from the U.S. Geological Survey and the U.S. Department of Agriculture. Yellowstone officials in the mid-1960s tried a version of the capture, test, slaughter and/or vaccinate program but soon scrapped it. "These efforts were reviewed by park management and determined to be ineffective and 'never-ending,' " according to background information in the current Interagency Bison Management Plan. Wallen said RB51 is a better option than a predecessor, known as Strain 19, but uncertainties about RB51 remain. Park officials put ear tags on the vaccinated bison this year and will test their exposure to brucellosis if the bison are captured again. That's the best plan so far, Wallen said, but technological advances could improve the program. "There are a lot of different things happening in the world of vaccines, some very promising studies using DNA," Wallen said. The Department of Livestock also wants to study how a vaccination program might work on the west side of Yellowstone, where bison often wander out during the winter. "The goal is to increase overall herd immunity and try to prevent infection within the herd," said Karen Cooper, a Department of Livestock spokeswoman, adding that the state and federal plan is aimed at protecting cattle from brucellosis while maintaining a wild bison herd. But Ted Fellman with the Buffalo Field Campaign, a group fighting against the bison hazing and capturing program, said the vaccination program is a short-sighted way to deal with a "problem that doesn't exist." "By vaccinating them and holding them in captivity and ear-tagging them - it's turning the wildlife of Yellowstone into livestock," Fellman said. "It's appalling that the Park Service would treat them that way."
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It probably was cattle that first spread brucellosis to Yellowstone's
bison.
Cows came to the park with people who lived and worked at
Yellowstone. At Buffalo Ranch in the Lamar Valley, bison probably
came in contact with infectious aborted material left behind by
cattle, according to Mary Meagher, a former Park Service scientist
who researched the origins of the disease in Yellowstone.
Brucellosis was first diagnosed in the Yellowstone bison in 1917.
"It pretty well comes back to the Buffalo Ranch," said Meagher, who
retired in 1997.
Over the years, the bison population fluctuated but concerns over
brucellosis remained. Nearby ranchers were especially worried that
the contagious disease, which can cause abortions and other problems,
would infect cattle herds outside Yellowstone.
In Montana, livestock officials remain concerned that the bison could
cause the loss of the state's brucellosis-free status, which would
mean increased measures and costs for shipping cattle across state
lines.
A plan approved in 2000 by Montana and federal agencies, including
the Park Service, allows bison that leave the park - or, on the north
end, appear to be headed for the border - to be hazed, captured,
tested and sometimes sent to slaughter.
Last year, 231 were killed after being captured on Yellowstone's
northern end. More than 1,000 were sent to slaughter in the winter of
1996-97.
Earlier this winter, park officials estimated there were a record
4,200 bison in Yellowstone. But in mid-February, the fluffy snow on
the park's northern range became packed and hard. That makes it more
difficult for bison to get to the food below, so they migrate north
in search of lower elevations and more to eat.
Over the course of several weeks, hundreds of bison were taken to the
Stephens Creek facility. About half tested negative for exposure to
brucellosis and will be held in a pasture until later this spring.
While much of the focus is on the bison captured on the northern end,
Wallen said it's easy to forget about the other thousands of bison in
Yellowstone's interior.
"Even though we handled some 460 animals, there are still over 3,500
that we haven't touched on the landscape. That's twice what was there
20 years ago," Wallen said.
Eventually, the vaccination program could lead to a more hands-off
approach to bison - or at least an expansion of their range, Wallen
said.
"We're trying to develop a program so that the (Montana) state
veterinarian has a greater confidence that there'll be no exposure
risk to livestock he's charged to protect," Wallen said.
For now, though, the vaccinated animals aren't given a free pass to
wander outside Yellowstone and the prospect of claiming that there's
no risk of bison transmitting the disease to cattle is slim.
"It's not zero right now," Wallen said. "It may never be zero."
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By the numbers:
The winter of 2003-04 has been a busy one for crews trying to keep
bison from leaving the northern end of Yellowstone National Park. A
look at the numbers so far this year:
464 captured at the Stephens Creek pen and pasture
264 sent to slaughter
198 being held for release later this spring
1 bison died in captivity
1 bull bison shot
111 or 113 calves and yearlings vaccinated
4,200 estimated in Yellowstone at the beginning of the winter

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