Bison on the Firing Line

Around Yellowstone, rancher concerns about cattle disease are colliding with wildlife protection on public lands.

• Roger Di Silvestro
• Dec 01, 1996

The wholesale slaughter of America's bison stopped near the end of the 1800s, but federal and state livestock agencies are trying to revive the practice for Yellowstone National Park bison, which the officials see as a threat to domestic livestock. As a result, at least one state livestock agency is beginning to set wildlife-management policy on federal lands in the Yellowstone area, a move that some experts call a dangerous precedent. State officials counter that they have been forced into the role by intransigence on the part of the National Park Service (NPS).

The livestock agencies' concern centers on a cattle disease that bison may carry--brucellosis. The illness, which probably came into North America with domestic animals from Europe, can cause abortions in livestock, yielding severe economic impacts. Infection occurs when cattle come in contact with the aborted fetuses. The disease also can be passed to calves in milk.

About 60 years ago, when brucellosis seemed a burgeoning threat to American livestock, the U.S. Department of Agriculture launched a program to test cattle for the disease, kill animals that tested positive and vaccinate negative animals. This approach, conducted by the Animal-Plant Health Inspection Service (APHIS), has nearly wiped out brucellosis in U.S. cattle.

An estimated 50 percent of Yellowstone's 3,500 to 4,000 bison probably would test positive for the disease. However, testing positive and carrying the disease are two different things, says Mary Meagher, a mammalogist who has studied park bison for more than 30 years as a member of the park staff and as a scientist with the National Biological Service. A positive test can indicate that a bison is carrying the disease, she says, but it also can mean that the animal once came into contact with brucellosis bacteria but no longer harbors the organisms or that the animal carries the bacteria but is not infectious.

Clarence Siroky, Montana state veterinarian, nevertheless perceives park bison as a threat to area cattle, arguing that infected bison abort calves. Meagher demurs. "The whole brucellosis fear is founded on extrapolation from how the disease effects cattle," she contends. But what happens in cattle does not necessarily apply to bison, she says. "Evidence to date suggests that bison rarely abort," she says, "even when they have brucellosis, making the risk of transmission from bison to cattle very small."

Not a single documented case of brucellosis transmission from bison to cattle has ever occurred in the wild," says Rich Day, director of the National Wildlife Federation's (NWF) Northern Rockies Natural Resource Center in Missoula, Montana. Nevertheless, the brucellosis question has created a tug of war over wildlife managment in the Yellowstone area. APHIS, the Montana Livestock Department and other livestock interests want the NPS to inspect the bison herd, kill animals that test positive and put ear tags on those that test negative. Subsequently, almost any bison that leave the park could be shot.

This policy, says Paul Nicoletti, a veterinarian and bison expert at the University of Florida, "would result in the near decimation of the bison herd." And inevitably the plan would fail, says Meagher, because the disease occurs widely in elk. "I see no way brucellosis can be eradicated without eradicating wildlife," she says.

Bison that leave the park, primarily to escape severe winters, already are being shot by agents from the Montana Department of Livestock, who killed 455 of the animals during the first half of 1996. Ironically, itinerant bison wander largely into national forests. "So essentially the state is taking over wildlife management on national public lands," Day says.

Siroky maintains that the state has had to step into the breach because NPS does not control the animals. "It's not that we like to do it," he says. He alleges that park officials refuse to test and cull the herd because of an NPS policy to maintain the bison without human interference.

Nonsense," says Steve Torbit, staff scientist with NWF's Rocky Mountain Natural Resource Center in Boulder, Colorado. "So far, of various state and federal agencies that have formed a committee to resolve the brucellosis problem, only the park service is willing to commit its share of promised funding." APHIS, he says, is simply trying to expand its authority by transferring management of wildlife on public lands to the agriculture community.

What we need is a common sense solution," says Day. "Measures such as moving cattle away from public lands when bison arrive and vaccination of cattle will solve the problem without killing off a wildlife population. The bison is a wild animal, and on public land it should be managed like a wildlife species."

Roger is a senior editor of this magazine

Safeguarding The Bison

In early 1996, the National Wildlife Federation adopted a resolution supporting free-ranging bison on public lands in the Yellowstone ecosystem. If you would like to be kept informed on this and other issues concerning wildlife management in the northern Rockies, please write: NWF, Rocky Mountain Natural Resource Center, 2260 Baseline Road, #100, Boulder, CO 80302.