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The Cost of the Wild

Restoring an ecosystem to primitive grandeur is no simple matter in a complex world

Pat Shipman

More than Predation

Competition for grass and forage is not the heart of the problem; brucellosis is. Brucellosis is a bacterial disease originally found in cattle that spread long ago to the bison. The disease causes pregnant females to abort their fetuses, expelling fluids and tissues that then infect other animals in the same area. Brucellosis has been eliminated from the domestic cattle population through mandatory annual vaccinations and aggressive slaughter of all animals in an infected herd. About 45 percent of the Yellowstone bison and 5–10 percent of the elk still carry brucellosis. Vaccinating bison only at boundary facilities will probably not reduce the rate of brucellosis infection in the herd long term, but a consistent, park-wide effort would be “controversial, logistically challenging, expensive, and intrusive, with no guarantee of successfully reducing brucellosis prevalence to near zero” according to a 2011 article written by a group of Yellowstone Park rangers in Biological Conservation.

Though all female cattle are vaccinated, the vaccine is not 100 percent effective. If brucellosis is transmitted to their livestock by wildlife, ranchers face the devastating destruction of their entire herd. Further, if only two cases of brucellosis-infected cattle are discovered, the entire state loses its “brucellosis-free” status. Cattle from a state that is not brucellosis-free bring less money, and their transport across state lines is difficult and tightly regulated. The stakes are very high.

Bison straying outside the park are hazed by helicopter and by individuals on horseback or on all-terrain vehicles in an attempt to drive them back into the park. When the grazing is exhausted in the park, some bison refuse to return and face starvation. Those that remain outside the park are rounded up, penned and tested for brucellosis—very stressful events. Animals that test positive are killed. The article by the Yellowstone Park rangers attests: “About 3,100 bison were culled from the [Yellowstone] population during 1985–2000 for attempting to migrate outside the park.”

Culling a once-endangered species that is a vital component of the Yellowstone ecosystem seems wrong. It offends every conservationist’s deepest beliefs. These animals are only reoccupying their former range as circumstances demand (see map). Unfortunately, their presence in cattle-ranching areas and their infection with brucellosis pose a serious economic threat to ranchers.

Some regard the presence of bison as inevitable: “If you don’t want bison on your land, move to Ohio,” one rancher said. Others stress the inherent unfairness of endangering their carefully built herds and lifestyle with a wild animal that is supposed to be kept inside the park. They demand that a management plan be devised for the bison that will protect their herds from the risk of infection.

Bison advocates like the Buffalo Field Campaign demand that the animals be left to roam free and experience the consequences of natural selection. They emphasize that only the Yellowstone herds and those in Wind Cave National Park are free from genes resulting from crossbreeding with cattle—a strategy used by ranchers to make bison more docile.

The Yellowstone Park herds are genetically uncontaminated and have occupied their range since prehistoric times. Whatever knowledge, instincts or abilities have evolved in wild bison to help them survive in a rugged landscape with harsh winters, the Yellowstone herd has them.

Like wolves, bison also pose a danger to humans. Humans can become infected with the brucellosis bacterium, which gives them undulant fever, a very nasty, often incurable, recurrent disease. It is worth stressing that bison are not cute Disney animals; they are 2,000 pounds worth of strength, ferocity and unpredictability. While I was in Yellowstone, a tourist, who foolishly approached a bull bison much closer than park regulations allow, was gored and sent to the hospital. Bison injure more visitors to Yellowstone than bears do.

Wolves and bison are only two of the controversial issues in Yellowstone, our first and perhaps greatest national park. How can we balance the rights of the individual with those of the majority? There is a real price to pay for preserving our wild heritage. We must listen to the opinions of all the stakeholders to negotiate a just and equable solution to these complex problems.


  • Hedrick, P. W. 2009. Conservation genetics and North American Bison (Bison bison). Journal of Heredity 2009:100(4):411–420. doi:10.1093/jhered/esp024
  • White, P. J., Rick L. Wallen, Chris Geremia, John J. Treanor and Douglas W. Blanton. 2011. Management of Yellowstone bison and brucellosis transmission risk: Implications for conservation and restoration. Biological Conservation 144:1322–1334. doi:10.1016/j.biocon.2011.01.003

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