A symbol of the wild west, the American bison is the heaviest land mammal in North America. Also called the American buffalo, the bison has a large head with relatively small, curving horns. It has a shaggy coat of brown hair on its shoulders and legs, while its body has shorter, finer hair. Bison are 5 to 6½ feet long and weigh 900 to 2,200 pounds. Males are larger than females on average.

Historically, bison numbered an estimated 20 million to 30 million. Today, approximately 250,000 remain in the United States. Of those, only 16,000 roam in the wild. Yellowstone National Park has the only population of free-roaming bison.

Bison typically live between 12 to 15 years and inhabit the Great Plains, prairies and forests. Bison eat grasses and sedges, moving continuously as they eat so that they rarely overgraze an area.

Bison live in herds of 20 to 50 animals. The females, or cows, lead family groups. Bulls (males) remain either solitary or in small groups for most of the year. Bison travel as a group and roam great distances in the wild. They can reach speeds of up to 30 mph.

Females produce one calf after a gestation period of nine and a half months. Calves are born in late April to mid-May. The cow protects the young. The offspring may remain with the mother for as long as three years after birth.


Shooting bison for their hides was a favorite frontier sport in the 19th century. Hunters practically eliminated the bison by 1890. In 1893, the first efforts were made to protect the animals. Today, the bison of Yellowstone National Park face the threat of slaughter when they exit the park and enter the state of Montana.

Along with the bald eagle, the bison perhaps best symbolizes the spirit of American wilderness. While many people are aware that both animals teetered on the brink of extinction in the past due to human encroachment, few realize that wild bison continue to be the victims of a calculated, annual slaughter in the Greater Yellowstone Area.

During the mid to late 1800s, government agents orchestrated one of the most aggressive and wanton animal massacres in history, killing bison indiscriminately in an attempt to subjugate Native Americans. With the addition of market hunters and settlers killing bison for profit and for fun, America's wild bison herds were reduced from an estimated 60 million to perhaps as few as 100. With the establishment of Yellowstone National Park in 1872 and the National Park Service in 1916, the 25 bison remaining in the Park finally were afforded some protection. Initially, management policies allowed for the active manipulation of populations by culling what was perceived as "surplus" animals. But eventually, the management strategy evolved to an approach which permitted natural regulation to occur, for the most part letting nature take its course rather than relying on human intervention.

This was good news for the bison, but sadly their fortune was short lived. Since the mid 1980s, more than 3,000 bison have been massacred under the supervision of government officials bowing to the pressures of the livestock industry and its cohorts. The livestock industry and federal and state livestock agencies contend that bison can transmit the Brucella abortus bacteria to cattle under natural conditions. In reality, there has never been a documented case of this occurring. Despite this fact, they continue to wage a war against Yellowstone bison.

In 1917, officials discovered that some Yellowstone bison were infected with Brucella abortus, the bacteria which causes the disease brucellosis in domestic cattle. In cattle, the disease produces spontaneous abortions, but bison do not appear to be similarly affected. In fact, over the past 80 years in the entire Greater Yellowstone Area, there have been only four documented bison abortions, which may or may not have been caused by the bacteria.

Over the past decade, bison have been emigrating from the Park over its northern and western boundaries into the state of Montana during winter months. Because of several mild winters, and the National Park Service's continued grooming of snowmobile trails which makes it easier for bison to exit the Park, more and more bison have been stepping hoof over Park boundaries.

The U.S. Forest Service issues grazing permits on lands adjoining Yellowstone National Park, generally for the months of June through October. Cattle grazing is even allowed in Grand Teton National Park. The interests of wildlife, and not cattle, should take precedence on public lands. The grazing allotments should be either closed or modified to minimize any contact between bison and cattle. Also, mandatory vaccination of domestic calves against brucellosis within the counties surrounding the Park could further reduce the risk, if any risk exits at all, of infection. Currently, vaccinations are not mandatory in Montana or Wyoming.

In addition to bison, elk can also be infected with the bacteria and can carry the disease. With more than 90,000 elk in the Greater Yellowstone Area, the likelihood of eliminating the bacteria using available technologies is virtually nonexistent. Moreover, if all infected bison were destroyed, exposure to elk would result in reinfection in the remainder.

This is particularly a problem in Wyoming where over 23,000 elk congregate on artificial feedgrounds, creating prime conditions for bacteria transmission. In fact, bison from Grand Teton National Park, just south of Yellowstone, have discovered the "free meals" being provided on the National Elk Refuge each winter in the Jackson Hole area. It is speculated that this herd of bison contracted the bacteria from elk on the feedground.

State officials rarely admit that elk may also carry the disease. Elk, of course, are a prime money maker for Montana and Wyoming state officials, who encourage propagation of elk herds so they can profit from the sale of sport hunting licenses.

Ironically, bison are being targeted allegedly to protect the livestock industry, but the general consensus among scientists is that cattle probably introduced the bacteria into the Yellowstone bison herd shortly before 1917.