A state with infected cattle or bison may also be subject to restrictions imposed by other states. In the early 1960s, however, elk kills initiated by park officials to reduce the size of a herd that was considered too large, led to a public outcry, studies, and U. S. Senate hearings on Yellowstone’s wildlife management policy. According to park staff, although little information was available on how functioning elk and bison populations might respond in a natural environment, park managers thought that Yellowstone might be a place to develop this knowledge and resolve the controversy over the size of the herds by letting natural forces regulate the populations. Current laws and regulations give park managers broad discretion on how to manage wildlife in the park. For example, Grand Teton National Park (330,000 acres), just south of Yellowstone (2.2 million acres), has a different mandate, history, neighbors, and geography and has adopted a different policy for managing bison and elk. Grand Teton National Park’s legislation provides for hunting elk within portions of the park and for grazing cattle—two uses that are not allowed in Yellowstone. In addition, critics say that the large elk and bison herds have damaged riparian areas. According to the Park Service’s recently published compilation of 28 reports on research studies of the northern range, Yellowstone’s grasslands do not appear to be overgrazed by any definition of overgrazing. First, bison migrate because they are nomadic. The Controversy Over the Risk of Transmitting Brucellosis From Bison and Elk to Cattle

The extent to which domestic cattle risk infection through exposure to diseased bison and elk—either from mingling directly with infected wild animals or from using rangeland where infected wild animals have previously grazed—is the subject of intense controversy between the Park Service, wildlife management agencies, wildlife conservation groups, livestock interests, Native Americans, and others. Furthermore, although the risk of such transmission has never been quantified, the Park Service maintains that it is likely to be very low. Both Montana and Wyoming officials believe that the vaccines they have used successfully with domestic cattle could be applied to the park’s bison and elk herds. In discussing the controversy surrounding this issue, one official described it as a war. As a result, about 1,100 bison were shot or captured and slaughtered last winter. The goal is to design a plan that will maintain the state’s brucellosis-free classification, reduce damage to private property, and sustain the free-roaming bison and elk herds. Observations

The impact of Yellowstone’s bison and elk herds on the park’s range and riparian areas and the potential for these animals to transmit brucellosis to cattle are highly controversial, sensitive, and emotional issues for the affected parties. This past winter, the slaughter of bison that migrated out of the park, combined with the winter kill, reduced the bison herd to about half of its size the previous year. In the short term, this reduction may limit the migration of bison from the park, relieve some of the immediate pressure on the Park Service to take management actions, and create an opportunity for the Park Service and its critics to complete and assess the results of studies such as the National Academy of Sciences’ review of brucellosis issues.
Why GAO Did This Study

Pursuant to a congressional request, GAO discussed wildlife management issues at Yellowstone National Park, focusing on the: (1) National Park Service's (NPS) current policy for managing free-roaming bison and elk in Yellowstone; (2) controversy surrounding the impact of these herds on the park's rangeland and riparian areas; and (3) controversy surrounding the risks to domestic livestock posed by exposure to diseased bison and elk.

What GAO Found

GAO noted that: (1) current laws and regulations provide park managers with broad discretion on how to manage their park's resources; (2) as a result, parks with similar wildlife resources, such as Yellowstone and neighboring Grand Teton National Park, can apply different approaches to managing these resources; (3) while Yellowstone uses "natural regulation," a policy that allows natural forces to regulate the size of its bison and elk herds, Grand Teton has established specific goals and objectives to control the size of its bison herd; (4) critics of Yellowstone's policy believe that the policy's implementation has produced bison and elk herds that are too large and damage the park; (5) in their view, the park's rangelands are being overgrazed, the riparian areas are being damaged, and because these lands are being depleted, bison and elk are migrating from the park in search of forage on private lands and public grazing areas; (6) according to NPS' recently published studies, however, researchers have found that Yellowstone's grasslands are not overgrazed, and several factors have contributed to the decline of the range and of the riparian areas' woody vegetation; (7) park officials believe that bison are leaving the park for a combination of reasons, because these animals are nomadic by nature, they do not have access to sufficient forage during hard winters, and they can follow snowmobile trails out of the park; (8) the health of Yellowstone's bison and elk herds is a major concern for livestock owners and public officials in the states bordering the park; (9) because many Yellowstone bison and elk are infected with brucellosis, a disease that can cause cattle to abort during pregnancy, these parties fear that the wild animals may transmit the disease to domestic cattle; (10) a state with infected livestock may lose its federal brucellosis-free classification, jeopardizing its right to freely transport cattle across state lines; (11) as a result, these parties believe that the risk of transmitting brucellosis from bison to domestic cattle must be eliminated by containing bison within the park, by using vaccines, or by shooting or capturing bison that leave the park; (12) according to NPS, the risk that brucellosis will be transmitted from either elk or bison to cattle is likely to be very low; (13) this past winter, the Yellowstone bison herd was reduced to about a half of its size the previous year; and (14) in the short term, this reduction may provide an opportunity for NPS and its critics to complete and assess the results of studies which could go a long way toward resolving this controversy.