The National Park Service announced in July a decision about the future management of bison at Yellowstone National Park, a culmination of an Environmental Impact Statement (EIS) and National Environmental Policy Act process that began in 2022 and will allow the Park Service to manage bison based on “new scientific information and circumstances that have changed since the previous EIS, completed in 2000.”

Recent research has concluded brucellosis transmission to livestock — a concern that has underpinned the park’s bison-management approach for more than two decades — is more likely attributable to elk than bison.

The U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service, in tracing the genetic lineage of brucella across the ecosystem and among species, say elk are now recognized as a primary host for brucellosis and have been found to be the major transmitter of B. abortus to cattle, according to the National Institute of Health.

“All recent cases of brucellosis in [greater Yellowstone area] cattle are traceable genetically and epidemiologically to transmission from elk, not bison. This is one of the most significant changes in our understanding of brucellosis epidemiology in the GYA since 1998,” according to results announced by the Coordinating Council for the National Animal Health Laboratory Network. The council is led by the USDA and includes representatives from state departments of agriculture and national and state laboratories.

The National Park Service was also under court oversight to complete this decision due to litigation in 2018 and 2019 that challenged the adequacy of the original Interagency Bison Management Plan 2000 decision.

Bison are managed differently from other wildlife because Greater Yellowstone Ecosystem states have limited tolerance for bison migrating out of the park.

The published decision identifies the actions the park will take to manage bison within Yellowstone. It also sets conditions over how the park will support its partners in their efforts outside of Yellowstone as multiple federal, state, and tribal entities have some authority over managing bison as they migrate out of the park.

"We have come a very long way since the last bison management plan was signed in 2000," said Superintendent Cam Sholly in a July 24 press release. "This new plan solidifies much of the progress made over the past two decades and provides a foundation for future decision making. We appreciate the significant engagement on this plan by our affiliated tribes, partners, and the general public."

The decision continues the original purpose of the bison management plan to maintain a wild, free ranging bison population and reduce the risk of brucellosis transmission from bison to cattle.

Through this decision, the park will prioritize working with American Indian tribes to transfer brucellosis-free bison to tribal lands and use harvests to control bison numbers to the extent feasible. The population range protects the genetic integrity of the species and the important role bison play in the ecological balance of the park. It also preserves an ecologically sustainable population of wild, migratory bison.

Public feedback played a key role in the decision. During the 2023 public comment period, more than 27,000 comments were received on the draft Environmental Impact Statement.

For more information about bison management plans: parkplanning.nps.gov/projectHome.cfm?projectId=94496.