A U.S. District Court judge in Billings has rejected the federal government’s request to pause a consolidated lawsuit challenging the 2024 bison management plan for the Greater Yellowstone Area, allowing the legal challenge to move forward.

The Alliance for the Wild Rockies and the Council on Fish & Wildlife filed suit in early January against the National Park Service, arguing that the agency’s approach to managing bison relies on outdated science. The plaintiffs contend that culling bison to address brucellosis—a disease that affects reproduction in cattle, bison, and elk and can sicken humans—targets the wrong wildlife.

About 60% of Yellowstone bison test positive for brucellosis, but only 10% to 15% of infected animals are actually capable of spreading the disease, according to the lawsuit. The plaintiffs cite a 20-year national study concluding that elk, not bison, represent the larger brucellosis problem in the region.

The federal government currently manages approximately 20,000 bison on public lands, with roughly 8,000 unfenced animals roaming outside park boundaries. Yellowstone itself holds about 5,000 unfenced bison, and the park could support up to 10,000 animals. When bison stray beyond the park, federal authorities kill, round up, capture, or haze them.

Mike Garrity, executive director of the Alliance for the Wild Rockies, said the court’s decision represents progress toward science-based management. “The bison management plan is based on outdated assumptions that thousands of bison need to be slaughtered to stop brucellosis infections in cattle,” Garrity stated. “This court decision is a great step in the right direction—we need to base the management of our National Mammal on sound science.”

Montana filed a separate but related lawsuit in 2024 against the federal government over the same bison plan, alleging inadequate state consultation on the management strategy. Since 2010, brucellosis has infected 15 Montana livestock animals.

The federal government’s request to pause the lawsuit would have temporarily halted legal proceedings while the challenge played out, but the judge declined that motion, allowing the underlying case to continue in court.