YELLOWSTONE NATIONAL PARK — The National Park Service (NPS) announced its decision on a new plan for the future management of bison in Yellowstone National Park (YNP) July 24. As part of the plan, the existing target bison population of 3,000 has been updated to a range of 3,500 to 6,000.
NPS was required to update its Interagency Bison Management Plan, drawn up in 2000, following a 2018 lawsuit by a Montana-based conservation group arguing that that plan was out of date and posed a danger to the public.
In response to court requirements following the litigation, NPS developed a final Environmental Impact Statement on its updated management plan, unveiled in June. The statement offered three options, each of which had different population targets and emphasis on different population management programs. The chosen alternative sets the new population range at a cap of 6,000 and puts an “emphasis on using the Bison Conservation Transfer Program to restore bison to Tribal lands and Tribal treaty harvest, and public hunting outside the park to regulate numbers.”
Managing the bison population in the park is a delicate dance, with competing interests from ranchers outside the park, hunters outside the park, area tribes, the Yellowstone ecosystem and visitor enjoyment to take into account.
“We have taken into consideration that there are a lot of people divided on what the population level should be,” Cam Sholly, Superintendent of YNP, told Buckrail. “We’ve selected a population range that we feel achieves multiple objectives.”
The new decision is based on years of following and managing the bison population in the park.
“A lot of this is solidifying the work that’s been done over the past couple decades,” Sholly said.
Another factor in the new plan is brucellosis transmission. An estimated 60% of female bison in the park test positive for the Brucella abortus bacteria, which can cause abortions in its hosts. While there has not been a documented case of brucellosis transferred from bison to cattle, the new plan takes into consideration that larger bison herds could could lead to transmission between bison and cattle.
“If we let the population grow too high, and if bison started to interface with cattle, then there would be likely brucellosis transmission between bison and cattle,” Sholly says. “Given the limited amount of tolerance because of brucellosis concerns by the state of Montana primarily and ranchers, we have selected a lower level alternative.”
Yellowstone is the only place in the lower 48 states where bison, the largest land-dwelling mammal, have lived continuously since prehistoric times. The current population is the largest on public land. In 2024, the pre-calving population was estimated at 4,550.
