State and federal agencies, after signing an agreement Wednesday in Montana, will begin tolerating some bison that wander out of Yellowstone National Park to winter range near the north and west entrances.

The agreement stipulates that bison would be allowed to occupy Horse Butte northwest of West Yellowstone, Mont. Earlier this week, Montana officials signed a 20-year, $3.3 million deal that would allow small numbers of bison to use the Royal Teton Ranch to access national forest land out of the park’s North Entrance and avoid slaughter.

Wildlife managers killed roughly 1,600 bison last winter for leaving the park. Officials said the deaths were necessary to prevent the spread of brucellosis to cattle.

Yellowstone spokesman Al Nash said the latest agreement “reflects an important evolution in bison management. But we’re not stopping here. We have many more significant issues to work on, and we will do so.”

Nash said the groups — including Yellowstone National Park, Gallatin National Forest, the U.S. Department of Agriculture, and Montana Fish, Wildlife and Parks — set three goals: to increase tolerance out of the north and west entrances, to conserve a wild and free-ranging bison population, and to prevent the transmission of brucellosis to cattle.

Nash said one impetus for the agreement was a U.S. Government Accountability Office report released in March that criticized the progress of bison management in and around Yellowstone. He said the adaptive management plan sets goals and management responses.

“We have a very clear direction on what may take place, and we have a very definitive means to review whatever this season brings and to learn from it,” he said.

While the agreement wasn’t immediately available Wednesday, attendees at a meeting of the agencies indicated that male bison would be able to inhabit some lands out of the north and west entrances. Females, which researchers think are responsible for spreading brucellosis, would be hazed back into the park by May 15 in most years.

Some conservation groups said the agreement is a step in the right direction for the iconic species, while others said the move doesn’t go far enough to return bison to their natural habitat.

Franz Camenzind, executive director of the Jackson Hole Conservation Alliance, called the management plan an encouraging sign.

“We’re moving in a direction where we’re accepting bison as a part of our native landscape,” he said. “The Horse Butte area, I think, is critical to maintaining the Yellowstone park bison population.”

Camenzind said the Royal Teton Ranch agreement isn’t ideal because it bases bison access on numbers of animals, not the capacity of the landscape. Plus, he said, the deal costs too much money.

“One seems to be a significant step in the right direction and the other is a baby step with very expensive shoes,” he said.

Amy McNamara, national parks program director for the Greater Yellowstone Coalition, also said there is more work to do.

“We need to have a more inclusive discussion about how we truly get to treating bison like wildlife in Montana,” she said.

Stephany Seay, media coordinator for the Buffalo Field Campaign, said her group opposes the Royal Teton Ranch agreement, calling it a “corridor to nowhere.”

The agreement to allow bison on Horse Butte is “definitely not perfect,” she said. “We’re glad to know that, for a few months out of the year, some buffalo won’t be harassed. Horse Butte is cattle-free. It should be year-round habitat.”