A coalition of environmental and Native American groups sued two federal agencies Monday to stop the mass slaughter of bison that migrate outside Yellowstone National Park in search of food.
During the last decade, federal agencies working with the state of Montana have captured and shipped to slaughter more than 3,300 bison to prevent the spread of an animal disease to cattle.
The lawsuit asks a U.S. District Court judge to bar the National Park Service and Forest Service from participating in the slaughter program.
The plaintiffs contend the two federal agencies are ignoring their responsibility to preserve the animals. It also says the threat of the disease, brucellosis, has been overstated.
"It's crazy for me to think that in a state like Montana, where we are rich in wildlife and wildlands, that we don't have room for bison," said Tom Woodbury with the Western Watersheds Project.
Woodbury's group is one of nine plaintiffs in the case, which is likely to be heard by Judge Donald Molloy in Missoula.
Yellowstone's 3,000 bison comprise one of the largest concentrations of the animals in the world. Bison once roamed North America by the millions before being largely wiped out in the late 1800s.
Today about half the animals in the park test positive for exposure to brucellosis, a reproductive disease that can cause pregnant animals, including cattle, to abort their calves.
During severe winters and when bison numbers are high, thousands of the animals try to migrate to lower elevations outside Yellowstone in search of grass for grazing. But under a 2000 agreement between Montana and the federal government, the animals can be killed to prevent any contact with cattle.
In early 2008, when the bison population had topped 4,000 animals, more than 1,400 bison were captured and shipped to slaughter.
That same year, the Government Accountability Office released a scathing report admonishing federal agencies for failing to preserve Yellowstone's bison.
As a result, state and federal wildlife managers promised to be more flexible on the issue.
They've since allowed some bison to linger outside the park in areas where cattle no longer graze. And last year, with financial backing from several conservation groups, the agencies leased a corridor through a private ranch adjacent to Yellowstone, allowing a small number of bison to access Forest Service land outside the park.
Federal officials said they were keen to expand where bison could go - but not at the expense of raising risks of brucellosis transmission.
"We need to learn from those baby steps to see if we might apply those at a broader scale," said Forest Service spokeswoman Marna Daley with the Gallatin National Forest.
Bison control used to be carried out largely by the Montana Department of Livestock. Under the 2000 agreement, management of the animals has been coordinated by a group of five federal and state agencies, including the Forest and Park services.
What additional steps might be taken by those agencies is unclear. Yellowstone spokesman Al Nash said the park is committed to an environmental study looking at the potential for vaccinating bison against brucellosis, but he could not offer a timeline.
Brucellosis first came into the Yellowstone region through the cattle of early by European settlers. It has since been eliminated in the livestock industry and is now found only in Yellowstone's wildlife.
Elk also carry brucellosis and are considered the likely culprits in at least seven transmissions to cattle over the last decade.
However, the Yellowstone region's estimated 100,000 elk are not subject to a slaughter policy. That's largely because they are more difficult to track and are found over a far wider range.