BILLINGS - Montana livestock agents plan a major push over the next week to haze several hundred wild bison back into Yellowstone National Park to protect area cattle ranches from disease.
Helicopters, all-terrain vehicles and horseback riders will attempt to drive about 400 animals into the park. The bison had exited Yellowstone over the winter in search of food at lower elevations.
Critics say the hazing is unnecessary, particularly in areas where cattle no longer graze.
But facing pressure from the ranching industry, Montana officials said they plan to remove all bison from public and private lands around West Yellowstone by May 15. That's about a month before cattle will return to their summer grazing plots.
Whether the bison cooperate remains to be seen: Late spring snowstorms have stalled the emergence of grasses inside Yellowstone that bison depend on for forage.
The park's chief ranger, Tim Reid, said the delayed "greenup" of Yellowstone could complicate the hazing effort unless warm weather sets in quickly. Reid said if conditions are not right, bison hazed into the park could simply circle around and leave again.
The animal disease brucellosis can cause infected animals to abort their young. It has been eradicated nationwide except for the Yellowstone region. About half of Yellowstone's bison test positive for exposure, although the rate of active infections is much lower.
If the disease shows up in cattle, ranchers can face costly export restrictions when trying to sell their livestock. The states surrounding Yellowstone - Montana, Idaho and Wyoming - have all suffered cattle infections over the last decade.
However, in each case, the infections were later linked by veterinarians to diseased elk, not bison. There has never been a recorded bison-to-cattle transmission in the wild.
Limited bison hazing operations were launched in the West Yellowstone area on May 4, but were frustrated by a spring storm.
"They're always trying to fight mother nature instead of working in harmony with it," said Mike Mease with the Buffalo Field Campaign, a group opposed to the hazing. "As long as the cattle industry is still not giving an inch on their drop dead date, we're going to continue running into problems."
To complete the hazing effort, state livestock agents and Yellowstone personnel plan to push the animals into the park in stages.
Bison already in Yellowstone would be pushed deeper into the park, making room for more as those animals are pushed out of Montana, said Department of Livestock spokesman Steve Merritt.
"It's always a challenge, but we think we're set for success," said the agency's executive officer, Christian Mackay.
State and federal officials have conducted similar bison hazings for the last decade under a cooperative agreement. In recent years, the agencies at times allowed bison to linger outside the park well past the May 15 deadline.
That included bison on a narrow peninsula surrounded by Hebgen Lake, an area known as Horse Butte. Bison have become a springtime fixture on the peninsula since a cattle ranch there was retired several years ago.
The Department of Livestock returned to a definitive May 15 deadline two years ago in response to a lawsuit filed by Yellowstone area cattle ranchers backed by the Montana Stockgrowers Association.
The suit seeks to strip state and federal agencies of flexibility in deciding when bison need to be moved. It remains pending before state District Judge John Brown in Gallatin County.
Jim Brown, the ranchers' Helena-based attorney, said brucellosis remains a threat even with cattle now gone from some areas outside the park.
"If we didn't believe there was an immediate threat of transmission, we wouldn't have filed the suit," he said.
Bison have been known to swim from the Horse Butte peninsula to areas where cattle grazing continues. Nine animals made the crossing last week before they were hazed onto the Gallatin National Forest.