CORWIN SPRINGS, Mont. – For the first time since the 1800s, a small group of wild bison were herded Wednesday through fresh-fallen snow to reach their historical grazing grounds north of Yellowstone National Park.

As pronghorn antelope and mule deer scattered to avoid the procession, park employees and state livestock agents on horseback pushed the 25 bison about 10 miles down the Yellowstone River valley. It took about three hours to reach an open meadow in the Gallatin National Forest, where the animals will be allowed to remain until spring.

The move could provide at least some relief from government-sponsored mass slaughters of the iconic Western animals, often called buffalo. Past winter journeys by bison seeking to graze at lower elevations have been blocked over fears that a disease carried by some could infect cattle.

During the last major migration, in 2008, 1,600 Yellowstone bison were killed – about a third of the park’s total.

Yet progress toward ending the slaughters remains tenuous. Deep snow in Yellowstone’s interior has set the stage for another major migration this year, meaning hundreds of bison could yet be captured and killed.

“It seems like the progress is slow, but it’s slow because it’s so complex,” said Colin Campbell, Yellowstone’s acting superintendent. “In all reality, there will always be limits, like there are with any wildlife species.”

Wildlife officials said the Forest Service land where the 25 bison will be allowed to roam is roughly 2,500 acres, or less than four square miles. If this year’s “test” operation goes well, the number of bison allowed eventually could be increased to 100.

Access to the land came at a steep price: Government agencies and private conservation groups paid more than $3 million to establish a bison travel corridor through the Royal Teton Ranch, a sprawling property just north of Yellowstone owned by the Church Universal and Triumphant.

Electrified fencing now lines the dirt road that passes through the ranch – a reminder that the newfound tolerance for bison in Montana has its limits. Critics dubbed the route the “corridor to nowhere” because bison that attempt to migrate much farther will be turned back or killed.

One bison advocate watching Wednesday’s herding operation warned that it would establish a scent trail other bison could follow to their doom.

“You can’t treat bison like livestock. This is a wild animal and they’ve set up a livestock operation” said Stephany Seay with the Buffalo Field Campaign.

To keep close tabs on the animals, they received ear tags, radio collars and, for females, tracking devices implanted in their vaginas in case they abort their young. The disease some bison carry – brucellosis – can cause animals to prematurely abort. No bison-to-cattle transmissions have been recorded.

A 2000 agreement committed federal and state officials to pursue more room for the animals to roam in Montana. But its successes have been few and 3,800 bison have since been killed.