Perhaps sensing a drastic change in the weather, roughly 300 bison left Yellowstone National Park during the weekend and headed to lower ground in Montana, where they were met Monday by hazers who forced them back into the park and into a "capture facility."

The bison movement came as a cold front barreled south out of Canada and draped sub-zero temperatures across the park. Monday's high temperature was in the single digits, the overnight low was forecast to plunge to 28 below zero, and Tuesday's high wasn't even expected to reach zero degrees Fahrenheit.

The bison had moved nearly 10 miles and onto private and public land north of Corwin Springs during the weekend. By late Monday afternoon "approximately 300 bison was hazed into the Stephens Creek bison capture facility," federal wildlife managers said in a prepared statement. The facility, located inside the northern boundary of Yellowstone just northwest of Gardiner, Montana, is operated under the Interagency Bison Management Plan.

Under that plan, when hazing bison back into the park "becomes unsafe or ineffective, bison can be captured at the Stephens Creek capture facility," a release from the park said.

Migrating bison, genetically programmed to head to lower ground in winter, long have been viewed as a problem at Yellowstone. Montana livestock officials, worried their state might lose its "brucellosis-free status" and thus require expensive testing of their cattle herds to ensure they don't carry the disease that can cause spontaneous abortions in livestock, have long been opposed to letting Yellowstone bison wander out of the park and into their state.

Earlier this year, though, there was an effort to see if some "tolerance" couldn't be developed among those livestock interests by allowing a small number of bison to move out of the park and north into the Gallatin National Forest. However, wildlife managers and livestock agents have had trouble keeping the bison on the forest lands and away from private lands. One bison was shot and killed last week when efforts to haze it back onto the national forest failed.

The latest foray of several hundred bison out of the park and into Montana this past weekend could further exasperate the efforts to build tolerance in the state to roaming bison.

Since a large number of bison were discovered well north of the park boundary again Monday morning, the IBMP partners made the decision to haze them into the capture facility.

The partner agencies have agreed at this point in the winter that captured bison will be tested for exposure to brucellosis, that seropositive bison will be shipped to slaughter, and that they endeavor to hold seronegative bison for spring release back into the park. Meat from bison shipped to slaughter will be distributed to tribal groups and regional food banks.

The IBMP partners are looking for opportunities to alleviate the need to hold and ship bison to slaughter this winter. Looking beyond this winter, they will also continue discussions for the long-term on how and where Yellowstone bison might be tolerated in areas surrounding the park or relocated outside of the park if captured.

To-date, no bison have been shipped to slaughter during the winter of 2010-2011. State permitted and tribal hunters have taken approximately 90-110 bison this season. Three bison have been killed due to management actions. The late summer 2010 population estimate was 3,900 bison.

For safety reasons, the area around the Stephens Creek facility is closed to the public when capturing, holding, and releasing bison. A map and information on the closure is available for public review during normal business hours at Mammoth Hot Springs in Yellowstone National Park at the Albright Visitor Center and the Office of the Chief Ranger.

This is the eleventh winter the IBMP has been used to guide brucellosis risk management actions.

The cooperating agencies operating under the IBMP are the National Park Service, the U.S. Forest Service, the Animal and Plant Health Inspection Service, the Montana Department of Livestock, the Montana Department of Fish, Wildlife and Parks, the InterTribal Buffalo Council, the Confederated Salish Kootenai Tribes, and the Nez Perce Tribe.

More information on the IBMP can be found at http://ibmp.info/.