All bison which had been temporarily held in fenced pastures at the Stephens Creek facility north of Gardiner, Montana, have now been released back into Yellowstone National Park. Some of the nearly 700 bison released had been held in the Stephens Creek Bison Capture Facility since the beginning of February. The release of small groups of bison began the first week in May to see if they would migrate back in to the park. A group of 58 bison plus several newborn calves were also released from the Brogan Bison Facility and were moved back into the park Tuesday. Fifty-three yearling through four-year-old bison remain in the Corwin Springs facility as a part of a USDA Animal and Plant Health Inspection Service initiated research project to determine whether brucellosis positive female bison can be prevented from shedding Brucella bacteria by treating them with a contraceptive vaccine. The National Park Service operates the Stephens Creek Bison Capture Facility northwest of Gardiner, Montana, under the Interagency Bison Management Plan. The Brogan Bison Facility at Corwin Springs, Montana, is operated by the USDA Animal and Plant Health Inspection Service.