BILLINGS, Mont. (AP) — Five bull bison from Yellowstone National park have been transferred to an American Indian reservation in northwest Montana under an effort to bolster herds of the animals outside the park.

The animals were released into corrals on the Fort Peck Reservation on Friday. They'll be under quarantine for the next year to ensure they are free of the disease brucellosis.

Thousands of Yellowstone bison trying to migrate outside the park have been sent to slaughter in recent decades to shield domestic livestock from potential brucellosis infection.

The five bulls transferred to the Assiniboine and Sioux tribes had been tested repeatedly for the disease.

About 80 bison remain under quarantine at Yellowstone and more are being held at a nearby U.S. Agriculture facility.

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