BOZEMAN, Mont. — Yellowstone National Park officials say rangers arrested two people who were trying to chain themselves to a corral where wild bison are held.

Park spokeswoman Vicki Regula said rangers made the arrests early Tuesday. She declined to identify them or say whether they were being detained or charged.

The Bozeman Daily Chronicle reported the people arrested are affiliated with an advocacy group called Wild Buffalo Defense and seek to draw attention to the slaughter of bison.

Some bison that migrate out of Yellowstone during the winter are captured for slaughter or held in quarantine for possible relocation to Native American reservations. This year’s capture began Feb. 16.

Tuesday’s arrests marked the third time this winter that people have attempted to interfere with the holding pens.

More than 50 bison escaped from the Stephens Creek holding facility Jan. 16 after someone cut through a fence. Most of the animals, which were set to be transferred to the Fort Peck Tribes in northeastern Montana, were later found in the Mammoth Hot Springs area. The Park Service did not plan to recapture the bison unless they returned to the holding facility on their own.

One month later, 73 animals escaped after pens at Stephens Creek were again tampered with. Most of them eventually returned via the fence openings they had escaped through.

Montana has limited tolerance for natural bison migrations from the park due to fears about spread of brucellosis, a disease that can cause pregnant cattle to miscarry. Brucellosis is also carried by free-roaming elk in the region.

Federal and state agencies responsible for managing bison that migrate out of the park plan to cull 600 to 900 animals this winter through hunting and slaughter.

About 4,800 bison live in the park.

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