FLAGSTAFF, Ariz. — The National Park Service is looking at using sharpshooters, capture and other methods to reduce the number of bison that are roaming the far northern reaches of the Grand Canyon and damaging resources, officials said.

The massive animals can weigh up to 2,000 pounds, and park officials say they are destroying water sources, vegetation, soil and archaeological sites.

Hunting is prohibited within park boundaries, but the agency has the authority to kill animals that harm resources, using park staff or volunteer hunters.

The Park Service announced in 2014 that it would work on a long-term plan to manage bison and do a more in-depth environmental review.

But the Grand Canyon said last week that it changed course because immediate action is needed to control the bison.

Park officials are asking the public for comment. Between 80 and 200 bison are sustainable, not the 400 to 600 living on about 310 square miles, officials said.

“We're considering a suite of tools,” Sue Consolo-Murphy, acting chief of science and resource management, said Friday. “Until we get into this, we don't know what's going to work.”

Identical bills in the U.S. House and Senate would let state-licensed hunters kill the bison and keep the meat. Arizona Sen. John McCain and Rep. Paul Gosar touted them as a cost-saving measure and criticized the Park Service for what they see as delayed action.

“We have a plan, and it puts Arizona hunters to work doing what they love, accomplishing this important task for free,” Gosar said last week.

Consolo-Murphy said the park is looking at models in other places for shrinking wildlife populations.