U.S. National Park Service

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Expected conflicts between wolves and humans and the amount of time required of park officials to manage a wolf population are among reasons the National Park Service hasn’t reintroduced the animal to control the elk population at Rocky Mountain National Park. Park staff and volunteers shoot excess elk instead. (Associated Press)

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In this Friday, June 15, 2012 photo provided by the National Park Service, climbers hike through the area where an avalanche swept a Japanese climbing team off a hill during their descent from Alaska's Mount McKinley. U.S. National Park Service officials say five people were traveling as a one rope team early Thursday morning as part of a Miyagi Workers Alpine Federation expedition on the Alaska mountain. The NPS said Hitoshi Ogi, 69, survived after falling 60 feet (18 meters) into a crevasse. He was able to climb out. The other four tumbled into the avalanche debris and haven't been seen since. (AP Photo/National Park Service, Kevin Wright)

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As the sun rises over the Tidal Basin, Cory Cain, a tree worker with the National Park Service trims dead branches as the cherry blossoms make an early arrival with their pink and white blossoms in Washington, D.C., Thursday, March 15, 2012. (Rod Lamkey Jr./The Washington Times)

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As the sun rises over the Tidal Basin, Cory Cain, a tree worker with the National Park Service trims dead branches from a cherry tree as the cherry blossoms make an early arrival in Washington, D.C., Thursday, March 15, 2012. (Rod Lamkey Jr/The Washington Times)

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The firefall from Glacier Point in Yosemite National Park presents itself as a molten lava flow at sunset in mid-February when the sun and Earth align to create a fleeting phenomenon and winter weather cooperates. (National Park Service via Associated Press)

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Occupy DC protesters cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square with a large blue tarp at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Park Police officers Lt. Steve Godfrey, left, and Sgt. Todd Reid are followed by Occupy DC protesters after they check out a large blue tarp which protesters used to cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Occupy DC protesters cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square with a large blue tarp at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Occupy DC protesters Christopher Seerden of Santa Cruz, Calif., left, and Sean Maupin, right, of Lawrence, KA yell and dance after protesters cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square with a large blue tarp, right, at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Occupy DC protesters cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square, top center, with a large blue tarp at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Occupy DC protesters cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square with a large blue tarp at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Joseph Moehrle of Fredrick, Md. wears a gas mask and waves a United States flag after protesters cover the statue of Maj. Gen. James B. McPherson in the center of McPherson Square with a large blue tarp at noon on the day of a deadline the National Park Service set to remove camping material from McPherson Square and Freedom Plaza, Washington, DC, Monday, January 30, 2012. (Andrew Harnik / The Washington Times)

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Occupy D.C. protesters cover the statue of Major Gen. James McPherson in the center of McPherson Square with a large blue tarp at noon on Monday, Jan. 30, 2012 — the deadline the National Park Service set to remove camping material from the square and from Freedom Plaza in Washington. (Andrew Harnik/The Washington Times)

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Occupy D.C. protesters cover the statue of Major Gen. James McPherson in the center of McPherson Square with a large blue tarp at noon on Monday, Jan. 30, 2012 — the deadline the National Park Service set to remove camping material from the square and from Freedom Plaza in Washington. (Andrew Harnik/The Washington Times)

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Occupy D.C. protesters cover the statue of Major Gen. James McPherson in the center of McPherson Square with a large blue tarp at noon on Monday, Jan. 30, 2012 — the deadline the National Park Service set to remove camping material from the square and from Freedom Plaza in Washington. (Andrew Harnik/The Washington Times)

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Tents still remain throughout McPherson Square less than an hour before the deadline set by the National Park Service for Occupy D.C. protesters to remove camping material from the square and Freedom Plaza in Washington on Monday, Jan. 30, 2012. (Andrew Harnik/The Washington Times)

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Jonathan Jarvis, director of the National Park Service, testified the Park Service will soon begin a crackdown on Occupy D.C. campers. (Andrew Harnik/The Washington Times)

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The west entrance to Mount Rainier National Park in Washington state is seen on Jan. 1, 2012. State patrol troopers were checking outgoing cars and park rangers were turning away visitors after a National Park Service ranger was shot and killed that morning. (Associated Press)