A wolf-advocacy group said it will sue Rocky Mountain National Park over its decision to hire sharpshooters to kill up to 200 elk a year at the park as a way to handle overpopulation.

The decision to use the sharpshooters was made in December but signed Friday by Mike Snyder, intermountain director for the National Park Service.

A WildEarth Guardians officer said Monday that federal officials didn't take a fair look at introducing wolves to the park as an alternate way to keep the elk population down.

Elk - there are an estimated 2,000 in the park - are destroying aspen and willows in large stretches on the eastern part of the Continental Divide, threatening to decimate large areas of the riverbank ecosystem.

The Park Service says shooting elk will be part of a plan that also includes fences, restoring trees and redistributing the elk.

But Rob Edward, director for carnivore recovery for the Santa Fe, N.M.-based WildEarth Guardians, said 30 or 40 wolves could accomplish the same goals in a more natural way.

"We need to have enough wolves in the park that they're having an effect on the movement of elk through the landscape," Edward said.

That would mean two or three packs, he said.

A wolf needs 7-1/2 pounds of meat a day, so each pack likely would take down an elk every three days, Edward said.

The problem isn't so much that there are too many elk in the park but that there are no predators forcing them to move throughout the park, he said.

With no incentive to move, the elk chew the aspen and willows down to the roots, wiping out entire stretches of the trees that are essential to the ecosystem.

Wolves would get the elk moving from one willow patch to another.

Edward said the White House is hurting the cause of wolves on two fronts. In the areas where they've been reintroduced and are thriving, the Bush administration wants to take them off the endangered-species list.

On the other hand, the administration is dragging its feet on reintroducing wolves to areas where they formerly ranged, such as Rocky Mountain National Park, he said.

Yellowstone National Park reintroduced wolves in 1995. A decade later, there are probably hundreds of wolves there, and the willows are dramatically healthier, Edward said.

National Park Service officials haven't ruled out introducing wolves to the park as a way to deal with the problem, they said, but that will not be among the first solutions tried. They said the state of Colorado doesn't support reintroduction of wolves "at this time."

The plan relies on the gradual shooting of elk rather than intense culling, as had been proposed in one of the draft plans, Park officials noted.

Healthy carcasses of the downed elk would be donated to groups in need.

Large winter storms the past few years have killed some of the elk, reducing their population from the 2001 peak, so there likely isn't an immediate need to shoot many of the animals.

The National Park Service plan also calls for testing live elk for chronic wasting disease.

In the first year, up to 120 female elk would be captured, be tested for the disease and be given a fertility-control treatment. Biologists hope they'll learn new and better ways to deal with CWD by testing the female elk.

Any elk that tested positive for CWD - a relative to "mad cow" disease - would be killed and removed.

The final plan "balances the most important management issues with the many differing viewpoints expressed," said Park Service Superintendent Vaughn Baker. It will be the guideline for managing elk for the next 20 years.