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.

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.