"Elk like to eat. Elk like to eat a lot.

This is a problem for creatures fond of the same greenery coveted by the weighty elk. It is not so good for the ecosystem, either, according to the stewards of three national parks in Colorado and the Dakotas that are faced with growing herds of the herbivorous mammals.

Scientists at Theodore Roosevelt National Park in North Dakota are preparing to do an elk count, sending an airplane aloft after a fresh snow, when it is easier to spot the quarry in rugged terrain.

"Based on last year's survey, we expect to see a thousand or so elk," said Bill Whitworth, the park's chief of resource management. "We'd like to have somewhere between 100 and 400. We're balancing our elk population with bison, feral horses, other deer and animals that use the forage out here."

Reducing elk herds is not a gentle business. The National Park Service mostly figures on shooting elk, either on parkland using staff members and designated deputies, or on private land where hunters can load up.

Nature in the form of drought or severe snow sometimes helps. It used to be that elk could be shipped elsewhere, but the surfeit of elk and the rise of chronic wasting disease made that option less attractive. In Rocky Mountain National Park in Colorado, 60 female elk, called cows, were injected with a contraceptive designed to be effective for several years.

Spokeswoman Kyle Patterson said proposals to curb the elk population at Rocky Mountain have inspired "strong feelings across the board." Recommendations ranged from shooting and fencing to contraception and the introduction of wolves, one of elk's few natural predators.

Park managers settled on "lethal reduction," as shooting is called, as the preferred way to control the herd. Sharpshooters with night-vision goggles and silencers would target elk after dark. A formal decision is expected to be released soon, Patterson said, with the program likely to begin next winter and continue for two decades.

"This is a 20-year plan that we've been working on," Patterson said, explaining that the elk population will be monitored through fat times and thin. "Willow and aspen stands are declining. That's what we're concerned about, because that deprives other species of habitat they need.

"We have to manage for the others . . . beaver, butterfly, a variety of birds, insects," Patterson continued. "It's a whole ecosystem concept, and it can get out of whack."

The 415-square-mile park has a winter elk population between 1,700 and 2,200. The park's goal is 1,600 to 2,100 elk, down nearly half from highs reached as recently as 2001.

Since then, unusually deep snow in March 2003 and December 2006 motivated the elk to migrate to more hospitable climes at lower elevations outside the park, Patterson said. Last year, she noted, hunts supervised by the Colorado Division of Wildlife culled 750 elk outside the park.

"We have to plan for some of those things not happening," Patterson said. "If they do, we would cull fewer animals."

A conservation group called WildEarth Guardians opposes shooting elk, preferring the introduction of wolves, which helped control the elk population in Yellowstone National Park -- more than eight times larger than Rocky Mountain -- beginning in the mid-1990s. The organization has threatened to file a lawsuit.

Bryan Richards, who studies elk for the U.S. Geological Survey, said the combination of healthy habitat and few predators is likely to create a continuing elk problem for Rocky Mountain, Theodore Roosevelt and South Dakota's Wind Cave National Park. Human intervention is a necessity, he said.

"Unfortunately, with the hand of cards that has been dealt to the Park Service, there aren't any clear-cut great answers," he said. "If there are not tools implemented to keep those populations in check, the populations will spiral out of control."

Steve Torbit, Colorado-based regional director for the National Wildlife Federation, sees lessons for the future in the elk conundrum. He said the nation is "paying the price for these smaller parks that do not allow for the animal herds to have seasonal movement."

When parks expand, or new parks are created, Torbit says, they should include buffer zones where hunting and wildlife management are permitted "and you don't build the subdivisions or the ranches right up against the park boundary."" (Peter Slevin, The Washington Post, February 11, 2008)

Staff writer Kari Lydersen contributed to this report.