MEEKER, Colo. — Colorado's former big game manager, John Ellenberger, remembers when the Piceance Basin was called the state's mule-deer factory because of its tens of thousands of deer.

The 7,110-square-mile basin, about 170 miles west of Denver and dissected by the Colorado River, boasts some of the largest deer and elk herds in the country.

Now Ellenberger wonders if Colorado can keep those bragging rights. During a recent tour of the basin, 18-wheelers barreled down a county road as companies drill holes and lay pipes for natural gas in what has become one of the nation's energy hot spots. "You definitely get this feeling of being in the middle of an industrial zone," he said.

Throughout the Rockies — the Pinedale Anticline of northwestern Wyoming, the Powder River Basin in northeastern Wyoming and southern Montana — the energy boom is changing a once-pristine landscape. It's generating lawsuits, regulatory fights and heated public relations battles between those championing America's untapped energy potential and those worried about populations of deer, elk, pronghorns and sage grouse.

"I think we're watching the end of the West," said Steve Torbit, regional executive director of the National Wildlife Federation. "We'll have post-stamp areas like Rocky Mountain National Park and Yellowstone and Zion National Park. The rest is going to be industrial-scale productions."

Colorado has 35,440 active wells and last year issued 6,368 drilling permits, most for natural gas. There are 1,844 producing oil and gas wells on federal land in the Piceance Basin, which holds an estimated 115 trillion cubic feet of natural gas. By 2028, there could be 2,000 well pads on federal and private land in the basin, with a rough average of eight wells per pad, said Jim Sample of the U.S. Bureau of Land Management in Lakewood.

With the record drilling, Colorado is rewriting its oil and gas regulations to give more weight to wildlife, the environment and public health when issuing drilling permits.

The industry insists it shares concerns for wildlife. "Our employees live and work here and love this state and its precious natural resources as much as anyone," said Howard Boigon, an attorney representing Bill Barrett Corp., recently told the Colorado Oil and Gas Conservation Commission.

But there must be a balance, given rising energy prices and the push to cut dependency on foreign oil, Boigon said. Trade groups argue that proposals to shield wildlife in mating and birthing seasons would shut down drilling in western Colorado for long stretches each year.

An ad campaign by the Colorado Oil and Gas Association and the Colorado Petroleum Association warns that will throw thousands of people out of work.

A similar fight is in Wyoming, where the Theodore Roosevelt Conservation Partnership is suing the federal government to force more wildlife protection in the northwestern part of the state. The group wants more restrictions on energy development throughout the West to protect the sage grouse, which is under being considered for the federal endangered species list.

Before the rules debate, the flash point in Colorado was the Roan Plateau, which rises about 3,000 feet over the Colorado River in the Piceance Basin. In August, the BLM plans to offer oil and gas leases on about 55,000 acres of public land on the Roan.

Acknowledging the importance of the Roan as wildlife habitat, some observers believe the rest of the Piceance has been overlooked.

Jeff Madison, a former state wildlife biologist who's now the natural resources specialist for Rio Blanco County, said the north end of the Piceance Basin has wild places rivaling the Roan Plateau. The area boasts hills studded with piñons and juniper trees, towering wooded peaks and sagebrush-covered high plains.

"I describe it as a decoy almost. All the concentration has been on the Roan and all the resources on the Roan, and that's legitimate," Madison said. "But it's a fraction of what we stand to lose out here."

Hunting, fishing, recreation and tourism sustained many western Colorado communities through the energy bust of the 1980s and beyond. A 2004 report commissioned by the Colorado Division of Wildlife estimated that hunting and angling generate $1.5 billion in economic benefits for the state and support 20,000 full-time jobs.

Industry officials note the tens of thousands of jobs and nearly $23 billion in economic benefits attributed to oil and gas in a 2007 state-funded study. They say studies in Wyoming showing that development hurts sage grouse, and deer don't necessarily transfer to Colorado because of different terrain.

But Ellenberger, Colorado's former big game manager, said there's no question that wildlife will be affected. "If we want to have wildlife resource and habitat that are still here after development occurs, then let's proceed in a careful fashion," he said.