YELLOWSTONE NATIONAL PARK, Wyo. — The saucer-sized footprints in the mud around the bloody, disemboweled Bison carcass were unmistakable: wolves.

A pack of 35 named after a nearby snow-dusted promontory, Junction Butte, now were snoozing on a hillside above the carcass. Tourists dressed against the weather watched the pack through spotting scopes from about a mile away.

“Wolves are my main thing. There’s something about their eyes — it’s mystifying,” said Ann Moore, who came from Ohio to fulfill a life-long wish to glimpse the animals.

Such encounters have become daily occurrences in Yellowstone after gray wolves rebounded in parts of the American West with remarkable speed following their reintroduction 25 years ago.

It started with a few dozen wolves brought in crates from Canada to Yellowstone and central Idaho. Others wandered down into northwest Montana. Thriving on big game herds, the population boomed to more than 300 packs comprising some 2,000 wolves, occupying territory that touches six states and stretches from the edge of the Great Plains to the forests of the Pacific Northwest.

Now the 2020 election offers an opportunity to jumpstart the wolf’s expansion southward into the heart of the Rocky Mountains. A Colorado ballot initiative would reintroduce wolves on the state’s Western Slope. It comes after the Trump administration on Thursday lifted protections for wolves across most of the U.S., including Colorado, putting their future in the hands of state wildlife agencies.

Jacob W. Frank, National Park Service via AP file A wolf in the road near Artist Paintpots in Yellowstone National Park, Wyo.

The Colorado effort, if successful, could fill a significant gap in the species’ historical range, creating a bridge between the Northern Rockies gray wolves and Mexican gray wolves in the Southwest.

“Colorado is the mother lode, the final piece,” said Mike Phillips, who led the Yellowstone reintroduction project and now serves in the Montana Senate.

Yet the prospect of wolves is riling Colorado livestock producers, who see them as a threat their forbears vanquished once from the high elevation forests where cattle graze public lands. Hunters worry they’ll decimate herds of Elk and deer.

It’s a replay of animosity a quarter-century ago when federal wildlife officials released the first wolves into Yellowstone. The species had been annihilated across most of the contiguous U.S. in the early 1900s by government-sponsored poisoning, trapping and bounty hunting.

Initiative opponents have seized on s ightings of wolves in recent years in northwestern Colorado as evidence the predator already has arrived and reintroduction isn’t necessary.

“We can live with a few wolves. It’s the massive amount that scares me,” said Janie VanWinkle, a rancher in Mesa County near Grand Junction, Colorado.

VanWinkle’s great grandparents shot wolves on sight up until the early 1940s, she said, when the last wolves in Colorado were killed. The family runs cattle on two promontories with names from that era — Wolf Hill and Dead Horse Point.

But Mesa County’s population has increased more than five-fold since wolves last roamed there, to more than 150,000, and VanWinkle sees little room for the animals among farms and the growing crowds of backcountry recreationists.

“Things have changed,” she said.

The pack that showed up in northwest Colorado last year is believed to have come from the Northern Rockies through Wyoming, where wolves can be killed at will outside the Yellowstone region.

Even under the Endangered Species Act, thousands of wolves were shot over the past two decades for preying on livestock and, more recently, by hunters.

But rancor that long defined the region’s wolf restoration has faded somewhat since protections were lifted in recent years. Opponents were given the chance to legally hunt wolves, while advocates learned state wildlife officials weren’t bent on eliminating the animals.

“I’ve got a simple message: It’s not that bad,” said Yellowstone wolf biologist Doug Smith, who with Phillips brought the first wolves into the park in 1995.

“I got yelled at, at public meetings,” he said. “I got phone calls: ‘They are going to kill all the Elk and deer!’ Where are we 25 years in? We still have Elk and deer.”

On a cold October morning, after examining remains of the Bison eaten by the Junction Butte pack near a park road, Smith said asked a co-worker to have the carcass dragged deeper into brush so it wouldn’t continue attracting wolves and other scavengers that could be hit by a vehicle.

Later, as sun struggled to break through cloud banks, he hiked a trail in the park’s Lamar River valley to where the first wolves from Canada were released.

All around were young stands of aspen trees. The area had been overgrazed by Elk during the years when wolves and most grizzly bears and cougars were absent — evidence, Smith said, of the profound ecological impact from the predators’ return.

Colorado hunting outfitter Dean Billington foresees economic disaster if the 2020 wolf initiative passes. He estimates his firm alone spends more than $250,000 a year for hunting leases on ranches.

“They’re land wealthy and day-to-day poor,” Billington said of ranch owners. “This income keeps the western ranching guys afloat.”

The initiative calls for initially introducing 10 wolves annually by Dec. 31, 2023, with a goal of 250 wolves within a decade.

Rob Edward with the Rocky Mountain Wolf Action Fund, the group behind the initiative, sees reintroduction as a national rather than state issue since it involves public lands that account for 70% of western Colorado.

“Colorado’s public lands are diminished without wolves,” he said.

The Yellowstone experience is key to his group’s arguments: Reintroduction restores balance to the ecosystem, improves wildlife habitat and will benefit hunters by thinning weaker prey.

Standing in the pen where Yellowstone’s wolves got their start, Smith said that if the Colorado initiative passes, success ultimately rests more on human tolerance than the animals’ proven biological resiliency.

“Don’t recover wolves unless there’s areas where you can leave them alone,” he said.