– Only buffalo break the horizon. Points of shiny black horns glint in the sun. Tails switch at flies. Hoofs set dust swirling. The animals rise from a sea of rippling bromegrass, timothy and Kentucky bluegrass.

Hundreds of years ago, the scene might have stretched for hundreds of miles. Today, it runs to the Blue Mounds State Park boundary.

“It’s easy to stand out here, especially in that tall grass, and think about what that would’ve been like,” park manager Chris Ingebretsen says. “There’s places here you can hide the surrounding modern-day landscape pretty easily. Add the wind that is constant and the sound of the meadowlarks and the grunt of the bison.”

In one direction, the scene ends in cornfields outside Luverne, which is outlined on the horizon. At the observation platform near park headquarters, it ends where three rental teepees stand. Across U.S. Hwy. 75, it ends in a farmer’s pasture of buffalo.

For the buffalo, it nearly ended altogether.

The North American population was an estimated 45 million before Europeans moved in and hunted them to near extinction. It dwindled to fewer than 1,000 by the end of the 19th century.

Today, the herd that roams 540 acres of Blue Mounds’ fenced prairie is about 100. Because tall grass conceals the calves, the exact number is a surprise until the September roundup.

At the annual roundup, the herd is thinned and animals sold — mostly to bison producers. Since 2012, workers have collected hair and blood samples, which are sent to Texas A&M University for genetic testing. Turns out the Blue Mounds buffalo are central to a statewide conservation effort with connections that range far beyond Minnesota’s borders.

Only by accident did the Blue Mounds herd remain free of cattle genetics.

The discovery came about when Texas A&M was testing federal herds, and the Minnesota Zoo wanted to focus on bison conservation. The tests revealed cattle DNA was present in all but 1 percent of bison tested in the U.S.

“We breed tigers, leopards, we breed rare species around the world. That’s where we put our resources. Then we found out about the plight of the bison,” said Tony Fisher, director of animal collections. “The zoo could help preserve the species in its pure form.”

Pure bison herds had been preserved at Yellowstone National Park and the Bronx Zoo. But the species survived because prominent ranchers crossed them with cattle.

“If that wouldn’t have happened, you wouldn’t have bison today. The Yellowstone numbers that were preserved back in the 1910s and ’20s wouldn’t have been enough to carry the herd,” Ingebretsen said. “[Ranchers’] efforts were a mixture of caring and a mixture of economy.”

They never did produce the hoped-for superior beef animal that could withstand harsh winters.The cattle crosses look like pure bison, but Fisher said they’re smaller and less thrifty.

“They don’t gain weight as fast, and they don’t get to as large a size,” Fisher said. Blue Mounds’ yearlings average about 1,000 pounds. The dominant bull weighs more than a ton. “Apparently, it does make a difference in appearance and adaptability.”

A cattle-free strain could prove heartier in the face of climate change or disease.

The zoo converted its 12 bison to a pure conservation herd, bringing in animals from South Dakota’s Badlands and Oklahoma’s Wichita Mountains Wildlife Refuge. In 2012 it partnered with the DNR and started keeping a stud book for the state park herd.

Blue Mounds’ herd started in 1961 with three animals from Nebraska. Since testing started, cattle genes were discovered in three Blue Mounds animals. They were culled from the herd. Most recently, 2013 testing caught a bull brought in the previous year from Wichita Mountains in time.

“Today we have enough genetically pure bison that we can bring the species back,” Ingebretsen said. “Probably not to what it was — I mean the millions of animals that crossed the Great Plains is probably a pipe dream. I don’t think you’ll ever see that again. But we can certainly increase the number of genetically pure bison.”

Ingebretsen says, after all, “They’re a direct link to the past.”