For Prairie Conservation, Bison Serve as Tools

Nov 1, 2016

A herd of bison graze at Dunn Ranch Prairie in Harrison County, Missouri.
Credit Sebastián Martinez / KBIA

On a recent Friday morning, a group of about 20 Nature Conservancy Trustees, visitors and staff have gathered for a tour of the conservancy’s Dunn Ranch Prairie. The Nature Conservancy is an international non-profit focused on conservation, and its Missouri director Adam McLane is on hand for the day’s tour.  

The prairie covers more than 3,000 acres and is host to a dizzying variety of native insects and birds, but on this morning, the tour group gathered to see its most imposing inhabitants: bison.

The visitors loaded up onto a flatbed trailer with bleachers on board. A tractor then hauled them out to the prairie, with Dunn Ranch site manager Randy Arndt, at the helm.   

"Dunn Ranch is about 3,600 acres-3,400 acres, we purchased it in 1999," Arndt explained. He continued, "In 2004 there was less than 19 percent of the area was in native vegetation. Since then we’ve replanted more than 2,500 acres of prairie. 99 percent of Dunn ranch is now in native vegetation."

Dunn Ranch site manager Randy Arndt (center) speaks to a tour group at the prairie, as Nature Conservancy State Director Adam McLane looks on.
Credit Sebastián Martinez / KBIA

The ranch is the focal point of an overarching restoration project called the Grand River Grasslands. Arndt said the conservancy envisions the project as a network of privately managed working grasslands anchored by core areas of high quality prairie like Dunn Ranch. After entering the bison enclosure, the tractor came to a halt. Arndt described the bison at the prairie as key to the mission.

"The main reason we have our bison are to be used as a tool to manage the prairie … And create the structure, the openness and differences of height that we need for the various suites of grassland birds," Arndt said.

Bison are closely related to cattle, and can even interbreed. This has led to extensive hybridization, and the issue of bison genetics can be surprisingly controversial. But in terms of behavior, the bison at Dunn Ranch are a world away from their bovine predecessors there. Instead of grazing mowing down all the plant life, bison selectively focus graze on grasses, leaving wildflowers and good habitat for native birds. And, because bison have lived on the prairie for millennia, their behavior is intricately tied to the plants on which the wildlife relies.

Bison graze in small family groups during the day, re-joining the larger herd when threatened.
Credit Sebastián Martinez / KBIA

"When you see them, you look at them, their fur is just full of seed," Ardnt said. "And then they’ll come over here and say, ‘oh I’m gonna flop on the ground and dust.’ And he does his thing there, and in the meantime that seeds flying out of his fur so he takes the seed from over there and plants it over here."

As the trailer winds through the prairie, Arndt points out an area that makes the unique makeup of Dunn Ranch unique.

He explained, "Everything you see to the south and west is the un-ploughed portion of the prairie, there’s about 1,000 acres there. It still has all the characteristics of the original prairie, it’s got 40 inches of black topsoil, over 300 species of native plants."

Arndt said he suspects the rough topography of the land saved it from being ploughed under like so many other areas of prairie in the state. With 99 percent of the original prairie in Missouri gone, Arndt says the thousand-acre patch of un-ploughed land at Dunn Ranch represents the largest such area in the whole six-state ecoregion. 

An eye-catching sign warns would-be hikers about the resident bison herds.
Credit Sebastián Martinez / KBIA

This patch has served as a refuge for countless native insect species, including ants that have since re-colonized the re-planted areas of the ranch, as well as bees, which are conservation coordinator Hilary Haley’s specialty.

"For here we could expect to see maybe 200 to 300 species of native bees and so far I’ve collected 110 species just from this area," Haley said.

Including some surprises. "We have found four new species to the state, here at Dunn Ranch, we also have a species that hasn’t been identified so far." She explained, "We’re thinking that it could be new to science, but that’s really not known yet."

The scarcity of un-ploughed prairie makes Dunn Ranch a potentially valuable site for researchers who specialize in prairie, and other grassland ecotypes.

"We have a tremendous amount of opportunity here to open up Dunn Ranch to be a sort of living laboratory for people to come in and understand better the native system that is here," Haley said.

After a winding and windy ride, the trailer pulled alongside a dozen or so bison, spooking them into rejoining the larger herd a hill over. 

Bison calving season is in May, but one calf was born a month ago in September, and its bright orange fur stood out among the herd. The tour group excitedly crowded around one side of the trailer, taking pictures of the bison, which jumped and played with one another.

Arndt exclaimed, "They’re feeling pretty frisky today, they hardly ever run around like this!"

The conservancy keeps the herd to around about 100 bison, selling off excess bison to other conservation projects or at auction. After watching the herd for a few minutes, the tractor started the journey back to the ranch’s visitor center, leaving the bison to their work of conserving the prairie.