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For years, southern Utah ranchers have worried about bison eating the grasses their cows depend on to survive the winter.

Turns out something closer to the ground may be bigger competition for the food: rabbits.

Utah State University researcher Dustin Ranglack spent two years studying the dynamics between the wild bison and cattle sharing the range in Utah's remote Henry Mountains. His research ended up focusing on a much smaller mammal and could lead to changes in long-held perceptions about competition between the herds.

In a study published Monday in the Journal of Applied Ecology, Ranglack showed that black-tailed jackrabbits and desert cottontails, not bison, are the main forage competitors for cattle in the Henry Mountains study area in Garfield County.

The discovery came as a bit of a surprise to Ranglack, a researcher with USU's Department of Wildland Resources and Ecology Center, state wildlife biologists and ranchers who have run cattle on the Henrys for generations.

"Bison are the most obvious presence on the landscape, other than cattle. They are big animals and they leave big dungs pats," Ranglack said. "But when you walk around, it becomes pretty obvious there is a fairly substantial jackrabbit population. You see a lot of pellets. It turns out rabbits were consuming twice as much forage as the bison."

Ranglack, along with his USU faculty mentor Johan du Toit and statistician Susan Durham, determined cattle consumed 52.3 percent of the grass biomass removed by herbivores in the study area. Lagomorphs — hares, rabbits and pikas — took out another 34.1 percent.

Bison accounted for 13.7 percent of the grass consumption.

Eighteen bison arrived on the Henry Mountains in 1941 after being transplanted from Yellowstone National Park and released in the Robbers Roost area of the San Rafael Desert. The animals moved to the Henrys and remain one of the few free-roaming bison herds in the country.

Ranchers with cattle in the Henry Mountains have had concerns about bison and aired them publicly with the Utah Division of Wildlife Resources through the years. Most rancher complaints have centered on the number of bison on the range and the wildlife agency's ability to accurately count the animals.

Ranglack and his crew built 40 "exclosures" in the study area. Half the structures kept bison and cattle from grazing on vegetation in the exclosure area. The other half also kept rabbits away from the grasses.

The team had predicted bison and cattle would be the top consumers of grass on the public rangeland in the Steele Butte North grazing allotment, about 20 miles south of Hanksville.

But the results took all the parties to a place few, if any, expected the discussion to lead: predators.

Surveys handed out by the researchers and returned from 12 of the of the 21 cattle producers in the study area (representing 3,556 of 5,019 grazing permits) before the project showed the ranchers believed bison were a high-level competitor to cattle. Rabbits were considered a low-level competitor.

At the same time, ranchers figured the Henry Mountains' coyote population should be controlled.

"I was concerned when I first presented this to the ranchers, because it was a little contrary to what had been said in the past," Ranglack said. "They really felt like bison were a problem and I was about to say otherwise."

During his presentation, Ranglack got to the part showing rabbits were the No. 2 forage consumer, and he didn't even need to mention coyote control.

"I heard them saying they needed to stop shooting coyotes," Ranglack said. "They jumped right to that conclusion on their own. I didn't have to say a word about it."

The study concludes: "The reduction or elimination of predator-removal programs may result in an increase in forage availability for wildlife and livestock."

Paul Pace, a fourth-generation rancher in the Henry Mountains, was at the meeting when the results were shared.

"We are not arrogant enough to think we know it all," Pace said. "The more we can do this type of legitimate research and not the chasing-the-dollar type of research, the better."

There are a lot of dynamics on desert allotments, he added. "Now we have observed this, the next question is: How does it play into management?"

Pace doesn't expect major changes in coyote control in the Henrys.

"Predator control is being done to protect the trophy deer herd," he said. "I don't see anybody worrying about controlling rabbits to help bison or cattle."

Bill Bates, wildlife section chief with DWR, said the bison in the Henry Mountains are doing well. Some have been relocated to the Book Cliffs of eastern Utah.

The post-hunting season population objective for bison on the Henry Mountains is 325 animals. The state averages about 70 hunting permits annually and roughly 1,000 hunters apply through a lottery for each available permit.

Ranchers, biologists and researchers all were equally surprised by the results of the study. Wildlife managers say the research has improved collaboration.

"Everybody was involved from Day 1 on this project," Bates said. "We have better communication and a better partnership with the livestock operators in that area as a result of the process. This has increased our ability to manage effectively."

The rabbits' variable life cycle complicates the management question after Ranglack's research. State and federal biologists estimate rabbit populations were below peak numbers during the study. That means the small mammals can have an even larger impact on the available forage base in the future if their numbers increase. On the other hand, their impact could go down when rabbit populations are low.

The "exclosures" are still on the mountain and could be used for additional research. Ranglack said the next step might be studying the impact of a controlled coyote population on rabbits.

"With appropriate ecological monitoring and adaptive adjustments, we believe livestock and wildlife can coexist and perhaps even benefit each other," Ranglack said. "For bison to be restored at ecologically meaningful scales in North America, they'll likely have to share rangelands with cattle. We think this balance can be achieved."

Twitter: @BrettPrettyman