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."