Bison not cattle's top competitor for range forage, ecologists say

January 27, 2015 by Mary-Ann Muffoletto, Utah State University
Bison of Utah’s Henry Mountains are descendants of animals transplanted to the area from Yellowstone National Park in 1941. Utah State University ecologists, with support from the Utah Division of Wildlife Resources, are studying the free-ranging mammals, which are thought to be one of the few genetically pure groups of the species. Credit: Dustin Ranglack/Utah State University.

If bison lumber through a patch of rangeland, you'll know it, says Utah State University ecologist Dustin Ranglack. A mature bull, after all, often weighs a ton.

"Bison have a very conspicuous presence on the landscape," says Ranglack, who completed his doctorate in ecology this month in USU's Department of Wildland Resources and Ecology Center. "With their herding behavior, dust wallowing, trampling and big dung pats, they're hard to ignore."

So, for ranchers leasing Bureau of Land Management-owned land for grazing beef cattle in southeastern Utah's Henry Mountains, where Ranglack studies bison, it's logical to assume the large, free-ranging herbivores are the livestock's main competitor for forage.

But that's not the case, Ranglack says. The biggest consumer, he discovered after two years of study, is actually the much smaller, and less conspicuous, rabbit. With faculty mentor Johan du Toit, professor in USU's Department of Wildland Resources and Ecology Center and USU statistician Susan Durham, Ranglack published findings in the Jan. 26, 2015 issue of the Journal of Applied Ecology. The team's research was supported by the Utah Division of Wildlife Resources.

"As we started the study, we first met with ranchers to measure their perceptions of wildlife-livestock conflict in the Henry Mountains," Ranglack says. "Most felt bison were consuming more than their share."

The Henry Mountains bison are descendants of animals transplanted to the area from Yellowstone National Park in 1941 and thought to be one of the few genetically pure groups of the species. Challenges for the UDWR, which manages the bison, are determining how many of the animals live in the area in a given year, where they prefer to forage, the impact they have on available cattle forage and how many should be harvested during the hunting season.

In southeastern Utah’s Henry Mountains, Utah State University ecologist Dustin Ranglack stands near an exclosure used to study foraging behavior of bison and other herbivores. Credit: Melissa Ranglack/USU.

Also sharing the range are coyotes, about which the USU team also questioned ranchers. Most respondents supported continued efforts to curb coyote populations.

Ranglack and colleagues constructed 40 grazing exclosures in the conflict area to observe foraging behavior. Cattle consumed about 52 percent of the total grass biomass on the shared range, while bison ate about 13 percent. Lagomorphs – that is, jackrabbits and cottontail rabbits – gobbled up about 34 percent of the food.

"Because they're nocturnal and small, lagomorphs are less noticeable on the landscape," Ranglack says. "Unless you look closely – as we walked around shared grazing areas, we found rabbit pellets everywhere."

Looking at the big picture, the rabbits' proliferation comes into focus.

"With a reduced coyote population, lagomorph populations are likely higher than what we would expect naturally," Ranglack says. "Lagomorphs' nutritional needs also affect their choice and consumption of forage."

Pound for pound, rabbits eat much more than bison and the big-eared mammals need food of higher quality because they metabolize it quickly, he says.

"In contrast, bison can live on food of much lower nutritional quality because they digest their food so slowly," Ranglack says. "It takes up to 80 hours for grass to pass through a bison's digestive system, which gives plenty of time for nutrients to be absorbed."

The next step for study, he says, is the impact of a controlled coyote population on lagomorph densities. To accomplish this, the team will continue to monitor exclosure sites.

"With appropriate ecological monitoring and adaptive adjustments, we believe livestock and wildlife can co-exist and perhaps even benefit each other," Ranglack says. "For 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."

Explore further: Bison transferred to reservation from Yellowstone

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5 / 5 (1) Jan 27, 2015
Confirmation that actual real time observation trumps what would appear to be obvious.
5 / 5 (1) Jan 27, 2015
settlers of the American West dutifully slaughtered about 22 million head of Bison, mostly during the 19th century, so they could raise European cattle and horses instead. what a monumental waste of a natural resource. conservationists would be piously outraged if some other country did that to an endemic or endangered species today, as IS being done to many species in Africa and Asia.
5 / 5 (1) Jan 27, 2015
Does this mean that the ranchers and cattlemen will have to admit their bias, and take a different path towards the re-establishing a coyote population, so as to control the rabbits in a more proper manner, as Mother Nature intended? Or will they just sponsor lotteries to obtain permits to gang-shoot the rabbits; perhaps allowing hunts by helicopter, equipt with FLIR, and using Night Vision Scopes. I realize that this is only ONE study, but it seems well researched and convincing to me. Besides the big business ranching industry has had its hands out; offering bribes to the Federal Government for years.
1 / 5 (1) Jan 28, 2015
. . . and how many should be harvested during the hunting season.

"Harvested" is such an interesting synonym. While pondering over the reason it is used to describe the activity I thought: maybe the world would seem a less stressful place if its use were more widespread.

We could talk of some number of soldiers harvested on a battlefield in Afghanistan. In angry confrontations, enraged individuals might be inspired to commit acts of voluntary harvesting. That bloodbath in Paris could instead be referred to as a bountiful harvest. All those hapless children in that school in Pakistan - harvested. Thousands of automobile drivers involuntarily harvested each year by others harvesting while intoxicated. Russians and Ukrainians harvesting each other in their conflict. There sure is a lot of harvesting going on in the world!

There. Don't we all feel better now?

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