HANKSVILLE, Wayne County — A four-footed remnant of the wild, wild West lives on in a remote mountain range in southern Utah.
New genetic tests confirm what has long been suspected: a herd of bison in the Henry Mountains is one of the few surviving populations of pure American plains bison, a species that once dominated the Great Plains and the western United States by the millions.
"When I say 'pure' I mean bison that have not been contaminated with cattle genes," said professor Johan du Toit of Utah State University's Department of Wildland Resources. "Most of the bison that are around today, particularly those on private land, are hybrids."
The absence of cattle genes is not due to a lack of cross-breeding opportunities. The Henry Mountains bison roam freely in an area south of Hanksville where domestic ranch cattle also graze under permits from the Bureau of Land Management. In spite of that close proximity, it appears there has been no inter-breeding in the seven decades the bison have been there.
Perhaps just as important: The Henry Mountains bison herd shows no signs of brucellosis. That disease has sparked decades of conflict with ranchers near Yellowstone National Park as purebred bison there have wandered out of the park in wintertime.
Now that the Utah herd is shown to be not only purebred but disease-free, the herd could play a primary role in bringing back a magnificent species that was nearly wiped out in the 1800s.
"The Henry Mountains bison have been an enigmatic population of bison in North America for a long time," du Toit said.
The vast bison herds of ancient North America — often called "buffalo" by nonscientists — were hunted nearly to extinction in just a few years in the late 1800s. The Yellowstone herd descended from just a few survivors. Later, a few Yellowstone bison were transplanted to Utah and turned loose in a remote desert area called Robber's Roost about 50 miles from the Henry Mountains.
"They were brought down from Yellowstone in the 1940s," du Toit said, "and they made their way, on their own, into the Henry Mountains, which is land that is managed by the Bureau of Land Management. So that's public land."
Hundreds of thousands of bison live around the country in various public and private settings, du Toit said, but nearly all of them carry cattle genes. Even the well-known bison on Antelope Island in the Great Salt Lake have domestic cattle as ancestors, according to du Toit. The hybrids around the country mostly resulted from cross-breeding experiments by ranchers who hoped to combine the toughness of bison with the docility of cattle.
It's well-known that bison will cross-breed with cattle when bulls are confined inside fences with cows. The question researchers at USU and Texas A&M University set out to answer is whether cross-breeding takes place in the wilds of the Henry Mountains, where the "buffalo" roam and where ranch cattle often sidle right up alongside them. So the researchers collected hair samples and tiny chunks of ear tissue from the skittish bison.
"We managed to get samples from 129 animals," du Toit said. "The population's about 350 animals, so we sampled about one-third of the entire population."
The DNA findings suggest that when bison roam free and have each other to mate with, they aren't much interested in getting cozy with cows.
"We were actually able to determine that there was no evidence of cattle DNA in all of those samples," du Toit said.
It's not exactly a surprise, but it is a cause for celebration, he said. "Now we know they are genetically pure. But the other thing is that they are disease-free."
Unlike the purebred herd at Yellowstone, the Henry Mountain herd shows no signs of brucellosis, a disease that causes spontaneous abortions and can be spread to cattle and elk. It's the primary reason ranchers near Yellowstone have campaigned for bison to be killed or captured if they wander out of the national park.
The disease-free, genetically-pure Utah herd could become valuable if other states use it to launch their own herds.
"It confirms that you can have bison and cattle, free ranging, together," du Toit said. "The other really good thing for Utah is that we have here an extremely valuable source of biodiversity."
Some experts have argued that restoring bison herds in some places would be good for the environment due to the "tilling" effect of bison hooves and the fertilizing properties of their dung and urine.
"In areas where bison can be introduced," du Toit said, "it's being argued by ecologists that bison are probably very important in terms of maintaining ecosystem function."
The DNA testing is part of a larger study commissioned by the Utah Division of Wildlife Resources. The agency is exploring the best methods for managing cattle and bison together in the same area.