for National Geographic News
As winter snows approach Yellowstone National Park, many federally protected bison will soon wander outside the park in search of food across the border in Montana.
When they do, the bison will encounter something they haven't seen in 15 years: hunters.
Today Montana reinstated bison hunting in what the state says is an effort to contain the possible spread of brucellosis, a disease some bison carry, to Montana's cattle.
The sight of bison being shot is likely to set tempers flying, as it did when the hunt was last carried out in 1990.
"We know there is going to be a negative reaction," said Ron Aasheim, spokesman for Montana's Department of Fish, Wildlife and Parks.
"But we are charged with minimizing the risk of brucellosis to cattle, and this is a tool we are going to use."
At an Impasse
Montana's bison hunt is the result of two modern scientific miracles, which now stand at odds with one another.
One is the resurrection of the bison, perhaps the most iconic of American mammals, from near extinction.
The other is the virtual eradication of brucellosis. The disease can cause female bison, cattle, and elk to abort their fetuses. It can also be passed to humans, causing a chronic ailment known as undulant fever.
The U.S. Department of Agriculture has spent almost three billion dollars over the last 70 years trying eliminate the disease.
Once present in nearly all of the United States, brucellosis has been eliminated in cattle in all but two states: Texas and Wyoming. It remains most prevalent among Yellowstone's bison and elk.
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