A government-funded experiment on diseased bison herds in Yellowstone National Park shows non-infected animals can be safely removed and used to start new herds, researchers from the U.S. Department of Agriculture and a wildlife group said Thursday.
The results bolster arguments that a species driven to the brink of extinction last century could be restored to parts of its once-vast territory without threatening livestock with disease.
Yellowstone's bison are prized for their pure genetics. About half of them test positive for exposure to brucellosis, which causes pregnant animals to prematurely abort their young.
Government workers captured and slaughtered thousands of migrating bison over the past two decades to prevent them from coming into contact with cattle herds in Montana. The practice has resumed this winter under a state-federal agreement that calls for controlling the migration and maintaining their population at about 3,000 animals.
By capturing and putting park bison into quarantine, the animals could be declared brucellosis-free within three years, or even sooner with calves and male animals, according to researchers from the U.S. Department of Agriculture's Animal and Plant Health Inspection Service and the Wildlife Conservation Society.
Advocates say that means Yellowstone could be used as a supply source for establishing bison herds on public and tribal lands across the West.
More than 200 bison were captured and used in the experiment, which was carried out in partnership with Montana wildlife and livestock officials.
Some bison were killed for testing or after infections appeared. About 60 animals and their offspring remained disease-free and were transferred to tribes on the Fort Peck and Fort Belknap Indian Reservations. The remaining bison are being held on a ranch near Bozeman owned by media mogul Ted Turner until a permanent home is found.
"This will help defuse the argument about brucellosis, that the animals are carrying brucellosis and will give it to cattle around them," said wildlife pathologist Jack Rhyan of the health inspection service. "I'll feel more positive after 1,000 animals have gone through. That's just caution because this disease sometimes crops up where you never think it can."
Efforts to relocate or provide new habitat for the park's surplus bison have stalled recently in the face of livestock industry opposition. Besides concerns over disease, ranchers complain that the animals knock over fencing and eat grass that could otherwise go to cattle.
Yellowstone biologists counted 4,600 bison in the park last summer.
More than 200 have been killed this winter by hunters, according to Montana Fish, Wildlife and Parks.
Another 145 animals have been sent to slaughter, and 33 were transferred into another health inspection service experiment dealing with animal contraception, Yellowstone spokesman Al Nash said.
Capture operations typically last until mid-March, when pregnant female bison are getting close to delivery and bison begin moving back into the park as it greens up with early spring weather, Nash said. That could change depending on weather in coming weeks.