June 4, 2005

Study Looks at Yellowstone Roads and Bison

BILLINGS, Mont. -- Roads groomed for snowmobiles and snowcoaches in Yellowstone National Park are not the key factor influencing bison distribution and numbers in the park, a researcher said Friday.

"The roads very definitely make it easier for bison to move along the landscape, but we didn't see an overall effect on distribution or population increases," said Cormack Gates, director of the Environmental Science Program in the Faculty of Environmental Design at the University of Calgary.

Gates, an expert in bison ecology and management, said bison distribution seems to be driven by density, or bison numbers. More bison use more space, and their quest for food - particularly in heavy snow years - helps push them to the park boundaries, he said.

The study looked at the effects of groomed roads on bison in Yellowstone. Some environmentalists and others have contended groomed trails facilitate bison movement in the park and contribute to bison being killed as they leave the boundaries and enter Montana, where ranchers worry bison could transmit brucellosis to cattle. Brucellosis can cause cows to abort.

A joint state-federal plan allows for the hazing and capture of bison that wander from the park, and testing of the animals for brucellosis. Bison testing positive are slaughtered.

D.J. Schubert, a wildlife biologist with The Humane Society of the United States, said late Friday he hadn't yet read the full report. But he said he believes there would be a very different situation for bison in the park now if roads had never been groomed.

"Ending road packing in all or most of the park is a sensible step to addressing this ongoing brucellosis crisis," he said.

The report makes several recommendations, including that the park implement a bison population monitoring program and define a minimum viable population for the northern range. It also suggests an experiment to test the effect of snow conditions on a section of road connecting the central and northern parts of the park, he said.

Yellowstone spokeswoman Cheryl Matthews said the report will be taken into account by National Park Service officials as they prepare a long-term plan for winter use in Yellowstone and Grand Teton national parks.


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