Whats more, bison road use peaked in the months before and after the roads were groomed, especially after mid-April when spring thaws opened up new foraging areas.
Its not even a fifty-fifty, on-road/off-road split. Its so much lower than that, Bjornlie said. The majority of movement is off road.
The results challenge several assumptions about the ecological role of groomed trails on bison survival and behavior.
For example, the study yielded no evidence that the animals use groomed roads for travelling long distances. Most--68 percent--travelled less than 1 kilometer while on groomed terrain. Ive seen them walk from a streambed up to a road, walk 500 to 600 meters along the road, then go off into another streambed, Bjornlie said. Its part of their travel. They definitely use them [groomed roads], but they are part of a much larger travel network that includes off-road travel.
The study instead documented heavy travel over the Mary Mountain Trail linking the Hayden Valley, where many of the animals in the study spend the summer, to the Firehole area, where the majority of them winter. Using infrared monitoring stations, Bjornlie recorded between 100 and 700 bison events in a two-week period along the trail.
Visitors to the park more than 100 years ago told of bison following the same trail, suggesting to Bjornlie that the nomadic animals re-established the migration pattern once their numbers began rebounding. When population control efforts ceased in 1967, there were about 400 bison in the park. Before the big die-off in 1996-97, there were about 3,500.
So theyre moving because of range expansion, not because of the roads, Bjornlie said.
Park spokeswoman Cheryl Matthews said data collection on bison movement in the park will continue. Because the park hasn't yet experienced another winter as harsh as the 1996-97 one, when so many bison left the park and were shot, data from
'"/>
Contact: Annette Trinity-Stevens
annettet@montana.edu
406-994-5607
Montana State University
3-Jan-2001