1. Program in Ecology, Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA.
2. Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA.
3. Department of Ecosystem Science and Management, University of Wyoming, Laramie, WY 82071, USA.
4. Wyoming Game and Fish Department, Jackson, WY 83001, USA.
5. Idaho Department of Fish and Game, Boise, ID 83712, USA.
6. Haub School of Environment and Natural Resources, University of Wyoming, Laramie, WY 82072, USA.
7. U. S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA.