1. Fish and Wildlife Management Program, Biology Department, Montana State University, 310 Lewis Hall, Bozeman, Montana 59717, USA (e-mail: )
2. National Council of the Paper Industry for Air and Stream Improvement, Forestry and Range Sciences Lab, 1401 Gekeler Lane, La Grande, Oregon 97850, USA
3. Department of Population Health and Reproduction, University of California, Davis, California 95616, USA
4. ZooMontana, P.O. Box 80905, Billings, Montana 59108, USA
5. Pacific Northwest Laboratory, P.O. Box 999, Richland, Washington 99352, USA
6. Department of Mathematical Sciences, Montana State University, Bozeman, Montana 59717, USA