1. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA
2. U.S. Geological Survey, Northern Rocky Mountain Science Center, Wildlife Biology Program, University of Montana, Missoula, MT 59812, USA
3. U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO 80526, USA
4. U.S. Geological Survey, Southwest Biological Science Center, Tucson, AZ 85721, USA