1. Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina 27607, USA
2. Current address: Environmental Science, Policy and Management, University of California, Berkeley, California 94720, USA
3. Prairie Wildlife Research, PO Box 308, Wellington, Colorado 80549, USA
4. Department of Biological Sciences and Keck Behavioral Biology Group, North Carolina State University, Raleigh, North Carolina 27607, USA