1. Department of Fisheries and Wildlife SciencesVirginia Polytechnic Institute and State UniversityBlacksburgVirginia24061‐0321USA
2. U.S. Geological Survey, Virginia Cooperative Fish and Wildlife Research UnitVirginia Polytechnic Institute and State UniversityBlacksburgVirginia24061‐0321USA
3. Department of Biology and Environmental Studies Program, Randolph‐Macon CollegeAshlandVirginia23005USA