1. New Mexico Cooperative Fish and Wildlife Research Unit, New Mexico State University, PO Box 30003, MSC 4901, Las Cruces, New Mexico 88003, USA
2. US Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, Department of Fish, Wildlife, and Conservation Ecology, New Mexico State University, PO Box 30003, MSC 4901, Las Cruces, New Mexico 88003, USA