1. Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand , Private Bag 3, Wits 2050 , South Africa
2. U.S. Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, Department of Fish, Wildlife, and Conservation Ecology, New Mexico State University , Las Cruces, NM 88003 , USA
3. Department of Biological and Environmental Sciences, Texas A&M University-Commerce , Commerce, TX 75428 , USA