1. Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, 0002 Pretoria, South Africa
2. World Wildlife Fund, Gallatin Gateway, MT 59730, USA
3. Department of Zoology, Stockholm University, SE-106 91 Stockholm, Sweden
4. US National Park Service, Western Arctic National Parklands, P.O. Box 1029 Kotzebue, AK 99752, USA