1. Department of Zoology, University of Western Ontario, London, Ontario N6A 5B7, Canada
2. Canadian Wildlife Service, 152 Newbold Court, London, Ontario N6E 1Z7, Canada
3. Department of Biological Sciences, University of Idaho, Moscow, Idaho 83843 USA
4. Department of Zoology, Washington State University, Pullman, Washington 99164-4220 USA