1. Department of Biology and Wildlife, Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775 USA
2. Biology Department MS-34, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543 USA
3. U.S. Geological Survey, Patuxent Wildlife Research Center, 12000 Beech Forest Road, Laurel, Maryland 20708 USA
4. U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508 USA
5. Canadian Wildlife Service, 5320 122 Street NW, Edmonton, Alberta T6H 3S5 Canada