1. Department of Biology, Acadia University, Wolfville, NS B4P 2R6, Canada.
2. Canada Fulbright Chair in Arctic Studies, University of Washington, Box 353650, Seattle, WA 98195-3560, USA.
3. Wildlife Research Division, Environment and Climate Change Canada, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
4. Department of Biological Sciences, University of New Brunswick, P.O. Box 5050, Saint John, NB E2L 4L5, Canada.
5. Department of Bioscience, Aarhus University, 4000 Roskilde, Denmark.
6. Greenland Institute of Natural Resources, Nuuk 3900, Greenland.
7. Norwegian Polar Institute, Fram Centre, P.O. Box 6606 Langnes, NO-9296 Tromsø, Norway.