1. National Wildlife Research Centre, Canadian Wildlife Service, Environment Canada, Carleton University, Ottawa, Ontario K1A 0H3, Canada, Pacific Wildlife Research Centre, Canadian Wildlife Service, Environment Canada, Delta, British Columbia V4K 3N2, Canada, Department of Biological Sciences, Centre for Wildlife Ecology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada, and Institute for Wildlife Studies, Arcata, California 95518