Centre for Wildlife Ecology, Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada; Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA; and Pacifi c Wildlife Research Center, Canadian Wildlife Service, Environment Canada, Rural Route 1, 5421 Robertson Road, Delta, British Columbia V4K 3N2, C...