1. Environmental Medicine Consortium and Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, USA
2. U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, AK 99508, USA
3. Centre for Wildlife Ecology, Simon Fraser University, 5421 Robertson Road, RR1, Delta, BC, Canada V4K 3N2