1. Department of Biological Sciences; University of Alberta; Edmonton AB T6G 2E9 Canada
2. Ecosystem Science and Management Program; University of Northern British Columbia; 3333 University Way Prince George BC V2N 4Z9 Canada
3. Department of Renewable Resources; University of Alberta; Edmonton AB T6G 2H1 Canada
4. Norwegian Institute for Nature Research (NINA); Trondheim 7485 Norway