1. a Justus‐Liebig‐University Giessen, Research Centre for Bio Systems, Land Use and Nutrition , Department of Animal Ecology , Heinrich‐Buff‐Ring 26–32, 35398 Giessen, Germany
2. b University of Alaska Fairbanks, EWAHALE Laboratory, Biology and Wildlife Department , Institute of Arctic Biology , Alaska 99775‐7000, USA
3. c University of Vechta , Institute for Environmental Sciences , P.O. Box 1553, 49364 Vechta, Germany