1. Department of Evolutionary and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
2. Department of Collective Behaviour, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell, Germany
3. Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Universitatsstrasse 10, 78464 Konstanz, Germany
4. Department of Integrative Biology, Michigan State University, 104 Natural Science Building, East Lansing, MI 48824-1115, East Lansing, MI 48824, USA
5. Division of Ecology and Evolution, Research School of Biology, Australian National University, 46 Sullivans Creek Road, Canberra, ACT 2600, Australia