1. Cognitive and Cultural Ecology Research Group, Max Planck Institute of Animal Behavior, Radolfzell, Germany
2. Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany
3. Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
4. Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australia
5. Department of Collective Behavior, Max Planck Institute of Animal Behavior, Konstanz, Germany