1. Centre for the Advanced Study of Collective Behaviour, University of Konstanz, 78457 Konstanz, Germany
2. Department of Collective Behaviour, Max Planck Institute of Animal Behavior, 78457 Konstanz, Germany
3. Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057 Zurich, Switzerland
4. Department of Psychology, University of Konstanz, 78457 Konstanz, Germany
5. Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, ACT 2600, Australia