1. Cognitive and Cultural Ecology Research Group, Max Planck Institute of Animal Behavior, Am Obstberg 1, 78315 Radolfzell am Bodensee, Germany.
2. Taronga Institute of Science and Learning, Taronga Conservation Society Australia, Bradleys Head Rd, Mosman, NSW 2088, Australia.
3. Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany.
4. Department of Biology, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany.
5. Australian Museum Research Institute, Australian Museum, 1 William Street, Sydney, NSW 2010, Australia.