1. Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, Savoyenstraße, Vienna, Austria
2. Department of Cognitive Biology, University of Vienna, Althanstraße, Vienna, Austria
3. Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
4. Department of Biology, University of Florence, Via Madonna del Piano, Sesto Fiorentino (FI), Italy