1. Department of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71C, 60-025 Poznań, Poland
2. Konrad Lorenz Institute of Ethology, University of Veterinary Medicine Vienna, Savoyenstraße 1a, 1160Vienna, Austria
3. Department of Behavioural and Cognitive Biology, University of Vienna, University Biology Building, Djerassiplatz 1, 1030 Vienna, Austria
4. Istituto Sperimentale Zootecnico per la Sicilia, via Roccazzo 85, 90135Palermo, Italia