[1] Wolf Sci Ctr, Dorfles 48, A-2115 Ernstbrunn, Austria
[2] Radboud Univ Nijmegen, Dept Anim Ecol & Physiol, POB 9010, NL-6500 GL Nijmegen, Netherlands
[3] Max Planck Inst Sci Human Hist, Dept Linguist & Cultural Evolut, Kahla Str 10, D-07745 Jena, Germany
[4] Inst Psychol, Leutragraben 1, D-07743 Jena, Germany
[5] Univ Portsmouth, Ctr Comparat & Evolutionary Psychol, King Henry 1st Rd, Portsmouth PO1 2DY, Hants, England
[6] Univ Vet Med, Messerli Res Inst, Comparat Cognit, Vet Pl 1, A-1210 Vienna, Austria
[7] Univ Vienna, Med Univ Vienna, Vet Pl 1, A-1210 Vienna, Austria