1. Laboratoire d'Ethologie Expérimentale et Comparée E.A. 4443 (LEEC) Université Paris 13 Sorbonne Paris Cité F‐93430 Villetaneuse France
2. Department of Animal Physiology University of Bayreuth D‐95440 Bayreuth Germany
3. Institute of Animal Science University of Hohenheim D‐70599 Stuttgart Germany