FEMALE-FEMALE CONFLICT IN THE HAREM OF A SNAIL CICHLID (LAMPROLOGUS OCELLATUS): BEHAVIOURAL INTERACTIONS AND FITNESS CONSEQUENCES by GESINE BRANDTMANN 1) , MASSIMO SCANDURA 2) and FRITZ TRILLMICH 3,4) (Lehrstuhl für Verhaltensforschung,Universität Bielefeld, PO Box 10 01 31, D-33501 Bielefeld, Germany) (Acc. 19-I-1999) Summary Female intra-sexual competition plays an important role in the settlement process during pair or harem formation and in established harems of Lamprologus ocellatus , a small snail shell inhabiting cichlid from Lake Tanganyika. Larger females settle rst and this could partly be due to male preference for larger females as shown in simultaneous choice tests but is also due to dominance of the larger female. Smaller females were unable to settle close to a larger one. Even when snail shells were not limiting the smaller was either unable to settle or had to settle at a considerable distance. This effect was independent of prior residence.Intensefemale-femaleaggressionsuggeststhat close settlementis disadvantageous 1) E-mail address: Gesine.brandtmann@biologie.uni-bielefeld.de 2) Present address: Dipartimento di Scienze del Comportamento Animale e dell’Uomo, Via Volta 6, I-56126 Pisa, Italy. 3) Corresponding author; e-mail address: fritz.trillmich@biologie.uni-bielefeld.de 4) We wish to thank Uwe Kohler for giving us the sequence of three primers and him and Sigal Balshine-Earn for sharing their knowledge about Lake Tanganyika around Mpulungu with us. Barbara and Michael Taborsky were most helpful in establishing contacts with Zambia and provided advice as well as diving equipment for our eld work at Lake Tanganyika. Diethard Tautz and his group provided invaluable help in Munich by rendering possible the cloning and sequencing of L. ocellatus DNA in his laboratory. Toby Veall advised us where to nd L. ocellatus near his lodge and we thank him and Pippa Bailey and Russel Young for their marvellous hospitality at the Kalambo Falls Lodge and Walther Brandtmann and Sandra Kolberg for their much appreciated eld assistance. Edda Geißler kindly, and expertly, drew the graphs. This work was supported by the Deutsche Forschungsgemeinschaft grant TR 105/11-1 and the European Capital and Mobility grant ‘Ecology and Evolution of Mating Aggregations’ to FT. c ® Koninklijke Brill NV, Leiden, 1999 Behaviour 136, 1123-1144