Mbuna-cichlids (Lake Malawi, Africa) are very closely related to each other. They form a very complex community with a density of 7 animals or more/m². Therefore we can make the assumption that there are interspecific behavioural relationships in the Mbuna-group.

In order to find out whether there is a communication system between different Mbuna-species we have started a study of the intra- and interspecific behavioural relationships in four Mbuna species (Melanochromis auratus, M. johanni [sic], Pseudotropheus « ornatus », P. lombardoi).

The intraspecific study pointed out that all four species have a linear rank order, which answers to strict rules:

— the hierarchy is absolute, i.e. a subordinate animal will never or very rarely act aggressively towards a dominant animal when the hierarchy is stable,
— the number of aggressive interactions between two group members is determined by the rank number of the actor and reactor,
— most interactions occur between rank neighbours (does not count for P. lombardoi).

The four species do differ in frequency of the different agonistic acts. The interspecific study started with putting together two different species. In such interspecific groups linear rank orders were formed. In these hierarchies the original intraspecific rank order and coloration were retained.