Comparative studies of the aggressive behaviour of two gymnotid electric fish (Gymnotus carapo and Hypopomus artedi).

Electrical and motor behaviour was studied during aggressive interactions in two species of electric fish (Gymnotus carapo and Hypopomus artedi). Paired comparison methods were used to obtain the data, and analysis of the results was undertaken at three different levels: (1) The repertoire of behaviour (motor and electrical); (2) The changes in relative frequency of components with increasing exposure to conspecifics; (3) Sequential analysis of patterns of behaviour occuring both within and between individuals. The results of the three analyses showed: (1) A great similarity in repertoire although a much higher rate of interaction for Gymnotus. The relative importance of the "off" and "burst" signals was reversed for the two species. A prolonged orientation component in Hypopomus was found to be related to the occurrence of discharge synchrony. (2) Habituation of intense components in favour of electrical signalling in both species. (3) Important differences in both the length and structure of sequences.