The Attack Frequency of Gnathonemus petersii towards Electrically Silent (Denervated) and Intact Conspecifics, and towards Another Mormyrid ( Brienomyrus niger)

1. Aggression experiments were performed with Gnathonemus petersii. Three kinds of stimulus fish were used in random order to elicit attacks: (1) intact conspecifics, (2) electrically silent (operated) conspecifics, and (3) the mormyrid Brienomyrus niger. 2. The aggression indices for the two experiments with B. niger and the intact conspecific, i,e. the two electrically active fish, were similar (p > 0.4), whereas the index for the experiment with the silent conspecific was about one half of the two others (p<0.01, Fig. 2). 3. In none of the three experimental conditions can the behavior sequence displayed by G. petersii be described by a random model, i.e. the occurrence of a given act depended on at least the preceding act (p