Interactive electrical behaviour in mormyrid weakly electric fish: Jamming avoidance response or social interaction?

Weakly electric fish emit electric organ discharges (EODs) for both active electrolocation and electrocommunication. In African mormyrids, pulse-type EODs are produced at highly variable inter-discharge intervals (IDIs), forming sequences that can convey contextual and behavioural information to conspecifics. Neighbouring fish frequently engage in time-locked interactive behaviours, such as fixed-latency echo responses and EOD synchronisation. These behaviours have been proposed to function either as a jamming avoidance response (JAR), preventing simultaneous discharges and interference with electrolocation, or as a form of social signal. To test these hypotheses, we analysed interactions between pairs of Mormyrus rume proboscirostris, quantifying EOD synchronisations, echo events, and instances of jamming. Our results show that jamming is rare in this species. We found no correlation between jamming frequency and echoing behaviour, nor evidence that synchronisation and echo events are direct responses to recent jams. Instead, these interactive behaviours were associated with specific movement patterns and social contexts. Synchronisations were mainly initiated by stationary hovering individuals, while echo responses were more frequent in smaller fish actively following a social partner, suggesting a role in leader-follower dynamics. Pairs with more frequent echoing also exhibited reduced inter-individual distances, indicating that interactive electrical signalling promotes social cohesion. Rather than mitigating jamming, interactive electrical behaviours in mormyrids likely serve as communicative strategies to maintain group coherence or allocate social attention. These findings highlight the role of electrocommunication in structuring social interactions. Investigating the rules of these behaviours could eventually decipher which specific IDI patterns signal social intent and help to understand the underlying mechanisms of electrocommunication. HighlightsO_LIMormyrid fish frequently perform interactive signalling during electrocommunication. C_LIO_LIInteractive electrical signalling is associated with specific locomotor behaviours. C_LIO_LIEcho responses and signal synchronisations are not linked to jamming. C_LIO_LISignal synchronisations may support mutual assessment upon encounters. C_LIO_LIInteractive signalling promotes social cohesion and leader-follower dynamics. C_LI