Why the brown ghost chirps at night

Since the pioneering work by Moeller, Szabo and Bullock, weakly electric fish have been widely used as a model to approach the study of both spatial and social cognitive abilities in a vertebrate taxon typically less approachable than mammals or other terrestrial vertebrates. Through their electric organ, weakly electric fish generate low-intensity electric fields around their bodies with which they scan the environment and manage to orient themselves and interact with conspecifics even in complete darkness. The brown ghost knifefish is probably the most studied species due to the large repertoire of individually variable and sex-specific electric signals it produces. Their rich electric vocabulary is composed of brief frequency modulations - or chirps - of the oscillating dipole moment constantly emitted by their electric organ. Because chirps come in different types, each carrying very specific and behaviorally salient information, they can be used as references to specific internal states during recordings - of either the brain or the electric organ - or during behavioral observations. Not surprisingly, this made the fortune of this model in neuroethology during the past 7 decades. Yet, truth is, this is not necessarily all true. Although established, to date this view has been supported only by correlative evidence and, to be fair, we still do not have a convincing framework to explain why these freshwater bottom dwellers emit electric chirps. Here we provide evidence for a previously unexplored role of chirps as specialized self-directed signals used to expand conspecific electrolocation ranges during social encounters.