Effects of sex, sensitivity and status on cue recognition in the weakly electric fish Apteronotus leptorhynchus

Maintaining a stable social organization necessitates that animals recognize their own dominance status relative to the status of other group members. The weakly electric brown ghost knifefish emits a sexually dimorphic sinusoidal electric organ discharge (EOD) for electrolocation. Dominant males discharge at the highest and females at the lowest EOD frequencies (EODFs). Each individual is most sensitive to its own EODF, which can be modulated for communication. To examine how sensitivity and social status influence an individual's response to different cues, we recorded the electrical signals emitted by 10 males and seven females in response to playbacks of sine waves mimicking a wide range of con- and heterospecific EODFs. While all individuals emit small chirps (LoCs) mostly to stimuli around their own EODF, they are more likely to emit rises (gradual nonchirp signals) to frequencies to which they are less sensitive; males similarly emit larger chirps (HiCs) to frequencies more distant from their own, especially to female mimics. Males with ‘dominant’ EODFs are less likely to emit rises, stimuli in the female range elicit more rises from both sexes, and females emit rises to male EOD mimics. Although low-ranking male EOD mimics elicit more LoCs from all males, males with lower-ranking EODFs chirp less at high EOD mimics than males with high-ranking EODFs chirp at low EOD mimics. We conclude that (1) although much of the variation in an individual's response is attributable to its sensitivity, individuals recognize sexual and status cues and have some internal representation of their own social status, and (2) whereas LoCs appear to function in intrasexual aggression, HiCs and rises could be used in both courtship and submissive signalling. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.