B. pinnicaudatus is a nocturnal, pulse type weakly electric fish. Males are larger than females and emit a longer duration, higher amplitude electric organ discharge (EOD), Sexual dimorphism in electric communication signals is used as a model for neurobiology and endocrinology, but the relevant behavior (e.g. mate choice) has been largely neglected. I conducted a series of unforced mate choice tests on gravid females in the lab. Females given a choice between a female and a male actively chose a male if he was relatively large. Females given a choice between large and small males chose larger males. Three correlated sexually dimorphic characters (body length, EOD duration, EOD amplitude) were larger for the chosen males. To dissociate these correlated male characters, I tested females on electric playback stimuli of large and small males. Results were inconclusive because female behavior changed over the period of the study.
