Courting and fighting quietly: a lack of acoustic signals in a cooperative Tanganyikan cichlid fish

Research on cichlid fishes has revealed remarkable cross-species variation in social and reproductive behaviour. Recently, several species of African cichlids have been shown to produce acoustic signals, typically in conjunction with the visual behavioural displays associated with mate choice and competition. However, the recent research conducted on cichlid sound production has focused largely on polygynous cichlids with female-care and on species from Lake Malawi and Lake Victoria. In this study, we examined whether sound production occurs in a group-living cooperative biparental cichlid species, Neolamprologus pulcher, endemic to Lake Tanganyika, the oldest of the African Great Lakes. N. pulcher is a highly social cichlid that lives in complex groups that are socially stratified. We investigated whether N. pulcher performed acoustic signals to each other either during competitive resource contest trials between size-matched males, or during courtship trials between male and female breeding pairs. Although the fish displayed prototypical visual displays of aggression, submission, and courtship in the appropriate context, we found no evidence of vocal sound production. Our findings suggest that cichlid sound production was not essential for the evolution of complex social behaviour.