Résumé
Social animals may reduce their overall metabolic demand through group living due to a “calming effect”. However, it remains unclear whether the metabolic response of individuals to group members varies depending on the social system, and how individual sociability influences this response. We measured the metabolic rates of the territorial three-striped dwarf cichlid (Apistogramma trifasciata) and the shoaling cardinal tetra (Paracheirodon axelrodi) in the presence or absence of three conspecifics, examining the relationship between individual sociability and metabolic rates, with a focus on how sociability influences the metabolic response to conspecific presence. Territorial cichlids exhibited increased standard metabolic rate (SMR) and routine metabolic rate (RMR) in response to the presence of conspecifics, while shoaling tetras showed unaltered RMR or SMR. In tetras only, sociability was negatively correlated with both SMR and RMR, but this relationship weakened when conspecifics were present—indicating that metabolic responses to conspecific presence differ among individuals of varying sociability. The contrasting metabolic responses to grouping in these species demonstrate that the energetic consequences of social proximity depend on the species’ evolved social structure. Given the lack of correlation between individual sociability and metabolic rates in cichlids, we suggest that sociability and maintenance metabolism may evolve independently, without underlying genetic covariation. This study highlights the intricate relationship between group living and individual energy expenditure, indicating that a species’ social system plays a significant role in determining the extent to which the metabolic response to social partners serves as an adaptive element of group living.